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Physical characterization of the frozen fragments of the Tagish Lake

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1. 140 31 32 Other designs tested during the third test included a single thermal blanket two thermal blankets and a lab coat two thermal blankets a lab coat and a thermal blanket draped over the set up and heating pads under a single thermal blanket The heating pads are paper bags filled with several reagents whose strongly exothermic reaction is triggered by exposure to air Unfortunately the heating pads were too weak and unpredictable to be used a primary method of protection Nevertheless some were taken to Edmonton as they can be useful as secondary protection in for example leaky areas The fourth test verified that the optical performance of the camera did not change with temperature It involved scanning a flat calibration object As the result ing 3D point cloud must correspond to a two dimensional plane Principal Compo nent Analysis PCA can be used to fit a plane to it Mah et al 2013 If the camera s optics remain stable as the temperature changes there should be no correlation be tween the temperature and the standard deviation of the fitted plane from the 3D point cloud The results of this test are shown graphically in Figure 9 By inspection it is clear that there is no relationship between temperature and the standard deviation In the fifth test some analogue samples were scanned The purpose was to de termine if the overall quality of the scans would be similar to the ones made at room temperatu
2. C M O D Gyngard F Nittler L R Cody G D Fogel M K Kebukawa Y Kilcoyne A L D Hilts R W Slater G F Glavin D P Dworkin J P Callahan M P Elsila J E de Gregorio B T Stroud R M 201 1a Origin and evolution of prebiotic organic matter as inferred from the Tagish Lake meteorite Science 332 1304 1307 Herd C D K Hilts R W Simkus D N and Slater G F 2011b Cold curation and 59 handling of the Tagish Lake meteorite implications for sample return abstract 5029 The Importance of Solar System Sample Return Missions to the Future of Planetary Science Herd C D K 2013a The Tagish Lake Meteorite A Touchstone for Understanding Interstellar Nebular and Parent Body Processes abstract 5313 76th annual Meteoritical Society meeting Herd C D K 2013b Personal communication Herd R K and Herd C D K 2007 Towards systematic study of the Tagish Lake meteorite abstract 2347 Lunar and Planetary Science Conference XX XVIII Herd R K 2013 Personal communication Hildebrand A R McCausland P J A Brown P G Longstaffe F J Russell S D J Tagliaferri E Wacker J F and Mazur M J 2006 The fall and recovery of the Tagish Lake meteorite Meteoritics and Planetary Science 41 407 431 Hilts R W Shelkhorne A W Herd C D K 2012 Creation of a Cryogenic Inert Atmosphere Sample Curation Facility Establishing Baselines for Sample Return Missions abstract 5352 75th a
3. and 40 taped to it was used instead see Figure 1 Usually samples are rotated in increments of 20 for three different orientations for a minimum of 54 scans Often extra scans were added to cover any areas with a particularly difficult geometry such as occlusions and narrow depressions These scans provide a comprehensive library that cover the entirety of the meteorite surface Usually a meteorite s model can be assembled in less than 15 scans easy geometry or surface texture reduces the amount of scans necessary As Tagish Lake must be imaged in a cold room under time constraints performing as many as 60 scans was not always a feasible option The number of scans taken for each sample is noted in Appendix B Finally when the scanning is complete a three 12 Figure 1 A swivel base with a diameter of 10 inches was used to construct a manual turntable for use in the cold room to minimize the need to transport and use electronic equipment Markings denoting 20 30 and 40 increments were added and a foam piece was taped to the bottom for reference In this illustration a piece of coal that was used to simulate the Tagish Lake meteorite has been placed on the turntable 13 dimensional model is assembled using InnovMetric s PolyWorks software The program allows the operator to align the scans into a watertight 3D model Once the model is created Poly Works has a function that calculates the bulk volume of the model As th
4. 2 and to close out the first run on July 5 41 42 Favourable geometry involves many salient features and and edges that are not toosharp but not too smooth which makes it easier for the software to align the indi vidual scans and for the human operator to guide the process The better the fit be tween two scans the lower standard deviation between them When the entire model is assembled the Polyworks software calculates the overall standard deviation for the model Specifically the standard deviation represents the alignment error in mm be tween all of the points Per Figure 12 standard deviation does not show a trend with bulk volume A model with a lower standard deviation is easier to assemble and more reproducible hence the bulk volume measurement derived from it should be consid ered more precise Based on previous studies the best case standard deviation is ap proximately 0 050 mm For this standard deviation the uncertainty was liberally set at 1 and it would change proportionally from this value For example the uncer tainty at a standard deviation of 0 10 mm is twice that of at 0 050 mm thus 2 The uncertainty in the value for porosity was also propagated by quadrature It depends on the uncertainty in bulk volume and grain volume The equation for porosity is reworked from equation 2 Substituting the definitions of density into the equation i MIV 14 1 MIV 14 The mass of the meteorite is eliminate
5. C were 25 used to monitor the temperature on either side of the camera as per Figure 6 While their accuracy is not great it was sufficient for the intended purposes Furthermore the type K thermocouples are well within their measuring range below 0 C which was useful when checking the temperature of the cold room to compare with the cold room thermometer readings Thermocouple sensor area Light receiving lens 26 Figure 6 The laser camera is prepared for the cold room This photograph shows the last step before it is wrapped with thermal blankets Foam pads 1 8 are placed on the corners to create an insulating layer of air Pads 9 and 10 are placed over the laser emitting windows and light receiving lens respectively so they are not obstructed Finally a probe thermocouple type K is secured to the side of the camera to monitor its temperature while it is in the cold room A full description of the procedure given in Appendix I 28 Test results A formal test plan was written for the tests at Carleton and for the data acqui sition at Edmonton it is included as Appendix A Five tests were planned for the cam era The first two involved placing the camera in the cold room without any protec tion for a very short period of time The third test was used to determine the best way to protect the camera against the cold The fourth test checked if the camera s optics were affected by the cold Finally the last test
6. For example an x ray micro computed tomography scanner will re veal the internal features of the fragments as opposed to the surficial model created with the laser camera however the challenge would again be to use the scanner in the cold The creation of reference polished thin sections of the various lithologies found in this meteorite would help to link the geological properties with the physical 57 properties Finally it will be useful to investigate how the hydrophilic nature of the meteorite regardless of whether it is pristine or degraded affects the physical mea surements Presently this property of Tagish Lake limits comparisons between differ ent suites of data 58 7 References Beech M and Coulson I M 2010 The Tagish Lake meteorite microstructural porosity variations and implications for parent body identification abstract 708 GeoCanada 2010 Britt D T and Consolmagno G J 2003 Stony meteorite porosities and densities A review of the data through 2001 Meteoritics and Planetary Science 38 1161 1180 Brown P G Hildebrand A R and Zolensky M E 2002 Tagish Lake Meteoritics and Planetary Science 37 619 621 Brown P G Hildebrand A R Zolensky M E Grady M Clayton R N Mayeda T K Tagliaferri E Spalding R MacRae N D Hoffman E L Mittlefehldt D W Wacker J F Bird J A Campbell M D Carpenter R Gingerich H Glatiotis M Greiner E Mazur M J McCausl
7. al 2002 Porosity was not measured because of friability Density measured via sample the Archimedean beads method Error determined by comparing the density of a reference piece of quartz Entry model 37 58 Brown et al 2002 Based on orbital parameters a porosity for the entire body pre estimate breakup was calculated The lower part of the range was described as the more probable porosity Initial estimate 1 50 Brown et al 2000 Rough estimate from collected samples Beech and 4 5 15 4 Beech and Coulson 2010 Microporosity measured from SEM images results may suffer from Coulson the coastline paradox as porosity increased with magnification 10 2 Methods Definitions of bulk density and porosity The two physical parameters of the Tagish Lake meteorite that were measured in this study were bulk density and porosity A Konica Minolta Vivid 9i laser scanner was used to image fragments to create a representative three dimensional virtual model whose bulk volume was computed From the definition of bulk density p as ratio of mass M to volume V including all of the object s internal void space caused by pores or fractures the final result was simply Consolmagno and Britt 1998 McCausland et al 2011 peA 1 V The mass can be easily determined by weighing the sample on a three beam or electronic balance however the volume is by far more difficult to ac
8. containing over half a million dollars worth of geological samples is very much appreciated Beth Halfkenny lent me a suite of coal samples to use as analogues to Tagish Lake while I was experimenting in Ottawa Dr Phil McCausland at Western University provided valuable insight into the nature of the Tagish Lake meteorite Last but not least Chris Fry has shared his invaluable expertise with laser imaging and modeling since last year Table of contents Title page Faculty approval page Abstract Acknowledgements Table of contents List of tables List of figures 1 Introduction Research objectives Importance of bulk density and porosity Tagish Lake meteorite background 2 Methods Definitions of bulk density and porosity Measurement of density Measurement of porosity 3 Thermal stability Background Dewpoint Camera Design of protection against the cold Test results Conclusion and addendum 4 Results Error analysis 5 Discussion 6 Conclusions and future work 7 References Appendix A Test plans Part A Camera tests at Carleton vi ii iii iv vi viii ix N Ne me 10 11 16 19 19 19 23 24 28 34 37 40 45 35 58 6l 62 Preamble Equipment list Test 1 Unplugged cooling and warming test Test 2 Plugged in cooling and warming test Test 3 Covered cooling and warming test Test 4 PCA tests Test 5 Analogue tests Part B Scanning of meteorite samples at Edmonton Preamble Desc
9. ever a new limitation was conclusively identified by day 3 Occasional horizontal lines with no data present going through an otherwise good scan were noticed to oc cur well into a scanning session no earlier than 60 75 minutes from the start They were not noticed in Ottawa because there were not enough scans made with material results Furthermore scanning sessions did not run as long in Ottawa as in Edmonton first no such necessity existed and secondly the temperature of 15 C in Ottawa as compared to 10 C in Edmonton made a difference as to how long a scanning session could last The maximum session in Ottawa was approximately two hours it could be exceeded by 10 15 minutes on occasion in Edmonton the longest session was 2 5 hours before the scans quality became too unreliable It is important to note that two new blankets were added on day 3in Edmonton because the integrity of the older ones was in doubt however in this new configuration it seemed that the instrument would approach thermal equilibrium The cooling rate approached approximately 1 C per 45 minutes after an hour in the freezer which is insignificant when compared to the limitation imposed by the dataless lines The cause of these dataless lines stems from the limitations on the charge cou pled device CCD in the instrument which converts laser reflections into a digital format The CCD probably located behind the light receiving lens began to func tion
