Cooking Martian Soil with IGOR: TEGA and the Mars Phoenix ... · Cooking Martian Soil with IGOR:...

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Cooking Martian Soil with IGOR: TEGA and the Mars Phoenix Lander Summary Calcium carbonate has been identified in the soils of the north polar regions of Mars and is present in one subsurface sample at a level of about 3% to 5% by weight. Abstract Calcium carbonate (3 to 5 wt. %) has been identified in the soils by an endothermic transition beginning around 735 °C accompanied by evolution of CO2 and by the ability of the soil to buffer acid addition at a pH of 8.2 ± 0.5. Based on empirical kinetics, the amount of calcium carbonate is most consistent with formation in the past by the interaction of atmospheric CO2 with liquid water films on particle surfaces. Using IGOR IGOR converted the raw TEGA data from a long list of voltage, ion count, and timestamps into multiple series of 5 or 7 point x-y mass curves centered on the masses of interest, and then curve-fit these to determine the amplitude at the corresponding time. 10000 8000 6000 4000 2000 0 Count rate (counts/sec) 12x10 3 11 10 9 8 7 TEGA Time (sec) 1600 1400 1200 1000 800 600 400 200 0 Oven temperature (°C) <<??>>"%s",winreference()} Wicked Witch Mass 44 rate (Sol 068) Mass 44 rate (Sol 070) Rate difference Oven temperature Plot of Mass-44 (CO 2 ) count rate and temperature vs. run time. e first peak is atmospheric CO 2 that diffuses into the oven and plumbing overnight; the second may be due to carbonates with a low decomposition temperature (e.g. FeCO 3 or MgCO 3 ). e high temperature peak is due to CaCO 3 . David K. Hamara, University of Arizona IGOR was central to the operation of the Phoenix TEGA instrument. Each evening on Mars, Phoenix would transmit the entire day’s data to Earth in one burst. From the time the data arrived, the TEGA team would typically have 20 – 30 minutes to process the data and give a full instrument health and status report. e entire day’s data would be loaded into IGOR, and the IGOR code would automatically: Compare all command completion messages with the sent commands, printing out a report showing the exact execution time of each command and flagging any commands that failed. Convert the engineering data to useful units, compare each value against high and low alarm limits, and print an instrument health report including plots of certain critical channels. Process the data from the ovens into a power profile, fit a curve to the profile, and display deviations from the expected profile that indicate phase changes in the sample. Assemble the raw data from the mass spectrometer (a list of deflection voltages and ion counts) into a useful form, locate the special calibration sweeps interspersed in the data and track the calibration vs. time, measure the amplitude of each peak in each science sweep, and assemble time histories of the amplitudes for each mass. Since the mass spectrometer ran on its own clock, time-correlate the oven and engineering data with the mass spectrometer data. Custom GUI (an IGOR control panel) designed temperature profile commands uplinked to the Phoenix Lander’s TEGA oven. After examining the previous day’s data for roughly two hours, the TEGA team would use the IGOR ramp generator code to construct the temperature profile for the next run and create the command file to be uplinked to Phoenix the following Martian morning. IGOR also automatically produced the required project paperwork for signoff. Evidence for Calcium Carbonate at the Mars Phoenix Landing Site W. V. Boynton, D. W. Ming, S. Kounaves, S. M. M. Young, R. E. Arvidson, M. H. Hecht, J Hoffman, P. B. Niles, D. K. Hamara, R. C. Quinn, P. H. Smith, B. Sutter, D. C. Catling, R. V. Morris, and the Phoenix Science Team

Transcript of Cooking Martian Soil with IGOR: TEGA and the Mars Phoenix ... · Cooking Martian Soil with IGOR:...

Page 1: Cooking Martian Soil with IGOR: TEGA and the Mars Phoenix ... · Cooking Martian Soil with IGOR: TEGA and the Mars Phoenix Lander Summary Calcium carbonate has been identified in

Cooking Martian Soil with IGOR:TEGA and the Mars Phoenix Lander

Summary

Calcium carbonate has been identified in the soils of the north polar regions of Mars and is present in one subsurface sample at a level of about 3% to 5% by weight.

Abstract

Calcium carbonate (3 to 5 wt. %) has been identified in the soils by an endothermic transition beginning around 735 °C accompanied by evolution of CO2 and by the ability of the soil to buffer acid addition at a pH of 8.2 ± 0.5. Based on empirical kinetics, the amount of calcium carbonate is most consistent with formation in the past by the interaction of atmospheric CO2 with liquid water films on particle surfaces.

Using IGOR

IGOR converted the raw TEGA data from a long list of voltage, ion count, and timestamps into multiple series of 5 or 7 point x-y mass curves centered on the masses of interest, and then curve-fit these to determine the amplitude at the corresponding time.

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<<??>>"%s",winreference()}

Wicked Witch

Mass 44 rate (Sol 068) Mass 44 rate (Sol 070) Rate difference Oven temperature

Plot of Mass-44 (CO2) count rate and temperature vs. run time.

The first peak is atmospheric CO2 that diffuses into the oven and plumbing overnight; the second may be due to carbonates with a low decomposition temperature (e.g. FeCO3 or MgCO3). The high temperature peak is due to CaCO3.

