Spectral Characterization of Venusian Surface Mineralogy Johnathon Conley University of Arkansas, Fayetteville

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5-2011 Spectral characterization of Venusian surface mineralogy Johnathon Conley University of Arkansas, Fayetteville

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Spectral Characterization of Venusian Surface Mineralogy

An Honors Thesis submitted in partial fulfillment

of the requirements of Honors Studies in Mechanical Engineering

Johnathan William Conley

Spring 2011

Mechanical Engineering

College of Engineering

The University of Arkansas

Acknowledgements

I am greatly appreciative of Dr. Vincent Chevrier’s invaluable help and advice throughout the research project. His expertise helped the project advance toward meaningful goals. I am also thankful for the help of Dr. Larry Roe of the Mechanical Engineering Department for guidance as the Director of the Arkansas Center for Space and Planetary Sciences during part of the research as well as his advice as a professor and mentor. Without the contributions to the project from other members of the research team including Patricia Gavin and Erika Kohler, the project would not possible. The support of NASA through the Arkansas Space Grant Consortium is also greatly appreciated.

Table of Contents Acknowledgements...... 2 List of Figures ...... 4 List of Tables ...... 4 Introduction ...... 5 Previous Missions ...... 6 Zond ...... 6 Mariner ...... 6 Venera ...... 7 Pioneer-Venus ...... 8 Upcoming Missions ...... 8 Venus Flagship Mission ...... 8 European Venus Explorer ...... 10 Venus Mobile Explorer ...... 10 Venus In-Situ Explorer ...... 10 Spectral Analysis ...... 10 Greenhouse Effect ...... 13 Mineralogy ...... 14 Goals ...... 14 Materials and Methods ...... 15 Materials ...... 15 Sample Preparation ...... 15 Spectroscopy ...... 16 Results and Discussion ...... 17 Near-Infrared Results ...... 17 Conclusions ...... 23 Bibliography ...... 24

List of Figures Figure 1 Mariner 2 (National Aeronautics and Space Administration) ...... 6 Figure 2 Infrared image of Venus by Mariner 10 (Pioneer, 1979) ...... 7 Figure 3 Locations of Venera landings with surface topography. The Vega missions shown on the graphic are minor Venus landers but are not discussed in this paper. (Mapa de Sondas Sobre Venus, 2007) ...... 7 Figure 4 Venera 14 images of the surface (Schombert, 2010) ...... 8 Figure 5 Concept Lander Descent Profile (Jet Propulsion Laboratory, 2009) ...... 9 Figure 6 Concept Image of a Venus Flagship Mission Lander (Venus Exploration Analysis Group, 2009) ...... 9 Figure 7 Schematic of FTIR mechanisms (Thermo Nicolet Corporation, 2001) ...... 11 Figure 8 - Michaelson Interferometer (Gammon, 2006) ...... 12 Figure 9 Venusian Greenhouse Effect (Bechtold, 2006) ...... 14 Figure 10 NIR-Olivine ...... 18 Figure 11 NIR-CPx3 ...... 18 Figure 12 NIR - Enstatite ...... 19 Figure 13 NIR - Olivine Forsterite ...... 19 Figure 14 NIR - OPx ...... 20 Figure 15 NIR - Kieserite ...... 21 Figure 16 NIR - Augite ...... 22 Figure 17 NIR - Olivine Dunite ...... 23

List of Tables Table 1 - Silicates ...... 15 Table 2 - Sulfates ...... 15

Introduction While the atmospheric chemical composition of the Venusian atmosphere has been characterized at length by probes and ground-based equipment, the surface mineralogy of Venus is not yet well understood. The extremely thick atmosphere of Venus shields the surface from direct observation. While radar imaging of the surface reveals surface morphology, surface composition is difficult to characterize at a distance. Observation is also difficult due to the intense temperature (approximately 480°C) and pressure (approximately 90 atm) found on the surface. This has prompted NASA and other institutions around the world to begin planning for new missions to land on the surface of Venus to better understand its composition, structure, and other features.