10. hoped that testing will start on the week starting on 10 June It is intended that week starting 24 June is left as spare time as the departure date to Edmonton is on 29 June A list of required equipment is given on the following page 1 Unplugged cooling and warming test 2 Scanning cooling and warming test 3 Covered cooling and warming test 4 PCA test 5 Analogue test These tests will be done in the order above Critical temperature the highest temperature out of the dewpoint temperature or the thermal range of the camera Thermal range The operating range of the Vivid 91 is 10 40 C with atmospheric water content corresponding to or less than a relative humidity of 65 at 20 C with no condensation The storage range is 0 40 C with atmospheric water content corresponding to or less than a relative humidity of 85 at 35 C with no condensation For all tests there are some steps that need to be done every time e Determination of dewpoint temperature outside the cold room by reading the temperature and relative humidity and converting those to dewpoint using the psychrometric chart 65 Appendix I Thermocouples must be taped such that there is no metal on metal contact which can cause noise in the readings At any hint of condensation on any part of the camera the test should be stopped and steps must be taken to ensure that it occurs on surfaces other than the camera e g the plastic bags The exa
11. involved scanning an analogue sample to see if the camera would scan well under the cold conditions In the first test the camera was placed unplugged into the cold room without any thermal protection The camera cooled very quickly and the test was stopped in a matter of seconds The second test was to be a repeat of the first but with the camera turned on It was not performed on the basis of the previous result The goal of the third test was to optimize the design of the protection to maxi mize the time that the camera could spend inside the cold room Ideally the camera should be able to spend up to two consecutive hours in the cold room at a time Based on one scan taking approximately 90 seconds a typical 60 scan library could be made in approximately 90 minutes The two hour limit is not only for the camera but also for the operator sitting in a cold room below 10 C for an extended time is dangerous The final design which allowed the camera to last for over two hours at 15 C without cooling below 10 C involved wrapping the camera with five protec tive layers First foam pads were placed on the camera s edges and over the lenses Then two layers of thermal blankets with holes cut for the two lenses were draped over the camera A lab coat was placed on the two thermal blankets and two more layers of thermal blankets with holes cut for the two lenses were draped over the lab 29 coat Finally the blankets and coat were wrapp
12. lation from the fitted plane should be ideally near the accuracy of the instrument as quoted by the manufacturer 0 05 mm As long as the standard deviation is low the model can be considered representative of the scanned object The results of the PCA tests are in figure 11 The reproducibility or precision of the bulk volumes of the model has been thoroughly investigated in previous studies e g McCausland et al 2011 Fry 2013 thesis On average the inter operator variability is 1 as such the uncertainty of the bulk volume measurements is considered to be at least 1 of the result Based on using these errors the resultant uncertainty on the bulk density measurements ranged from 0 017 to 0 019 g cm Alternatively the difficulty in assembling a model can be considered When two scans are meshed together they have a certain goodness of fit Some scans align better together which depends on the geometry of the target object 0 040 0 035 0 030 0 025 0 020 E Start i End 0 015 Standard deviation mm 0 010 0 005 0 000 2 July 2 3 July 1 3 July 2 4 July 1 4 July 2 5 July 1 5 July 2 Freezer session Figure 11 Standard deviation during the sessions in Edmonton PCA analysis was done regularly to ensure that camera was functioning well The number in brackets next to the date indicate the session number PCA tests were not done for the first session on July
13. length of I cm 48 Figure 15 Photograph of P 10a with similar orientation to that in F igure 14 The cube has an edge length of 1 cm The larger white surfaces are pieces of foil stuck to the fragment 49 Figure 16 Direct view of fusion crust in fragment P 10a Some of the crust in the lower right corner has broken off This view is rotated approximately 90 clockwise facing down from Figure 14 The cube has an edge length of 1 cm 50 ut oe Figure 17 Photograph of P 10a with similar orientation to that in Figure 16 The cube has an edge length of 1 cm white surfaces are pieces of foil stuck to the fragment 2S Ea The larger 51 Figure 18 Model of fragment P 4 cube has an edge length of 1 cm While it is almost entirely fusion crusted it displays an unusual bumpy and pitted texture The 52 53 Results from the scans and the photographic comparisons are shown in Fig ures 14 to 18 The camera was successfully used to create high fidelity 3D models of the 13 meteorite fragments The low albedo of the fragments did not pose a challenge when making the scans nor did the variety of fusion crusted and broken surfaces Figure 14 shows fragment P 10a where there is a transition between the broken sur face and fusion crust the validity of the representation is confirmed by Figure 15 A majority of the fragments imaged had a mostly complete fusion crust Figures 16 and 17 show another view of fragmen
14. of the reaction which would increase the grain density and thus the porosity Chemical degradation which likely involves both a loss of mass and volume can explain the difference between the literature and the observations Differences in technique may also explain the difference The degraded frag 46 ments measured by McCausland et al 2011 were done by laser imaging and those bulk densities are similar to what was obtained in this study In contrast the literature values shown in Figure 13 were all done by the Archimedean bead method with large 1 mm beads except the data point of 1 50 g cm 37 58 which was estimated from an orbital model for the parent body of the Tagish Lake meteorite Using such large beads risks obtaining low bulk density and high porosity because of systematic error The laser camera was shown to be an excellent tool for imaging and docu menting very fragile and unique material The samples are so mechanically weak that even using the Archimedean beads method would have likely caused significant dam age especially to the more dusty lithologies 60 50 40 Porosity 30 20 1 40 1 60 1 70 Bulk density g cm Measured values Literature values Figure 13 Comparison of the measured and literature values for bulk density and porosity 47 Figure 14 Model of fragment P 10a with broken surface facing and fusion crust on the right The cube has an edge
15. space An approximate closed solution for dewpoint as a function of initial temperature and relative humidity can be derived by combining the definitions of relative humidity and dewpoint Lawrence 2005 Alternatively the aforementioned closed solution may be shown graphically as a psychrometric chart Relative humidity RH is defined as the ratio of the initial partial vapour pres sure e to the saturated partial vapour pressure e for a constant temperature e RH 100 Xx aa 9 The distinction between saturated and unsaturated vapour pressure is a key factor to consider when designing the protection for the camera An air mass of a constant tem perature is limited to how much vapour it can hold if this temperature decreases the amount decreases as well The definition of dewpoint can be expressed in terms of partial vapour pres sures that are functions of temperature For an initial temperature T corresponding to the initial vapour pressure e and the final dewpoint temperature Ta eT j elT Ta e T i The Clausius Clapeyron equation is a first order differential equation dT R T oe where L is the enthalpy of vaporization 2 501 10 J kg at T 273 15 K and Ry is the gas constant for water vapour 461 5 J K kg It is assumed that the enthalpy of vaporization is effectively constant for the range between the initial temperature and the dewpoint A more accurate solution of the equation may be found by fac
16. three groups of files Polyworks files STL models and raw scans The Polyworks files are the models assembled from the raw scan data Each fragment has a dedicated Polyworks workspace Within this workspace are two groups of files Preliminary and Final The Final files have been cleaned up for various defects in the Preliminary versions There are four subclasses of files the original alignment project under IMAlign the original alignment with interscan overlap reduced under IMAlign and with a suffix OR the initial meshes under Polygon Models and with a prefix Mesh of and the final models under IMEdit and with a suffix model The STL models are the final models expressed as stl files corresponding to the Final model under IMEdit in Polyworks STL STereoLithography is a more universal 3D file format than the native Polyworks files and can be opened by most CAD and 3D visualization software The raw scans are present as a zip file It contains all of the raw ascii data as obtained by the laser camera Several cdk files are contained which can be imported into the Polygon Editing Tool used to control the laser camera and acquire the raw scans
17. to avoid condensation on exit ing the cold room is to isolate the lens area entirely from the warm air Design of protection against the cold The camera can be roughly subdivided into two groups of components optics and electronics Figure 5 The electronics are more sensitive a combination of con densation and extreme cold may damage them In contrast the mostly glass based op tics do not react strongly to cold This assumption was verified during testing The basic plan for the design involves wrapping thermal blankets around the camera These blankets typically made of a synthetic material and coated with metal resemble a very light and thin version of aluminium foil Also known as space blan kets they are used by runners after long distance races to prevent a dangerous de cline in body temperature The blankets work by reflecting radiating heat back to the wearer In the case of the camera the blankets will keep the heat of the camera within in the wrapping Foam pads were placed on the camera and used for two purposes first to prevent obstruction by the blankets of the laser emitting window and the light receiving lens and secondly to make it so that the blankets do not touch the camera as to create air pockets for insulation Holes were cut through the blanket for the laser emitting window and light receiving lens and were secured with elastic bands Finally type K chromel alumel thermocouples accuracy of 2 2
18. was measured via helium pycnometry Laser imaging has been previously successfully used to characterize a variety of stony and iron meteorites However due to the uniqueness and fragility of this meteorite both chemically and physically it is kept permanently in a freezer at temperatures never exceeding 10 C The laser camera used in this study the Konica Minolta Vivid 9i is not designed to be used at 10 C To protect it against the cold a method of wrapping it with thermal blankets was devised These measures allowed the camera to be operated for at least two hours in the cold consecutively after which it had to be taken outside the cold room to be warmed up Through this work it was shown that the laser camera could be adapted for use in an extreme environment which will allow it to be used in the future to characterize other frozen artifacts or geological materials The bulk density of the 13 measured Tagish Lake fragments mostly clustered around 1 80 g cm with some near 1 90 g cm possibly because of differences in lithology The measured porosity for 11 fragments was generally near 30 with some deviation accounted for by lithology or contamination Compared to previously published literature values which are mostly for degraded fragments the measured bulk density was higher and the porosity was lower As fragment degradation involves the loss of volatiles this result is not surprising However Tagish Lake is quite hydro