David K. Hamara, University of ArizonaIGOR was central to the operation of the Phoenix TEGA instrument. Each evening on Mars, Phoenix would transmit the entire day’s data to Earth in one burst. From the time the data arrived, the TEGA team would typically have 20 – 30 minutes to process the data and give a full instrument health and status report. The entire day’s data would be loaded into IGOR, and the IGOR code would automatically:• Compare all command completion messages with the sent commands, printing out a report showing the exact execution time of each command and flagging any commands that failed.• Convert the engineering data to useful units, compare each value against high and low alarm limits, and print an instrument health report including plots of certain critical channels.• Process the data from the ovens into a power profile, fit a curve to the profile, and display deviations from the expected profile that indicate phase changes in the sample.• Assemble the raw data from the mass spectrometer (a list of deflection voltages and ion counts) into a useful form, locate the special calibration sweeps interspersed in the data and track the calibration vs. time, measure the amplitude of each peak in each science sweep, and assemble time histories of the amplitudes for each mass.• Since the mass spectrometer ran on its own clock, time-correlate the oven and engineering data with the mass spectrometer data.

Custom GUI (an IGOR control panel) designed temperature profile commands uplinked to the Phoenix Lander’s TEGA oven.

After examining the previous day’s data for roughly two hours, the TEGA team would use the IGOR ramp generator code to construct the temperature profile for the next run and create the command file to be uplinked to Phoenix the following Martian morning. IGOR also automatically produced the required project paperwork for signoff.

Evidence for Calcium Carbonate at the Mars Phoenix Landing Site

W. V. Boynton, D. W. Ming, S. Kounaves, S. M. M. Young, R. E. Arvidson, M. H. Hecht, J Hoffman, P. B. Niles, D. K. Hamara, R. C. Quinn, P. H. Smith, B. Sutter,

D. C. Catling, R. V. Morris, and the Phoenix Science Team

Page 2: Cooking Martian Soil with IGOR: TEGA and the Mars Phoenix ... · Cooking Martian Soil with IGOR: TEGA and the Mars Phoenix Lander Summary Calcium carbonate has been identified in

TEGA was a combination high-temperature furnace and mass spectrometer instrument for analyzing martian ice and soil samples. The robotic arm delivered unique samples of soil and ice into eight tiny ovens about the size of an ink cartridge in a ballpoint pen. Each oven was used only once. Each sample was sealed in an oven and the temperature slowly increased while the power required for heating was carefully and continuously monitored. This scanning calorimetry process shows the transitions from solid to liquid to gas of the different materials in the sample, which reveals the chemical character of the soil and ice. As the temperature of the furnace increased up to 1000°C (1800°F), the ice and other volatile materials in the sample were vaporized into a stream of evolved gases that were analyzed by a mass spectrometer capable of detection levels down to 10 PPM to identify minute quantities of organic molecules in the ice and soil.

The TEGA was built by a team at the University of Arizona, led by Dr. William Boynton

and at the University of Texas, Dallas by Dr. John Hoffman.

Igor Finds Water on Mars:GRS and the Mars Odyssey Orbiter

David K. Hamara, University of Arizona

The Boynton group has been using IGOR to process gamma ray spectra since the ill-fated Mars Observer mission in the early 90’s. We used IGOR version 2 to interactively fit simple Gaussian curves to the Mars Observer data and calculate the peak areas.

The Mars Observer cruise data showed a serious deficiency in this model. Radiation damage to the detector crystal caused the peak shape to deviate significantly from a Gaussian, leading to large errors in determining the area. For the Mars Odyssey GRS, we developed a new peak shape model, where the high-energy side of the peak is Gaussian and the low energy side is an exponential.

We developed IGOR code to fit this new peak shape to multiple, overlapping peaks, and this forms the basis for the current Odyssey GRS data reduction package.

Mars is very stingy with its gamma rays. For our “strong” peaks, we only see one gamma ray every 10 seconds, and for weak peaks, we see one gamma ray every 10 or more minutes. When we then divide Mars into smaller “pixels” for mapping, the statistics in each pixel are very poor. There are far too many free parameters in this equation to properly fit the peaks in the individual pixels. To solve this problem, we sum all of the spectra over the entire planet and fit each peak in this sum to get a good measure of the peak shape. We then fix all of the parameters except the amplitude when fitting the peaks in the individual pixels.

We also frequently use IGOR as a development environment for algorithms that we have no intention of running in IGOR. IGOR gives us a C-like language, a convenient debugger, and an interactive environment for evaluating the results. Once we are convinced that the algorithm is correct, it is quite easy to translate IGOR functions to C. We used IGOR to develop the code for correcting the spectra for gain and offset drift. That code is now integrated into the Oracle database that organizes and stores all of the spectra. We also used IGOR to develop the “forward model” code – a Monte Carlo simulation that predicts how many counts we should see in a given peak assuming a certain model of Mars.

Custom Interface for simultaneous fitting of multiple overlapping unique peak shapes.

The Gamma Ray Spectrometer (GRS) is a set of instruments aboard the 2001 Mars Odyssey spacecraft which detects gamma ray photons coming from the planet.

The information collected by GRS is being used to help determine the composition and location of the elements on Mars, including production of a global map of water deposits and other elements on Mars, an estimation of the depth of water deposits, and continued study of how seasons affect the polar ice caps. GRS will also contribute to the study of cosmic gamma ray bursts.

The TEGA was built by a team at the University of Arizona, led by Dr. William Boynton and at the University of Texas, Dallas by Dr. John Hoffman.