As a “sister” planet to Earth in terms of size and mass, Venus provides an interesting object of study for comparison (Landis, 2006). Though similar in bulk, Venus’s surface is dramatically different than Earth’s. Instead of liquid water and temperate climates, Venus is covered by a thick cloud layer and scorching winds. Even though it is close to being in Sol’s habitable zone, the surface is not remotely conducive to life. Earlier in the planet’s history, though, it could have been in the habitable zone, but obviously surface conditions have dramatically changed since then. Understanding more about the surface chemistry and mineralogy of the planet will allow scientists to better understand the planet’s history. By understanding Venus’s history, scientists can better understand what caused this dramatic transformation. This will be essential to preventing the same transformations on Earth.

Venus’s atmosphere is the most notable and most studied feature of the planet. The hot, thick mass of swirling gases is not found on any other terrestrial planet. Although scientifically interesting itself, this shroud has made effective study of the planet’s surface difficult. Only limited direct observation is available from the Soviet Venera missions and American Pioneer probes. This makes future landers particularly attractive for extensive surface study.

The destructive conditions found at the surface make direct exploration difficult, though. Landers must be structurally sound enough to survive the intense pressure, and electronics must be able to perform at temperatures hot enough to melt the solder that typically holds them together. Engineering such a craft is difficult, and obtaining useful scientific results to justify the mission is even more so. Without a proper method of analysis and mineralogical characterization, missions to the surface will not be successful. Infrared spectroscopy holds promise to meet the demands of the mission while producing valuable scientific results. As a low-weight, low-power device, an infrared spectrometer would allow scientists to characterize the minerals found of the surface of the planet much more effectively than previously observed. More study is necessary to characterize the response of both minerals and equipment to the high temperatures that will be seen on an actual mission. Most importantly, spectra could change due to temperature-induced changes in crystallization, composition, or other physical characteristics, which will be the focus of this study.

Previous Missions Since the 1970s, more than 20 spacecraft have visited Venus. More spacecraft have been sent to study Venus than any other planetary body. Highlights from these missions are discussed below; due to the number of Venus missions, the missions listed below are primarily those that included landers.

Zond Zond 1 was a failed mission sent to the planet by the Soviet Union in 1964. The craft would have landed on the surface of the planet, but an electronics malfunction prevented mission success.

Mariner Sent by the United States, the Mariner missions were the first successful missions sent to Venus. Mariner 2 flew by Venus in 1962 and measured the atmospheric temperature and magnetic field of the planet. The spacecraft orbited 34,773 km above the planet and carried infrared and microwave radiometers. The craft revealed both the hot surface and relatively cool upper cloud layer of the planet. This was the first direct measurement of Venus’s temperature. Mariner 2 also revealed the planet had little or no magnetic field or radiation belts. Mariner 2 was the first successful interplanetary spacecraft and is still in orbit around the sun.

Figure 1 Mariner 2 (National Aeronautics and Space Administration)

The image below is an infrared image of Venus, revealing the high-level winds in the upper atmosphere of the planet.

Figure 2 Infrared image of Venus by Mariner 10 (Pioneer, 1979) Venera The Soviet Venera 3 mission became the first spacecraft to reach the Venusian surface in 1966. Unfortunately, this was a crash landing, so the mission was not considered a success. Future Venera missions, though, were more successful. Venera 5 and 6 sampled the atmosphere during descent, but failed before landing. Venera 7 and 8 successfully landed, and 9 and 10 returned images of the planet’s surface. Venera 13 and 14 were the most successful and lasted on the surface for almost an hour each (Surkov, 1983).