19. will be recorded When the critical temperature is reached the camera is removed from the cold room and the temperature time data is still recorded until the camera re equilibrates When the camera is removed for the cold room it will be unplugged because there is no need to run scans The laptop is placed first in the cold room and readied for scanning The laptop will be wrapped in a thermal blanket to keep it warm although the risk is not major because it is unlikely that test will run for a long time The camera is wrapped up and placed into the cold room with the attached thermocouples It is plugged in turned on and connected to the laptop At this point the usual scanning rhythm will begin Unlike in the two previous tests the camera will be wrapped and thus there must be an extra procedure for wrapping it Photographs will be present in Appendix II when the thermal procedure is finalized The camera must be removed from the tripod before wrapping it Foam pads 1 10 have been previously made parts 1 8 go on the camera corners parts 9 10 are for the lenses The parts are designed to fit in specific areas on the camera Parts 1 4 go on top parts 5 8 go on the bottom evens are on the non cable side odds are on the cable side parts 1 and 2 are the only interchangeable parts Part 9 goes on the laser lens part 10 goes on the receiver lens Foam pads 1 8 are secured in place with the tape where necessary and a l
20. Physical characterization of the frozen fragments of the Tagish Lake meteorite by Maxim Ralchenko A thesis submitted to the Faculty of Science in partial fulfillment of the requirements for the degree of Bachelor of Science Department of Earth Sciences Carleton University Ottawa Ontario August 2013 The undersigned recommend to the Faculty of Science acceptance of this thesis Physical characterization of the frozen fragments of the Tagish Lake meteorite submitted by Maxim Ralchenko in partial fulfillment of the requirements of the degree of Bachelor of Science iii Dr Claire Samson Thesis Supervisor Professor Department of Earth Sciences Carleton University Dr Richard Herd Thesis Supervisor Natural Resources Canada Adjunct Professor Department of Earth Sciences Carleton University Dr Sharon Carr Chair Department of Earth Sciences Carleton University Abstract The Tagish Lake meteorite is a C2 ungrouped carbonaceous chondrite with unique physical and chemical properties There are two groups of fragments pristine which are those recovered within days of the 18 January 2000 fall and degraded recovered a few months later in the spring The objective of this study was to non destructively characterize the physical properties of Tagish Lake specifically by measuring bulk density and porosity for a suite of pristine fragments The bulk density was measured via laser imaging and porosity
21. T 2011 Determination of bulk density for small meteorite fragments via visible light 3 D laser imaging Meteoritics and Planetary Science 46 1097 1109 60 McCausland P J A 2013 Personal communication Norton R O 2002 The Cambridge encyclopedia of meteorites Cambridge U K Cambridge University Press 354p Smith D L 2005 Nondestructive characterization of stony meteorites M Sc thesis Carleton University Ottawa Canada Smith D L Samson C Herd R K Deslauriers A Sink J E Christie I and Ernst R E 2006 Measuring the bulk density of meteorites nondestructively using three dimensional laser imaging Journal of Geophysical Research 111 E10002 Wilkison S L McCoy T J McCamant J E Robinson M S and Britt D T 2003 Porosity and density of ordinary chondrites Clues to the formation of friable and porous ordinary chondrites Meteoritics and Planetary Science 38 1533 1536 Zolensky M E Nakamura K Gounelle M Mikouchi T Kasama T Tachikawa O and Tonui E 2002 Mineralogy of Tagish Lake An ungrouped type 2 carbonaceous chondrite Meteoritics and Planetary Science 37 737 761 61 Appendix A Test plans Physical characterization of the frozen fragments of the Tagish Lake meteorite Part A Camera tests at Carleton Part B Scanning of meteorite samples at Edmonton Appendix I Psychrometric chart Appendix II Set up of thermal protection Appendix II Time temperature rec
22. a with similar orientation to that in Figure 16 Model of fragment P 4 with unusual surface visible ix 12 15 18 22 26 21 30 31 33 39 41 43 47 48 49 50 51 52 1 Introduction Research objectives The main objective of my research was to enrich the database of values for bulk density and porosity for pristine samples of the Tagish Lake meteorite held in the Meteorite Collection of the University of Alberta These physical parameters were to be analyzed in detail as they yield clues to the character of the processes that have formed and evolved the meteorite and its parent body Some fragments of the Tagish Lake meteorite are termed pristine because they are frozen Specifically it means that they were recovered within days after the fall 18 January 2000 and kept at a cold temperature since then between the fall and their arrival at the University of Alberta they were not allowed to warm up above 7 C The key characteristic that qualifies a sample as pristine or not is the presence of certain volatile organic compounds e g naphthalene if they are present the sample is pristine otherwise it has thawed Herd R K 2013 A helium pycnometer was used to determine porosity the instrument was brought to Edmonton by Dr Dan Britt of the University of Central Florida Bulk density was determined by 3D laser imaging and the Konica Minolta Vivid 91 3D digitizer used in that step was transported by me These 3D models are now
23. and P J A Plotkin H and Mazur T R 2000 The fall recovery orbit and composition of the Tagish Lake meteorite a new type of carbonaceous chondrite Science 290 320 325 Consolmagno G J and Britt D T 1998 The density and porosity of meteorites from the Vatican collection Meteoritics and Planetary Science 33 1231 1241 Consolmagno G J Britt D T and Macke R J 2008 The significance of meteorite density and porosity Chemie der Erde 68 1 29 Fry C Samson C McCausland P J A and Herd R K 2012 3D laser imaging of iron meteorites abstract 2703 Lunar and Planetary Science Conference XLIII Fry C Melanson D Samson C McCausland P J A Herd R K Ernst R K Umoh J and Holdworth D W 2013a Physical characterization of a suite of Buzzard Coulee H4 chondrite fragments Meteoritics and Planetary Science 48 1060 1073 Fry C Ralchenko M McLeod T Samson C McCausland P J A and Herd R K 2013b Non destructive density measurements of five iron meteorite suites abstract 5356 76th annual Meteoritical Society meeting Fry C Samson C Butler S McCausland P J A and Herd R K 2013c 3D laser imaging of tektites abstract 2597 Lunar and Planetary Science Conference XLIV Fry C 2013 3D laser imaging and modeling of iron meteorites and tektites M Sc thesis Carleton University Ottawa Canada Herd C D K Blinova A Simkus D N Huang Y Tarozo R Alexander
24. ared to this base line The camera is placed unplugged and uncovered into the cold room Depending on the amount of room that is available it is either mounted on the tripod or the field calibration rig The two thermocouples are taped to the sides of the camera The camera is allowed to cool to a few degrees above the critical temperature While it is cooling the temperature at regular time intervals is noted The interval will be initially 30s but will change if the thermal response of the camera is longer or shorter The test will start with an initial temperature outside the cold room The camera will be placed into the cold room and temperature time data will be recorded When the critical temperature is reached the camera is removed from the cold room and the temperature time data is still recorded until the camera re equilibrates No specialized set up other than placing the camera into the cold room with attached thermocouples is required Temperature time data will be recorded manually The data will be then entered into a spreadsheet and graphed As this test is first the worst case thermal response of the camera is not fully established The first iteration of this will involve cooling to 5 C above the critical temperature As the camera is unplugged the requisite thermal range is the larger storage range of the camera No scans are taken The expected temperature change and contrast will be larger than the optimal c
25. ct set up in terms of the laptop camera turn table and target will have to be improvised because the the availability of spaces and its configuration changes daily within the cold room Equipment list 66 Laser camera USB extension USB SCSI cable Power cord Extension cord Tripod Masking tape Wrenches screwdriver Thermocouple 3 Multimeter 2 Weather station Mouse and pad Measuring tape Sandpaper Thermal blankets 4 7 Laptop R for receving Power cord for laptop R Laptop A for analysis Power cord for laptop A HASP key 2 Binder clips or clothespins Photocamera charger adapter Turntable Elastic bands Calibration chart Lab coat Warm clothes Test plans Notebook Clipboard Scrap paper Watch or timer USB key for data transfer Ziploc bags 3 Paper towels Foam pads 1 12 spares Heat packs DVD blank lives 67 Test 1 Unplugged cooling and warming test Objective Methodology Set up Data analysis Risks Notes To determine the thermal response of the camera without any sources of heat or insulation This test will show the worst case scenario for the camera Ideally any further steps will have a smaller change in temperature for the same interval of time comp
26. curately determine in a truly non destructive way Working with the bulk density p porosity n may be determined by knowing the grain density p Porosity typically expressed as a percentage is defined as follows Brit and Consolmagno 2008 _ Pe Pg n l 2 A two chamber helium pycnometer is used to determine grain density knowing the volume of chamber A V4 and chamber B Vs along with the initial P and final pressures P the grain volume V is calculated as follows xV 83 11 Grain density is defined as the density of an object excluding all pore spaces following from equation 1 the grain density is simply the total mass divided by grain volume Pg M 7 4 Measurement of density The bulk density of the Tagish Lake fragments was determined via 3D laser imaging following the technique described by Fry et al 2012 2013abc McCausland et al 2011 and Smith et al 2006 The camera model used for this project is the Konica Minolta Vivid 9i It acquires scans of a resolution of 640 by 480 voxels a voxel is the 3D analogue of a 2D pixel A meteorite fragment is placed on a turntable Typically the Vivid 9i is used with a mechanical turntable that is also connected to the Polygon Editing Tool the program that receives the scans However to minimize the amount of electronics that was placed into the cold room a manual swivel base with a scale graduated in increments of 20 30
27. d to give V Jal 15 y b The uncertainty on bulk volume was discussed previously at length For the grain volume the standard deviation of the five last measurements made by the pycnometer is used E c Ss S gt a P 3 sg a 40 Bulk volume cm Figure 12 Standard deviation as a function of bulk volume 43 44 While the uncertainties on the final result hinge on a few assumptions not directly related to the performance of the instruments used to make measurements they are nonetheless reasonable and practical estimates The errors on the bulk volume are lower than would be the case with other methods but that is not unreasonable as laser imaging has been previously demonstrated to be an excellent method by which to determine bulk density e g Fry et al 2013abc McCausland et al 2011 Furthermore the other important non destructive method in use for meteorites the Archimedean bead method is sensitive to more uncontrollable factors than 3D laser imaging For example the bead behaviour suffers from changes in humidity and the result depends on how consistently the beads are poured In contrast 3D laser imaging depends on a good choice of scans and properly guiding the software in the model assembly step There is more room for consistency and hence reproducibility of results in 3D laser imaging than in the beads 45 5 Discussion It is apparent from Table 2 and Figure 10 t