Figure 3 Locations of Venera landings with surface topography. The Vega missions shown on the graphic are minor Venus landers not discussed in this paper. (Mapa de Sondas Sobre Venus, 2007)

Figure 4 Venera 14 images of the surface (Schombert, 2010) Pioneer-Venus Though primarily an atmospheric science package, Pioneer- Venus 2 included a “multiprobe” consisting of four separate entry craft that sampled the atmosphere on the way down to the planet’s surface. The released probes did not land in a survivable manner, but they did set a precedent for the “flotilla” proposed in the Venus Flagship Mission currently in planning.

Upcoming Missions

Venus Flagship Mission NASA has not sent a major mission to Venus since the Magellan probe in the early 1990s. NASA has never sent a landing craft; only atmospheric probes have been inserted from orbit. Based on planning from the National Research Council Decadal Survey and the Solar System Exploration (SSE) Roadmap, NASA has begun more serious planning for a flagship-level mission to Venus for launch in approximately 10 years. This mission would include a surface landing component since the surface is so poorly understood. As planned by the NASA Jet Propulsion Laboratory at the California Institute of Technology, the Venus Flagship Design Reference Mission currently includes an orbiter, two balloons, and two landers. This landing party would link with the orbiter overhead for radio communications. Balloons would sample gases while circumnavigating the planet in the high-speed winds of the upper atmosphere. Landers would obtain a profile of atmospheric conditions on descent. When on the surface, mineralogical studies of the surface and slightly below the surface would be taken, and panoramic cameras would provide a visual profile of surface morphology.

The landers would be constructed of advanced materials to survive on the surface for at least five hours. The primary pressure vessel would be a 0.9 m diameter titanium shell with a

8 wall thickness of 1 cm. A combination of phase-change lithium nitrate material and silica insulation protects the interior of the craft from the high surface temperatures. The payload mass of the craft would be 106.2 kg, and power would be provided by lithium-thionyl chloride batteries only. This restricts the bulk of scientific instruments that can fly on the mission, so small and low-power equipment like a fiber optic Fourier-Transform InfraRed (FTIR) probe are ideal.

Figure 5 Concept Lander Descent Profile (Jet Propulsion Laboratory, 2009)

Figure 6 Concept Image of a Venus Flagship Mission Lander (Venus Exploration Analysis Group, 2009)

European Venus Explorer The European Venus Explorer mission is planned to be a collaborative effort between the European Space Agency, Japan, Russia, Canada, and the United States (E. Chassefière, 2008). Russia would build the lander that would characterize the surface chemistry of the planet. This would be accomplished through visual imaging and gamma ray spectroscopy.

Venus Mobile Explorer The VME mission is planned to be a combination lander and metallic bellows balloon (Glaze, et al., 2009). The bulk of the scientific package is on the bellows portion of the lander and is in the early stages of planning, but currently a near-infrared spectrometer is included in the package that would be used for surface morphology and stratigraphy.

Venus In-Situ Explorer In preparation for a possible Venus Surface Sample Return (VSSR) mission, the Decadal Survey began planning for a mission to target Venusian geochemistry. This mission is planned to be part of the New Frontiers program, making it a smaller scale mission than a flagship-class mission. Importantly, though, it is still likely to include near-IR spectroscopy equipment onboard for surface material characterization.

Spectral Analysis Previous missions have been unable to effectively characterize mineralogy on the surface. Even when landers have been employed, the scientific equipment on board has not been fast enough or accurate enough to allow broad observation. By using an infrared spectrometer to take measurements of mineral properties, future landers can yield better and more conclusive results.

In spectroscopic analysis, light from a known source is emitted toward the sample, which is then absorbed or transmitted depending on the chemical composition of the sample. Some radiation might also be reflected or refracted in a specific way depending on surface morphology and crystal structure. By crushing the sample into a powder of standard size, the effects of surface interference are minimized. This leaves actual mineralogy as the primary source of light interference. The raw output of the light detector is compared to a background to normalize the data output.