28. e model is a high fidelity representation of the actual object its bulk volume is determined from which the bulk density can be calculated The main complication with this method is that watertight 3D models cannot be built if there are holes that cannot be filled As such it was necessary to be diligent and acquire a full 54 scan library per sample Nevertheless because of time constraints less scans were acquired on a few occasions but the preliminary models were assembled promptly after imaging to ensure that there were no gaps in the data Another complication from this method is the thermal stability of the laser camera which is discussed in detail in following sections There are several other methods of measuring the bulk volume of meteorites The Archimedean glass bead method was introduced by Britt and Consolmagno 1998 Using Archimedes principle to calculate the bulk volume of an object involves submerging it in water the volume of water displaced by the object is proportional to its volume This method was used until the early 20th century and before on meteorites however it is potentially destructive because the water can either react with the meteorite or infiltrate its pore spaces In the method introduced by Britt and Consolmagno 1998 glass beads with a diameter of 40 to 100 um act as the Archimedean fluid They are chemically inert and do not infiltrate pore spaces This method is fast and reliable but it cannot be
29. ed up and held with elastic bands and clothespins to make the enclosure of the camera reasonably airtight An example of a configuration is given in Figure 7 The time temperature data for the third test which involved five layers of protection is shown graphically in Figure 8 The last step in keeping the camera safe takes place when it is removed from the cold room By ne cessity the lenses must be exposed To avoid condensation the two exposed areas were covered with a plastic bag which was secured with an elastic band this way the warm air cannot contact the lens and cause condensation 30 Figure 7 The camera has been wrapped in five layers four thermal blankets and a lab coat and mounted on the tripod 1 A sample of the Allende meteorite used as an analogue is on the turntable 3 The camera is connected to a receiving computer 2 and the thermocouple multimeter setup 4 In Edmonton a five layer configuration was used at first Later two more thermal blankets were added because of concerns that the first four blankets lost quality through use 35 25 20 In y 0 00714121x 3 18373 R 0 962465 15 Temperature C 10 0 20 40 60 80 100 120 Time min Figure 8 Camera temperature versus time for the third test five layer setup for a cold room temperature of 15 C This experimental data measured by thermocouples on the sides of the camera has been fitted with a negative exponential curve
30. eet and graphed The ability to predict the thermal behavior of the camera is important and the optimal data set may be used to predict how long it will take to reach various critical temperatures the dewpoint is not constant The worst case scenarios are now known if the camera is turned on or off Ideally any tests within those time limits should be safe A new concern now arises for the camera by necessity the lenses must be exposed to the cold air whereas the rest of the camera should stay relatively warm if the design is proper Hence the lenses will spend enough time in the cold room to possibly equilibrate to the cold This will present a challenge when exiting the cold room as condensation will occur on them The solution to this problem is to place a plastic bag over the lens when the scanning is done The condensation that would otherwise occur on the lens is because the lens cools the surrounding warm humid air to its dewpoint If the lens is isolated from the warm air the cold air around it and within the plastic bag will warm up However because it was dry when it was cold it cannot be wet when it warms up Furthermore any condensation from the warm air will be on the exterior surface which is the plastic bag For this reason the camera should not be cooled below its dewpoint as there could be complications upon exiting it is not as practical to wrap it in a big plastic bag When the camera is removed from the cold
31. erve meteorite sample and note geometry Determine Angular increment Orientaiton A Orientation B Orientation C Extras Set up laptop in cold room Wrap laptop in spare thermal blanket Plug in camera and connect to laptop Photograph set up as necessary Do PCA scans as necessary Test scan meteorite Verify position focus intensity settings for the orientation Complete meteorite scan for the orientation Save scans as a one cdk per orientation Repeat above for different orientations Isolate lenses and thermocouple contacts from air with plastic bag Remove from cold room let re equilibrate Appendix I Dewpoint C 10 Psychrometric chart 20 Air temperature C 30 40 81 82 Appendix II Set up of thermal procedure for tests A 3 5 all tests B Pe meomrnnn 12 13 14 15 16 17 18 Remove camera from box and verify that the switch is ON Add lower foam pads 5 8 and secure with elastic band Add upper foam pads 1 4 and secure with elastic band Attach the thermocouple probes to camera yellow wire is on cable side brown wire is on non cable side Attach lens pads Secure lower pad with masking tape Optional place heating pads in areas that leak heat Plug in SCSI cable and power cable Bring the four wires near each other Place two cut thermal blankets over the camera and push the loose ends unde
32. excellent archives of the pristine fragments Destructive sampling is eventually unavoidable for a portion of the fragments due to the unique organic chemistry of the meteorite Finally a major part of the project became to design a way by which the laser camera could operate in the cold room in which the meteorite is studied The electronics are of commercial grade and are not reliable below 10 C whereas the cold room in which the work took place was at 10 C 1 Also referred to as simply digitizer laser camera or camera Importance of bulk density and porosity Bulk density and porosity are intrinsic physical properties that provide insight into the processes that have formed and evolved a meteorite and its parent body Britt and Consolmagno 2003 Consolmagno and Britt 1998 Consolmagno et al 2008 Bulk density can be used to help classify meteorites and is required in the determination of porosity Questions that are posed in regards to porosity often centre around its cause What causes some meteorites to lithify and compact more than others Carbonaceous chondrites the category into which the Tagish Lake meteorite is classified have a characteristically high porosity of over 20 This observation suggests that this category of meteorites formed under physical processes that are much different than for other meteorites Tagish Lake being very friable and fragile is an extreme case Density and porosity must be c
33. hat the porosity of the fragments has clustered between 25 and 35 Within this range most of the densities cluster be tween 1 75 and 1 85 g cm with the exception of the large P 1 which had a low den sity and three samples with bulk densities near 1 90 g cm P 3a P 5a P 9a of which two P 3a P 5a have been described as having a darker interior The results are substantially different in bulk density and porosity from all of the literature values see Table 1 except for the three degraded fragments PM05 PM05a PM05c measured by McCausland et al 2011 The results for which both porosity and bulk density are available are given in Figure 13 Compared to the mea sured values the literature gives higher porosity and lower bulk density The differ ence can be interpreted as due to a loss of volatiles especially water ice in the de graded samples as compared to the pristine ones Furthermore contact with water could have caused it to dissolve or dislodge microscopic particles within the mete orite if the meteorite is very permeable then water would have removed these parti cles from within leaving behind more pore space Chemically the water would have induced terrestrial reactions with the mineral species which did not conserve internal mass through loss to the environment In that case the bulk volume would remain constant but bulk density would decrease Or the volume of the constituent phases decreased as a result
34. hermal blanket Plug in camera and connect to laptop Photograph set up Scan calibration chart repeated at a time interval proportional to how long camera can stay in the cold room Save scans as PCA _test4_ lt date gt _ lt iteration gt lt scan gt asc Record temperature time data Do not go below ne Isolate lenses from air with plastic bag Remove from cold room let re equilibrate 77 Test 5 Analogue tests Objective Methodology Set up Data analysis Risks Notes To attempt to image in a cold room a sample analogous to the Tagish Lake carbonaceous chondrite The camera will be protected using the optimal design per test 3 and appendix II The analogue sample will be scanned as it usually scanned in the downstairs lab If it one continuous scanning session is not possible several will have to be completed or the angular increment will be increased The camera is wrapped as per test 3 and appendix II It is placed in the cold room plugged in and attached to the laptop After the scanning is complete is it removed from the cold room per the procedures in test 3 and appendix II The gathered scans will be saved as vvd and asc files The asc point clouds will be assembled in PolyWorks as would be done under standard conditions Same as test 3 Temperature time data will not recorded only temperature will observed as to not remain in cold room too lo
35. ies and fragments the mere act of handling the meteorite during imaging left dust to sand sized bits of material on the turntable surface There are trends within the suite in organic matter and isotope abundances that describe the degree of aqueous alteration Herd et al 201 1a These trends can be extrapolated to characterize interstellar nebular and parent body processes Herd C D K 2013a Carbonaceous chondrites are the most chemically unfractionated group of meteorites and are particularly rare as they constitute around 5 of the meteorites known Traditionally carbonaceous chondrites are a group of meteorites having peculiar characteristics such high friability generally low density and little to no free nickel iron Mason 1962 The modern definition given by the Meteoritical Society is based on their chemistry the oxygen isotope compositions plot below the terrestrial fractionation line and most of the carbonaceous chondrites have Mg Si ratios near the solar value They are then further classified by petrologic type and group Tagish Lake was described by Hildebrand et al 2006 as one the most primitive meteorites known It is ungrouped but it has affinities to both the CI and CM groups Consolmagno et al 2008 in their report documenting the fall of the meteorite Brown et al 2000 described it as an intermediate specimen between the CM and CI groups The main affinities to the CM group are the presence of chond
36. ks and raw pycnometry data are in Appendix B Table 2 Bulk density and porosity of 13 pristine Tagish Lake fragments 38 Fragment Mass Bulk density Bulk density error Porosity Porosity error g g cm g cm P 1 157 760 1 72 0 02 P 10a 110 860 1 79 0 03 P 4 59 957 1 81 0 04 38 2 P 7 44 910 1 81 0 03 33 1 P 6 33 548 1 81 0 02 28 1 P 10b 24 889 1 79 0 02 30 1 P 9b 20 778 1 80 0 02 28 1 P 9a 18 314 1 87 0 02 28 1 P 11b 12 520 1 75 0 03 28 1 P 3a 11 471 1 89 0 02 28 1 P 5a 9 450 1 87 0 03 24 1 P 11r 8 892 1 75 0 03 30 1 P 11c 8 340 1 823 0 021 29 1 3 A 80 1 Density g cm Figure 10 Porosity as a function of bulk density for a suite of 11 Tagish Lake samples 39 40 Error analysis The uncertainty in the measurements was summed by quadrature also known as propagation by partial derivatives For bulk density the uncertainty on mass and bulk volume needed to be considered per equation 1 The mass of the meteorites was measured to three decimal places with an electronic balance the uncertainty on this measurement is 0 002g Quantifying uncertainty on the bulk volume is a more diffi cult question because of the model assembly process The process of fitting a plane to a 3D point cloud of a flat calibration object gives some measure of accuracy the standard deviation for 99 7 of the point popu
37. law The first few results are typically invalid as the instrument is still adjusting The final result delivered as grain volume is the average of the five last runs The set up of this apparatus is shown in Figure 3 Before the instrument is used for any measurements of a meteorite it must be calibrated with a reference object of known volume This technique does not require as much involvement from the operator as laser imaging A sample has simply to be put into its holder which is then placed into the sample chamber in the pycnometer It is then set to do its runs and the operator can wait outside the cold room for them to complete Unlike the laser camera the pycnometer equilibrated without problem to 10 C The pycnometer is not a black box instrument like the camera as it can be disassembled and inspected Finally the type of measurements made by the pycnometer were such that there was less risk of instrument problems due to the cold temperature compared to the laser camera 1 5 2 3 6 4 Figure 3 Setup of pycnometry apparatus 1 Helium gas tank 2 Ultrapyc 1200e pycnometer 3 Calibration object 4 Balance 5 Sample chamber 6 Reference chamber 18 19 3 Thermal stability Background The instrument used for the determination of the bulk density of the samples was the Konica Minolta Vivid 9i laser scanner It has an operating range of 10 40 C Konica Minolta manual but the meteorites are frozen and canno
38. mize the time that camera could spend in the cold room The cooling down of the camera cannot be delayed indefinitely given the re sources available so the best option was to use it in increments of a few hours When the camera cooled to a critical temperature defined as the maximum of either the dewpoint or the bottom of the operating range it had to be taken outside the cold room to warm up Risk to the camera is present at two times when the camera enters the cold room and starts to cool down and when it leaves the cold room to warm up If warm air within the camera does not circulate out then it cools and its absolute water con tent remains constant When this air body within the camera reaches its dewpoint which is equal to that outside the cold room condensation occurs As circulation be comes restricted in the camera so it does not cool quickly the implication is that the camera cannot be allowed to reach the dewpoint of the room in which the camera was prepared When the camera is removed from the cold room the risk of warm air con densing on a cold surface arises If there is some condensation on the material with 24 which the camera is wrapped it is not necessarily problematic as long as this conden sation occurs on the external surface of the cover However by necessity the laser and receiver lenses must be exposed thereby forcing them to equilibrate to cold room s temperature of around 10 C The simple way
39. ned with bulk volume to yield porosity was 56 measured with a helium pycnometer This instrument did not need to be protected against the cold because of its different specifications and function During this study thirteen measurements of bulk density and eleven measure ments of porosity were made The discrepancy in the amount of measurements is a re sults of the two largest fragments not fitting into the pycnometer Most of fragments measured had a bulk density near 1 80 g cm and a porosity of 30 Three fragments clustered away from the main group at a bulk density closer to 1 90 g cm which may represent a different lithology The largest fragment had a bulk density of 1 72 g cm which is significantly lower than the rest Finally another sample also stood out from the main group with a higher than average porosity of 38 this different porosity has been tentatively accounted for by contamination Based on previous studies that have employed this laser camera an attempt was made to propagate the uncertainty for single measurements The challenge is to determine the error on the bulk volume A minimum uncertainty in bulk volume was chosen based on previous inter operator variability studies and the contribution of the geometry of a fragment The net result was an uncertainty of 0 02 0 04 g cm for bulk density and 1 2 for porosity Future work should continue the non destructive characterization of this unique meteorite
40. ng The gathered scans for this test should be saved for data analysis A consistent filename format will be helpful lt sample name gt _ lt date gt _testS lt scan gt vvdlasc Critical steps 78 Description Initials and date Note Outside temperature C Outside humidity Inside temperature C Calculate Dewpoint gt C Attach foam pads to camera Attach thermocouples to camera Wrap with thermal blanket Add extra layers optional Set up timer Set up analogue sample Set up laptop in cold room Wrap laptop in spare thermal blanket Plug in camera and connect to laptop Photograph set up Scan analogue sample Angular interval Save scans as lt sample name gt lt date gt _test5_ lt scan gt vvdlasc Do not go below C Isolate lenses from air with plastic bag Remove from cold room let re equilibrate 79 Part B Scanning of meteorite samples at Edmonton Preamble This procedure combines parts of test 3 4 and 5 from Part A The procedure describes the usual steps taken to scan a meteorite sample with modifications to account for the cold room conditions Description Objective Methodology Set up Data analysis Risks Notes To image samples of the frozen Tagish Lake meteorite The camera will be protected using the optimal design as described in appendix II The typical scanning se
41. ng much more calcite less magnetite and little to no CAIs Zolensky et al 2002 However it was later understood to be much more heterogeneous that previously thought later workers have expanded upon the two zones suggesting a CAI poor magnetite sulfide lithology and a carbonate rich lithology dominated by siderite Izawa et al 2010b There is an overall paucity of data on the bulk density and porosity of Tagish Lake Four previous studies have yielded directly measured values see Table 1 but the distinction between pristine and degraded samples was not always clear Zolensky et al 2002 Hildebrand et al 2006 Beech and Coulson 2010 and McCausland et al 2011 Little work has been done with the pristine fragments as they are kept in cold storage hence access to them is rigidly controlled In addition to the direct measurements two studies have estimated the bulk density and porosity of Tagish Lake based on its flight and breakup characteristics Brown et al 2000 Brown et al 2002 Table 1 Density and porosity values for Tagish Lake from previous studies Fragment Bulk density Error Porosity Error Source Notes g cm g cm PM05a 1 86 0 03 McCausland et al 2011 Degraded Measured via laser imaging PMO05 1 73 0 06 McCausland et al 2011 Degraded Measured via laser imaging A large crack was present in the sample macroporosity may have decrea
42. nnual Meteoritical Society meeting Hiroi T Zolensky M E and Pieters C M 2001 The Tagish Lake meteorite A possible sample from a D type asteroid Science 293 2234 2236 Izawa M R M Flemming R L King P L Peterson R C and McCausland P J A 2010 Mineralogical and spectroscopic investigation of the Tagish Lake carbonaceous chondrite by x ray diffraction and infrared reflectance spectroscopy Meteoritics and Planetary Science 45 675 698 Izawa M R M Flemming R L McCausland P J A Southam G Moser D E and Barker I R 2010 Multi technique investigation reveals new mineral chemical and textural heterogeneity in the Tagish Lake C2 chondrite Planetary and Space Science 58 1347 1364 Konica Minolta 2007 Vivid 91 documentation Lawrence M G 2005 The Relationship between Relative Humidity and the Dewpoint Temperature in Moist Air A Simple Conversion and Applications Bulletin of the American Meteorological Society 86 225 233 Macke R J Britt D T and Consolmagno G J 2011 Density porosity and magnetic susceptibility of carbonaceous chondrites Meteoritics and Planetary Science 46 1842 1862 Mah J Samson C McKinnon S D and Thibodeau D 2013 3D laser imaging for surface roughness analysis International Journal of Rock Mechanics and Mining Sciences 58 111 117 Mason B 1962 Meteorites New York John Wiley and Sons Inc 274p McCausland P J A Samson C and McLeod
43. on Initials and date Note Outside temperature C Outside humidity Inside temperature C Calculate Dewpoint C Attach thermocouples to camera Set up timer Set up laptop in cold room Wrap laptop in spare thermal blanket Plug in camera and connect to laptop Run standard scanning rhythm Photograph test set up Record temperature time data Do not go below C remove from cold room Record temperature time data until equilibration 71 Test 3 Covered cooling and warming test Objective Methodology Set up Wrapping set up To maximize the amount of time that can be spent by the camera in the cold room at one time by optimizing the insulation design The camera is wrapped up before it is placed in the cold room A temperature reading is taken Depending on the amount of room that is available it is either mounted on the tripod or the field calibration rig The two thermocouples are taped to the sides of the camera The camera is turned on and a normal continuous scanning rhythm is run The camera is allowed to cool to a few degrees above the critical temperature While it is cooling the temperature at regular time intervals is noted The time interval chosen will be based on the results of tests 1 and 2 The test will start with an initial temperature outside the cold room The camera will be placed into the cold room and temperature time data
44. on on provenance and the nature of pre solar materials Herd and Herd 2007 Tagish Lake is chemically distinct from CM or CI carbonaceous chondrites as it has experienced little to no metamorphism Brown et al 2002 although it has undergone extensive yet incomplete aqueous alteration based on the excellent evidence of secondary mineralization Zolensky et al 2002 The texture of the minerals is such that the relative timing of alteration may be determined The mineralogy of Tagish Lake is dominated by abundant phyllosilicates especially saponite and serpentine group minerals It is a breccia at all scales Zolensky et al 2002 succinctly it is a breccia composed of breccia The matrix is opaque and consists of phyllosilicates sulfides and magnetite Tagish Lake has has up to 5 6 wt carbon Hildebrand et al 2006 making it one of the richest carbonaceous chondrites in carbon Herd C D K 2013a although its dark colouration is the result of abundant magnetite and sulfides Herd R K 2013 Within the matrix are extensively altered chondrules calctum aluminium inclusions CAIs iron magnesium calcium manganese carbonate minerals olivine pyroxene more phyllosilicates e g saponite iron nickel sulfides and minor native iron nickel alloy Izawa et al 2010a Izawa et al 2010b Zolensky et al 2002 The meteorite was initially subdivided into carbonate rich and carbonate poor zones with carbonate rich zones havi
45. onditions of test 3 care has be taken to inspect visually to check for condensation Critical steps 68 Description Initials and date Note Outside temperature C Outside humidity Inside temperature C Calculate Dewpoint EC Attach thermocouples to camera Set up timer Photograph test set up Record temperature time data Do not go below C remove from cold room Record temperature time data until equilibration 69 Test 2 Plugged in cooling and warming test Objective Methodology Set up Data analysis Risks Notes To determine the thermal response of the camera as its electronics are running and generating heat Ideally the camera will be able to last slightly longer than during test 1 The test will show how its electronics contribute to its overall temperature The camera is placed uncovered into the cold room and plugged in Depending on the amount of room that is available it is either mounted on the tripod or the field calibration rig The two thermocouples are taped to the sides of the camera The camera is attached to the receiver laptop The camera is turned on and a normal continuous scanning rhythm is run manually The camera is allowed to cool to a few degrees above the critical temperature While it is cooling the temperature at regular time intervals is noted The time interval chosen will based on the results of test 1 The te
46. ong elastic band or string one on top one on the bottom Part 9 can be optionally secured with tape part 10 needs no tape or string All necessary cables and thermocouples are attached The thermal blanket is placed over the pads so that the holes for the Data analysis Risks 72 lens are properly aligned The pads create some spacing between the blanket and the camera the layer of air helps insulate it The blanket is sealed around parts 9 and 10 with elastic bands The blanket is wrapped over the camera the ends of the blanket will converge at the bottom where the camera is attached to the tripod The blanket can be attached to the support with an elastic band or this can be done by attaching it to the tripod with the blanket in between Any gaps in the blanket are wrapped up and secured with clothespins The camera is placed on the appropriate mount i e tripod or field calibration unit plugged in and turned on The camera can be turned on when wrapped in the blanket If one blanket is insufficient to properly insulate the camera more layers can be add e g lab coat winter coat extra thermal blanket etc There will likely be changes to how exactly the camera is wrapped up as the goal of the test is to optimize the design The final result will be added to Appendix II to be used during Part A tests 4 5 and Part B all tests Temperature time data will be recorded manually The data will be then entered into a spreadsh