A commonly used form of infrared spectroscopy is Fourier-Transform InfraRed (FTIR) spectroscopy. FTIR spectroscopy allows identification of specific chemical compounds and groups. FTIR spectroscopy was created because of problems with the older technology of dispersive spectroscopy, including optical losses and signal degradation.

Infrared light is the band of the electromagnetic spectrum with wavelengths ranging from 0.7 to 500 µm, which falls between the visible and microwave spectrums. During the spectral analysis, infrared radiation is emitted from a pure, known source in a focused manner toward the sample. A certain amount of the incoming radiation is absorbed and a certain amount is reflected by the sample, creating a signature “fingerprint” of the substance. This

10 fingerprint is uniquely identifiable and repeatable, which makes identification of the sample's composition possible. When a photon strikes an atom of the sample, it can be absorbed. This absorption can only occur when the radiation causes the dipole moment of a molecule to change or when the incoming photon has enough energy to jump to the next quantized energy level. Photons can also be reflected back to a detector. This reflected light goes through a “random walk” that creates unique spectral features for specific frequencies, depending on the crystal and grain structure of the mineral. The absence or presence of different frequencies seen in the reflected light gives the “fingerprint” of the mineral.

Infrared spectrometers typically have a ceramic infrared source, which can be considered a black body source. This ceramic is heated until it begins to glow, which gives a controllable and steady infrared source. In more modern setups, though, this ceramic source has been replaced by lasers. Lasers have lower cooling requirements and more predictable, focused, and coherent beams. Helium-neon (HeNe) lasers are the most common. For the test setup used in this research, a quartz/halogen source was used. This source uses fluorescent gases and quartz to produce stable light. A dispersive element is used to filter the light from the source to meet specific test objectives. Usually this element is a coated lens or a prism. Gratings are also used in modern detectors to produce better frequency separation. The optics of the spectrometer are based on the Michelson Interferometer. This device splits a beam of light into two different beams that are then directed along two different paths. After traveling their respective paths, the beams are then recombined and a fringe interference pattern is produced.

Figure 7 Schematic of FTIR mechanisms (Thermo Nicolet Corporation, 2001)

Figure 8 - Michaelson Interferometer (Gammon, 2006)

As seen in Figure 8, light is emitted from the source. This single beam is split into two separate beams by the beam splitter (S) which transmits 50% of the light to the first mirror (M1), which is movable, and 50% to the second mirror (M2). A compensator plate (C) is used between S and M2 to make the path lengths between both mirrors equal. The light bounces off of the mirrors and again, 50% of each beam is transmitted. This time, though, each beam is transmitted toward the focusing lens and screen, thus allowing the two beams to recombine. This causes an interference pattern, or interferogram, to be observed on the screen. The complicated signal from the Michaelson interferometer and from interaction with the sample must be reprocessed into a spectrum. This is accomplished through the use of a Fourier transform, thus giving the spectrometer its name.

A spectrometer based on the Michaelson interferometer is able to measure all source frequencies simultaneously, which provides superior detection capabilities. This is known as the Fellget or multiplex advantage. The Fellget advantage allows spectra to be taken relatively quickly, which is essential for a time-limited application like a Venusian probe. This is also known as “signal averaging.” This increases the signal to noise ratio of the data taken, which gives faster and clearer results while eliminating discontinuities in the spectra. From the Fellget advantage, though, arises the Fellget disadvantage; since all frequencies are being measured simultaneously, an error or noise in one part of the spectra will propagate throughout the data.

The use of an interferometer allows the number of moving parts to be greatly reduced, which increases reliability while decreasing data/mechanical losses as well as power and calibration requirements. This makes the FTIR a much more robust setup for inclusion on an interplanetary mission. Only the movable mirror in the interferometer is in constant motion.

Another advantage of interferometer-based spectroscopy is known as the Jacquinot advantage. This concept refers to the relative brightness of the optical setup. In an almost lossless system like an interferometer, the sample is as bright as the source, which increases the amount and accuracy of data collected. This is known as “optical throughput.” This increases the signal to noise ratio of the data. It also means that the resolution of the instrument is constant, since the throughput is constant across frequencies.