47. onsidered at all possible scales from micrometeorites to the parent body It is also a useful exercise to relate these physical properties of meteorites to their parent body asteroids however meteorites may not necessarily be representative samples as they are either strong material that has survived passage through Earth s atmosphere or weak material that was weak enough to have been ejected from its parent Consolmagno et al 2008 Finally as will be most applicable during this study trends in bulk density and porosity for a meteorite with several fragments this is the case with Tagish Lake are considered as well On a first order basis the trends tell us if the meteorite is homogeneous or heterogeneous Tagish Lake meteorite background The Tagish Lake meteorite is an ungrouped type 2 carbonaceous chondrite with unique physical and chemical properties The meteorite which fell on Tagish Lake in northern British Columbia near the border with the Yukon on January 18 2000 has not yet been extensively characterized with regards to its physical properties The circumstances regarding this fall are particularly fortuitous The Tagish Lake meteorite hereafter to referred to as Tagish Lake is very friable and overall mechanically weak The meteorite is one of a kind as stated by Brown et al 2002 Tagish Lake does not seem to fit into our existing meteorite taxonomy having characteristics that set it apart from any
48. or in contact with water The instability of the meteorite is evident it turns into mud when in contact with water and emits a sulfurous smell The dust cloud which formed when the meteorite broke up in the atmosphere also had an odor associated with it described variously as foul metallic sulfurous or chemical Hildebrand et al 2006 The original mass was in excess of 60 metric tonnes and it entered the atmosphere at a low entry angle and velocity entry angle of 14 5 1 6 at azimuth 330 7 2 4 traveling at 15 8 0 6 km s the combination of these circumstances allowed for some fragments to survive Hildebrand et al 2006 The question of whether the recovered material is representative of the whole mass or only the stronger fragments of a heterogeneous body was brought up by Hildebrand et al 2006 The conclusion that was made by the authors is that because a range of grain densities were measured 2 56 2 91 g cm the fragments constitute representative sampling of the whole body Hildebrand et al 2006 The fragility and chemical instability of the meteorite requires that it be stored in a freezer usually set to 20 C which incidentally makes it a prime example of cold curation as could be needed for samples returned from future Solar System missions Herd et al 2011b Hilts et al 2012 Mechanically Tagish Lake is extremely weak while there is a range of weaker and aqueously altered or dusty to stronger litholog
49. ording sheet This appendix is a copy of the formal test plans that were written for the testing sessions at Carleton and the imaging of Tagish Lake at Edmonton 62 Part A Camera tests at Carleton Preamble Before leaving with the camera to image meteorites in the cold room at Edmonton several tests will be done in Ottawa to verify that the camera will be thermally stable i e be able to operate in the cold conditions The temperature of the cold rooms in Ottawa and Edmonton will be 10 C The camera can be subdivided into two parts optical components in the front and the electrical components in the back The optical components are mostly glass hence they are of a lower risk than the electrical components which are typically the limiting factor for thermal range for most commercial instruments and appliances The main concern with the optics is that by necessity they have to be exposed to the cold Thus when the camera is removed from the cold room it is important to make sure that the lenses do not fog up A common technique used in ordinary photography is to put the camera in a plastic resealable bag Any condensation that does happen occurs on the bag instead of the lens A variant of this technique will be used when the camera is removed According to the documentation provided with the camera the safe operating range for the Vivid 91 is 10 40 C whereas the storage range is extended to 0 40 C The main goal of all
50. ore study of this specific sample is needed to give a definitive conclu sion Zolensky et al 2002 note that fragment P 4 was contaminated by RCMP dog nasal fluids a story that was confirmed by C D K Herd however the contamination does not explain the unusual porosity A final complication in the determination of bulk density is the very hy drophilic nature of the meteorite which has implications in comparing pristine and degraded samples The variation in mass caused by the absorption of water has been noted to be in the range of 0 1 1 g for the 50 gram thawed pristine fragment P 2 lo cated at the Royal Ontario Museum McCausland 2013 The adsorption of water in creases bulk density and decreases porosity The thirteen fragments measured in this study were all reweighed and their mass was stable at three decimal places The sam ples were all handled in the very dry environment of the cold room Therefore the hy drophilic nature of the meteorite should not affect the comparisons within the suite of new measurements made during this study but it must be considered when comparing with other datasets 53 6 Conclusions and future work Tagish Lake is a unique object possibly representing material with properties in between those of a comet and an asteroid Due to its very fragile nature it was im perative to characterize it in a non destructive fashion During this study two physical parameters bulk density and poro
51. other meteorite This uniqueness of the meteorite is at least partially an artifact of it being unstable at the Earth s surface The meteorite was recovered in two expeditions The first fragments recovered within several days after the fall are termed pristine as they not have been thawed Hildebrand et al 2006 There was originally under 900 g of pristine material available prior to destructive sampling When the material was acquired by the University of Alberta led consortium approximately 200 g was given to the Royal Ontario Museum and approximately 650 g to the University of Alberta Meteorite Collection Prior to the acquisition over 40 g of material was consumed for e g organic studies on the 10 39 g fragment 8a chipping off parts of fragments 1 and 2 and the creation of thin sections Herd R K 2013 Approximately 26 g of material has been consumed in organic studies after the acquisition Herd C D K 2013b Herd et al 2011a Overall about 620 g of pristine material remains at the University of Alberta These pristine samples were collected by local resident Jim Brook who took care to avoid touching the fragments with his bare hands Shortly after the fall of Tagish Lake a large snowstorm interrupted further recovery efforts and a second expedition was mounted a few months later in the spring late April to early May to recover more fragments These samples are termed degraded as they have either been warmed up
52. philic which may complicate the comparison between different suites of data This study was part of a systematic analysis of the meteorite and this bulk density and porosity data will be integrated with other studies in the future iv Acknowledgements I first thank my co supervisors Dr Claire Samson and Dr Richard Herd for all of their guidance and advice during this project Dr Dan Britt of the University of Central Florida provided financial support traveled with and operated his helium pycnometer in Edmonton and gave insight into the interpretation of the data Dr Christopher Herd of the University of Alberta welcomed me and Dr Britt into his lab to access samples and was an immense source of knowledge about the meteorite Dr Jason Mah laid the groundwork for the thermal protection of the camera Po Kong Lai lent his laptop capable of receiving data from the laser camera for use during the tests in Ottawa and for the trip to Edmonton Penka Matanska and Mike Antunes of the Department of Physics lent thermocouples and multimeters for use with the laser camera and gave excellent advice which greatly improved the design of the thermal protection Dr Tim Patterson and his lab members gave me access to their cold room so that I could test the camera in the cold prior to going to Edmonton Their patience with me over several weeks as I occupied a considerable portion of their lab space and sat in the cold room
53. r the camera Place labcoat over camera tie its arms between the lens pass wires through the hole in its side push the loose ends under the camera Place two cut thermal blankets over the camera and push the loose ends under the camera Secure as many of the loose ends as possible to the tripod connector at the bottom with an elastic band Ensure that the blankets and coat are tightly wrapped around the cables use an elastic band to secure the area if necessary Wrap the rest of the thermal blanket up and secure with clothespins or binder clips to make sure that the set up is reasonably air tight Bring the camera in the cold room and attach to tripod Ensure that nothing has shifted from the initial set up When camera reaches critical temperature safety margin isolate lenses and thermocouple contacts with plastic bag and remove from cold room and allow to re equilibrate eS Ss Photo 1 Up to step 3 corner pads attached and secured 83 Photo 2 Up to step 6 thermocouples and lens pads attached and secured Photo 3 Up to step 10 two cut thermal blankets wrapped Photo 4 Up to step 11 lab coat placed over two cut thermal blankets wrapped 84 Photo 5 Up to step 15 camera fully Photo 6 Up to step 18 camera wrapped and secured with clothespins removed from tripod lenses isolated f Photo 7 Up to step 16 camera set up L wi
54. rary of scans and then a few hours to process and assemble the model The apparatus is not easily portable as the laser camera is expensive heavy and fragile Assembly of the models requires significant operator judgment and there is some inter operator variability when measuring a fragment The model assembly process is the principal source of uncertainty in the final result A photograph of the experimental set up used is in Figure 2 15 Figure 2 Set up in cold room for laser imaging 1 Laser camera 2 Pycnometer 3 Balance 4 Flat calibration object 5 Tagish Lake fragment 6 Manual turntable 7 Receiving laptop 8 Thermocouple wire and multimeter 16 Measurement of porosity Porosity is measured using a helium pycnometer as described by Consolmagno and Britt 1998 Britt and Consolmagno 2003 Wilkinson et al 2003 Consolmagno et al 2008 and Macke et al 2011 A two chambered pycnometer was used The two chambers one for the sample and one for reference are connected with a valve A sample is placed inside one chamber The valve is closed off and helium is introduced into the sample chamber Helium is used because of its tiny atomic radius which allows it to quickly penetrate fractures in the samples Nevertheless a sample may be not fully permeable to helium which will give a greater grain volume Furthermore helium is chemically inert The pressure in the sample chamber is raised usually to approximatel
55. re Analysis of the scans and assembly of the models showed that there was no obvious change in quality between scans taken in the cold room and scans taken at room temperature The analogue samples used in the cold room were low grade lig nite and bituminous coals They were chosen because they most resemble the usual description of the Tagish Lake meteorite as a charcoal briquette The drawback to us ing coal was its very complicated geometry caused by intersecting fracture planes and 33 0 040 0 035 E 2 2 Z 0 030 ne z i a A a 0 025 0 020 10 15 20 25 30 Temperature C Figure 9 Standard deviation of a 3D point cloud from a plane fitted by PCA versus time A flat calibration object was scanned and the data was exported as an ASCII file for analysis with MATLAB 34 a lack of fusion crust While the surface texture per se is representative of the Tagish Lake meteorite the geometry most certainly is not and makes these analogue scans not very representative Nevertheless it was possible to assemble a model from the scans taken although its quality was poor due to the difficult geometry A defining feature of the pristine Tagish Lake samples and common to many meteorites is the presence of a smooth fusion crust To this end two samples of the Allende CV3 carbonaceous chondrite were borrowed from the National Meteorite Collection of Canada for imaging however the loan was conditional upon not free
56. ription Appendix I Appendix II Appendix II Appendix B Raw data outputs Appendix C Raw scan and model data 62 66 67 69 71 75 77 79 79 79 81 82 85 86 87 List of tables Table 1 Density and porosity values for Tagish Lake from previous studies Table 2 Bulk density and porosity of 13 pristine Tagish Lake fragments viii 38 List of figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Photograph of manual turntable used to orient meteorite samples Photograph of cold room set up for laser imaging Photograph of pycnometry set up Psychometric chart used to calculate dewpoint Annotated diagram of laser camera Photograph of preparation of camera for the cold room Photograph of the working design for thermal protection of the camera Graph of camera temperature with time during a cold room test Graph of test results for optical stability with time Graph of porosity and bulk density for Tagish Lake fragments Graph of test results for optical stability at Edmonton Graph of model standard deviation as a function of bulk volume Graph comparing literature and measured values Figure 14 Model of fragment P 10a with broken surface centred Figure 15 Figure 16 Figure 17 Figure 18 Photograph of P 10a with similar orientation to that in Figure 14 Model of fragment P 10a with fusion crust centred Photograph of P 10
57. room the insulating material will be kept on it to avoid condensation on the camera and so that it can warm up gradually Notes after the time in the cold room The gathered scans for this test are immaterial There will likely be several iterations of this test 73 Critical steps 74 Description Initials and date Note Test run number Outside temperature C Outside humidity Inside temperature C Calculate Dewpoint C Attach foam pads to camera Attach thermocouples to camera Wrap with thermal blanket Add extra layers optional Set up timer Set up laptop in cold room Wrap laptop in spare thermal blanket Plug in camera and connect to laptop Photograph test set up Run standard scanning rhythm Record temperature time data Do not go below C Isolate lenses from air with plastic bag Remove from cold room let re equilibrate 75 Test 4 PCA tests Objective Methodology Set up Data analysis Risks Notes To determine how the optics of the camera behave with time spent in the cold room and as the temperature of the camera changes The camera will be protected using the optimal design per test 3 and appendix II A flat calibration chart will be scanned at regular time intervals The scans will then be analyzed a posteriori The time and corresponding temperature will be recorded during the te
58. rules altered calctum aluminium inclusions CAIs and the presence of individual olivine grains It is also has affinity to the CI group based on the bulk chemistry abundant magnetite high carbon content and extreme friability However the composition of the carbonate minerals in Tagish Lake were distinct from what had been previously observed in either the CI or CM groups Norton 2002 As Tagish Lake is sufficiently distinguishable from other meteorite groups it has been classified as ungrouped Zolensky et al 2002 classified Tagish Lake as a type II carbonaceous chondrite and suggested a possible affinity to the CR group based on the texture and abundance of two of its constituent minerals siderite and magnetite According to the Meteoritical Society the diagnostic features of a type II carbonaceous chondrite include the presence of abundant fine grained matrix and hydrated minerals The sulfides contain nickel Finally chondrules are still present unlike in type I chondrites The parent body of Tagish Lake was most likely a D type asteroid based on orbital parameters and spectral data Hildebrand et al 2006 Hiroi et al 2001 Its parent body has also been described as an Apollo type asteroid based on its orbital characteristics Brown et al 2000 and as an intermediate between an asteroid and a comet Hildebrand et al 2006 As one of the most primitive objects known it is hoped that Tagish Lake could yield informati
59. sed bulk density PM05c 1 91 0 02 McCausland et al 2011 Degraded Measured via laser imaging Literature 1 66 0 06 McCausland et al 2011 After Hildebrand et al 2006 and Zolensky et al 2002 TL P10 a 1 64 0 10 Hildebrand et al 2006 Pristine Bulk volume measured by Archimedean bead method grain volume density measured with commercial helium pycnometer TL P11 a 1 61 0 05 Hildebrand et al 2006 Pristine Methods ibid TL 425 RB 1 68 0 04 39 2 Hildebrand et al 2006 Presumed degraded Methods ibid TL 5 ET 01 1 67 0 05 Hildebrand et al 2006 Presumed degraded Methods ibid TL 15 ET 06 1 61 0 10 37 6 Hildebrand et al 2006 Presumed degraded Methods ibid TL P2 1 78 0 05 35 4 Hildebrand et al 2006 Pristine Methods ibid Vein present TL 26 PM 03 1 69 0 07 42 3 Hildebrand et al 2006 Presumed degraded Methods ibid Fragment Bulk density Error Porosity Error Source Notes g em g em TL 381 PB 11 1 58 0 05 43 2 Hildebrand et al 2006 Presumed degraded Methods ibid TL 410 HP 23 1 71 0 06 38 2 Hildebrand et al 2006 Presumed degraded Methods ibid TL 137 RC 07 1 59 0 05 41 2 Hildebrand et al 2006 Presumed degraded Methods ibid Hildebrand 1 64 0 02 40 1 Hildebrand et al 2006 Weighted mean of previous samples excluding P2 as it had a vein average Zolensky 1 66 0 08 Zolensky et
60. sity were measured for a suite of 13 fragments The bulk volume of the fragments was measured with a laser camera Scan ning the meteorites and assembling their models was not a challenge during this project per se A similar metrology system was used by McCausland et al 2011 for three degraded Tagish Lake specimens and laser scanning has been used for a variety of stony meteorites previously such as a detailed study of the H4 Buzzard Coulee Fry et al 2013b The greater challenge during this project was to successfully oper ate the apparatus in a cold room This very expensive instrument does not have elec tronics that are designed for the cold environment in which Tagish Lake is kept so it was critical to design a method of protecting the camera The final design was based on insulation provided by thermal blankets which work by radiating heat back to its source Foam pads were placed on the camera to create air pockets and to prevent the blankets from obstructing the lens areas The blankets were wrapped in several layers around the camera This protection allowed two hours of work in a cold room at 10 C While the design was eventually improved to allow for the camera body to be sufficiently warm past two hours the exposure of the lens areas became the limiting factor for the cold room session length as some hardware in that area of the camera likely a charge coupled device began to malfunction The grain volume which is combi
61. st The camera is wrapped as per test 3 and appendix II It is placed in the cold room plugged in and attached to the laptop After the scanning is complete is it removed from the cold room per the procedures in test 3 and appendix II The gathered scans will be processed in MATLAB The scans will be cropped to only show the rectangular surface They will imported into the MATLAB where a script will perform Principal Component Analysis PCA on the point cloud A plane will be fitted through the three dimensional point cloud The script will compute the deviation of the point cloud from the fitted plane a scan is judged to be of higher quality if the deviation is smaller Ideally there will be no correlation between the deviation and time and or temperature Same as test 3 The temperature gathered will be for the camera and not the lenses The gathered scans for this tests should be saved for data analysis A consistent filename format will be helpful PCA_test4_ lt date gt _ lt iteration gt lt scan gt asc Critical steps 76 Description Initials and date Note Outside temperature C Outside humidity Inside temperature C Calculate Dewpoint gt C Attach foam pads to camera Attach thermocouples to camera Wrap with thermal blanket Add extra layers optional Set up timer Set up calibration chart Set up laptop in cold room Wrap laptop in spare t
62. st will start with an initial temperature outside the cold room The camera will be placed into the cold room and temperature time data will be recorded When the critical temperature is reached the camera is removed from the cold room and the temperature time data is still recorded until the camera re equilibrates When the camera is removed from the cold room it will be unplugged because there is no need to run scans The laptop is placed first in the cold room and readied for scanning The laptop will be wrapped in a thermal blanket to keep it warm although the risk is not major because it is unlikely that test will run for a long time The camera is placed into the cold room with the attached thermocouples It is plugged in turned on and connected to the laptop At this point the usual scanning rhythm will begin Temperature time data will be recorded manually The data will be then entered into a spreadsheet and graphed As the camera is now operating the critical temperature is depending on the operating range which is further limited Because the thermal response of the camera is known beforehand it will be possible to predict the approximate time needed to cool down the critical temperature The gathered scans for this test are immaterial The expected temperature change and contrast will be larger than the optimal conditions of test 3 care has be taken to watch for condensation Critical steps 70 Descripti
63. t P 10a with the fusion crust now facing The model is representative of the fragment the transition from fusion crust to broken sur face is clearly visible and the sub millimetre scale surface roughness in the fusion crust is seen The fragment that was by far the most challenging to scan and assemble was P 4 a model is shown in Figure 18 An oriented individual with a nearly complete fu sion crust it is characterized by a very bumpy and pitted surface Furthermore it is very rounded and uniform in its texture The combination of these features made it difficult for the program to align the scans together and for the operator to guide it due to a lack of salient features It is also the only fragment for which extra scans were required The complexity of the geometry is reflected in the high standard devia tion result obtained for the final model of 0 12 mm For comparison the average stan dard deviation among the 13 fragments was 0 072 0 018 mm one standard devia tion and the closest standard deviation to that of P 4 was for P 10a which had a value of 0 091 mm see also Appendix B The density result obtained for P 4 1 81 0 04 g cm is reasonable In con 54 trast the porosity was the highest out of any of the 11 measured fragments at 38 2 Per Table 1 and Figure 13 the porosity of P 4 is comparable to that of the degraded samples This discrepancy in porosity can be explained by the unusual fusion crust texture but m
64. t be warmed above 10 C As such precautions needed to be taken as to not damage this expensive in strument Both direct and indirect effects of the cold needed to be considered Di rectly the cold may cause internal components to malfunction For example moving parts may get damaged if the lubricant freezes or otherwise loses its ability to reduce friction Alternatively various parts calibrated at room temperature may lose their ac curacy in the cold Indirectly the cooling of the air can cause condensation which is most detrimental to the integrity of the instrument if it occurs inside the enclosure Dewpoint To avoid damaging the instrument the interior of the instrument has to be kept above the dewpoint and within the operating range The dewpoint for an initial tem perature and humidity is defined as the temperature at which a body of air becomes supersaturated with respect to water vapour simply it is the temperature at which condensation starts to occur The intended operating conditions for the Vivid 91 cam era are indoors the manufacturer gives specification based on a calibration tempera ture of about 20 C with a relative humidity under 65 The dewpoint at typical in door conditions is approximately 10 C which conveniently is at the bottom of the in strument s operating range The dewpoint can be predicted by solving the Clausius Clapeyron equation 20 which describes phase transitions in pressure temperature
65. t up of three orientations plus extras to cover any difficult areas The rotation increment will depend on the size and geometry of the target The flat chart will be scanned to test the camera s optics at the beginning and end of each sample The temperature of the instrument will be monitored throughout the scan The camera is wrapped as per appendix II It is placed in the cold room plugged in and attached to the laptop outside After the scanning is complete is it removed from the cold room per the procedures in appendix II The gathered data will be saved as cdk files These will opened at a convenient time to export as asc files The asc point clouds will be assembled in Poly Works as would be done under standard conditions The flat chart scans will analyzed in Matlab Same as part A test 3 Specifically condensation in camera if it is overcooled condensation on lenses if they are not protected other damage to electronic components as a consequence of the cold Temperature time data will not recorded only temperature will observed as to not remain in cold room too long Critical steps 80 Description Initials and date Note Sample Outside temperature C Outside humidity Inside temperature C Calculate Dewpoint CE Critical temperature C Prepare camera for cold room cf Appendix II Set up timer Prepare laptop and connection outside cold room Set up obs
66. th multimeters taking readings from thermocouples C and a sample on the turntable R Appendix III Time temperature recording sheet 85 Time min Temperature C Time min Temperature C Appendix B Raw data outputs 86 Fragment Bulk volume Grain volume Standard deviation Scans Scans cm cm mm made used P 1 91 915990636 0 071 54 12 P 10a 61 787840183 0 091 54 12 P 4 33 201370222 21 091 0 12 57 20 P 7 24 821445238 16 9005 0 07 54 9 P 6 18 531633266 13 1951 0 056 41 15 P 10b 13 918117098 9 75508 0 061 36 12 P 9b 11 545186063 8 30674 0 053 54 16 P 9a 9 803724927 7 20048 0 065 42 16 P 11b 7 159154791 5 14552 0 079 27 12 P 3a 6 075417573 4 35906 0 058 42 13 P 5a 5 042105227 3 7557 0 077 53 11 P 11r 5 071518165 3 64868 0 081 54 13 P 11c 4 574523923 3 30912 0 057 51 14 This table lists the raw output given by the respective instruments and programs the digits given are by no means all valid The bulk volume measurement is accurate to approximately 1 of the value The grain volume measurement is accurate to at least 0 6 of the value The standard de viation is accurate to two significant figures 87 Appendix C Raw scan and model data Appendix C is an included disk containing raw scan model data and a PDF file of this thesis There are
67. the tests is to determine how long can the camera survive in the cold room based on a standard starting temperature The survival of the camera is specifically regulated by one of two temperatures either the bottom end of its operating range i e 10 C or the dewpoint whichever one is reached first If the camera s electronics are cooled to 10 C then they are prone to malfunctioning Otherwise if the camera is cooled to its dewpoint condensation may form which would also damage the electronics The dewpoint must be considered from two points during the tests when the instrument has cooled down and when it warms up If the air within the instrument circulates poorly then the warm air within it will cool and lose its ability to maintain its vapour content hence causing condensation If circulation within the instrument is good condensation when cooling is not a likely problem but at the same if cold air is circulated within the instrument it will reach the 10 C barrier more quickly When the instrument warms up the warm air that surrounds it may get cooled below its dewpoint or it will cool when it passes through the camera in both of these scenarios the cooling may be sufficient to cause condensation and thus damage to the camera The testing of the camera will involve designing a a method of insulating the camera against the cold as to prolong the time it can spend inside the cold room three groups of tests will be devoted
68. to this goal One test will show the quality of the scans and the last test will be an attempt to scan an object similar to the Tagish Lake meteorite Thermocouple SENSOr area Light receiving E i r Laser emitting wind Electronics Optics eon Figure 1 Diagram of Vivid 9i from the user manual The camera is separated into the optics in the front and electronics in the back the side shown is the cable side 63 Objective Location Date Equipment List of tests Definitions Common 64 To determine the thermal response of the Konica Minolta Vivid 9i laser camera for operation in a cold room The camera will be subjected to five kinds of tests to demonstrate its fitness as an instrument that can be used to make precise measurements in a cold room The tests will be conducted at Carleton University A walk in cold room will be used for all tests that need to be conducted at low temperatures For the warm up component of a test that follows a period of time spent in the cold room the camera will be located in the room that contains the walk in cold room The cold room is located at the Steacie Building in Dr Tim Patterson s lab Any test that does not require time spent in the cold room can be conducted in the usual lab Herzberg Building The tests will start upon approval of the plan arrival of all necessary equipment and final confirmation of space availability It is
69. toring in 21 the change in the enthalpy of vaporization with temperature Equation 11 is rear ranged and integrated to give a result for es LIR 12 este where C is a constant of integration Equations 9 10 and 12 are combined to give an expression for dewpoint temperature Ta RH LIR w T T 1 a The psychrometric chart is a plot of dewpoint Ta versus initial temperature T for a various relative humidities Figure 4 gives the chart for relative humidities from 10 to 100 in increments of 10 the principal advantage of the chart is that it avoids the long and arduous calculations required to calculate dewpoint directly from the closed approximate solution Psychrometric chart Dewpoint C 10 20 Air temperature C 30 Figure 4 A psychometric chart was used to determine the dewpoint after measuring the room temperature and humidity 40 22 23 Camera The camera generates heat during operation and it is equipped with a fan that cools it when it operates in warm conditions The fan works vigorously even in the typical lab setting where temperatures are seldom higher than 25 C As the tempera ture sensitive parts of the camera are within its enclosure as long as the interior of the camera is kept within the operating range and above the dewpoint there should be no problems with regards to the operation of the instrument A major goal of this project became to design a way to maxi
70. unpredictably because of the cold As it was too cold rows in the data matrix 36 were not being sent to the receiving laptop This problem manifested itself the most when there was a break taken for scanning e g to allow access to the pycnometer This erratic behavior cannot be completely prevented because parts of the camera must be exposed for it to capture images The timing of this behavior is not entirely understood as it was identified very late in the process of using the camera and not enough time was available to properly diagnose and resolve the problem Two hours of scanning is feasible but there is some risk of data corruption to wards the end The risk can be mitigated by operating the camera s electronics contin uously as much as possible but two hours of exposure starts to become as much a risk to the integrity of the camera as it does to the safety of the operator 37 4 Results In total thirteen meteorites were imaged with the laser camera and eleven of these were measured with the pycnometer The two that were not measured with the pycnometer were too large to fit into it The results for bulk density and porosity for 13 pristine Tagish Lake fragments are given in Table 2 a graph of porosity as a function of bulk density is presented in Figure 10 for the eleven samples for which both measurements are available The raw results which include the raw bulk volume and standard deviation output from Poly wor
71. used for samples smaller than 5 cm as the experimental uncertainty becomes too great nor can be it used for very fragile 14 or friable samples In addition because the beads are observably compressible true Archimedean fluids are not the method is fraught with systematic error McCausland et al 2011 Given the friable nature of Tagish Lake and the small size of several important fragments using the beads method was not an option Furthermore Tagish Lake is very porous and there was a risk of irreversible contamination even by the beads There are other techniques to measure volume in addition to the Archimedean method The meteorite can be cut into a simple shape such as a cube Alternatively the sample can be packed into a known volume of clay and molded into a simple shape The volume of the meteorite becomes the difference between the total volume and the volume of the clay The clay method risks contamination of the sample and introduces inconsistencies in molding the clay around the sample Both of these methods are destructive Britt and Consolmagno 2003 As a result laser imaging which only requires contacting the meteorite to change its position was the only truly non destructive method available measuring the density of the Tagish Lake meteorite There are nonetheless disadvantages to this method It takes several hours to obtain a density result for a single fragment over an hour is needed just to build a lib
72. y 1 5 times the pressure outside the instrument When the sample chamber equilibrates the valve is opened which equalizes the pressure The initial and final pressures are measured It is assumed that the helium behaves as an ideal gas Furthermore it is assumed that temperature and the amount of gas in the system is constant if these assumptions are not met the results will be affected As such the ideal gas law PV nRT 5 where P is pressure V is volume n is the number of moles of gas R is the ideal gas constant and T is temperature is reduced to Boyle s law PV k 6 where k is a constant or alternatively PV PV 7 The volume of gas introduced into the apparatus before the valve is opened is the 17 difference between the volume of the sample chamber V and the grain volume of the sample V assuming the reference chamber is evacuated the volume of gas after the valve has been opened is the difference between the sum of the volumes of the two chambers V V and the grain volume of the sample Substituting into equation 7 for an initial pressure P and the final pressure Ps the following is obtained P V V P VtVi V 8 Rearranging equation 8 equation 3 is obtained as a solution for the grain volume of the sample neie LXV et Pepp 3 The instrument in question the Ultapyc 1200e does 15 runs in total It must first thermally equilibrate before any runs are done as it applies the ideal gas
73. z ing the samples because of the possibility of damaging the internal structure of sam ples during the freeze thaw cycle Both samples were scanned at room temperature one was imaged while the camera was not wrapped 0122 11 whereas the other one was imaged with the camera wrapped up 0112 6 The purpose of this test was to demonstrate that the camera could be used to yield good results while under the extra gear Density measurements for the samples were statistically identical 2 93 40 03 g cm in both cases The assembly of these two models was simple in comparison to the models of the coals Conclusion and addendum The cold room tests at Carleton showed that it is possible to insulate the cam era in such a way that it could last approximately two hours in a cold room below 10 C without reaching a critical temperature It was demonstrated that the camera s optics do not show any ill effects due to the cold over the time period it is placed in the cold room Finally it was shown that it should be feasible to image the Tagish Lake meteorite in the cold room at the University of Alberta in Edmonton In turn the 35 3D models assembled from the scans could be used to determine a meteorite frag ment s bulk volume from which bulk density and porosity may be determined In Edmonton the design protected the camera body from the cold and 13 me teorites were successfully imaged over a period of four days 2 July 5 July How

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