Finally, the FTIR is also superior due to the Connes advantage. Since the frequency scale of the source is known very accurately, mirror-moment averaging can be employed to take a great quantity of spectra, which even further increases the signal to noise ratio. Furthermore, since the spectrum of the signal is known discretely, simple mathematics can be used to sort the collated spectral results to obtain spectra of constituent parts.

Since the FTIR cannot obtain spectra directly but instead generates them through the use of a Fourier transform, there can be a slight disadvantage to the use of an FTIR. With modern equipment and techniques, though, this disadvantage can be mitigated.

Since only a single beam is used in most FTIR setups, the system is susceptible to atmospheric interference inside the experimental setup. This atmosphere, which contains CO2 and water vapor, must be purged before use through the use of an inert and transparent gas like N2.

Output from a spectrometer allows characterization of the sample in three major ways: identity, composition, and amount. Location of absorption bands on the spectra gives the identity of the sample. This is the “fingerprint” of that material. Simple math with known spectra allows the spectra of samples with multiple components to be separated into their constituent spectra. Finally, the relative size of the absorption bands gives the amount of each material.

Greenhouse Effect The high temperature found on the surface of Venus is caused by a “runaway greenhouse” effect. When solar radiation strikes the thick atmosphere of the planet, it passes through the gases and strikes the cloud layers, atmospheric gases, and the surface of the planet. Most of the radiation is converted to thermal energy, which is then reflected or transmitted in the form of infrared radiation. The thick cloud layers, though, allow very little infrared radiation to escape. Earlier in the planet’s history, this caused a feedback-looped heating cycle. As the surface of the planet heated up, CO2 and water vapor escaped into the atmosphere. These gases in turn caused more heating, which released even greater amounts of greenhouse gases. This cycle repeated itself, leading to the extremely high temperatures found today on the surface.

The atmosphere of Venus is primarily composed of CO2, which accounts for about 97% of the gases present. The rest is mostly nitrogen, though some other gases are present in small amounts, including water vapor. The thick cloud layer that covers the surface is composed primarily of water vapor and sulfuric acid.

Figure 9 Venusian Greenhouse Effect (Bechtold, 2006) Mineralogy The spectra of a mineral can be affected by several factors including crystallization, powder size, and water content. For minerals that have been exposed to high temperatures, outgassing, phase changes, and other physical changes could greatly affect the spectra of the sampled minerals. The chemical composition could also be affected if sufficient thermal energy was available to trigger internal chemical reactions.

Goals To properly characterize minerals on the Venusian surface, a fast and comprehensive identification method will need to be created to maximize the scientific productivity of a short- lived Venus surface mission. One of the fastest, most accurate material identification systems in common use today is infrared spectroscopy. Before this method can be used accurately on the surface of Venus, though, the effect of Venus’s high temperatures on the collected spectra must be further researched. Using minerals believed to be on the planet, a database of spectra will be generated for further study and comparison.

Materials and Methods

Materials The following tables show the various types of minerals tested. Name, mineral group, Ward’s number designation, area of collection, size, and sample weight are recorded. In samples without all fields complete, that information is currently unavailable.

Table 1 - Silicates

Mineral Name Group Designation Area Size Weight Augite Clinopyroxene 49-5858 <63μm 0.55g Olivine/Dunite Peridotite <63μm 0.52g Augite Clinopyroxene <63μm 0.50g Forsterite Olivine Pakistan <63μm 0.52g Diopside Clinopyroxene Ronda, Spain <63μm 0.52g Enstatite Orthopyroxene Ronda, Spain <63μm 0.56g Olivine Olivine <63μm 0.47g Fayalite/Magnetite Olivine/Spinel 49-1555 <63μm 0.52g Enstatite Pyroxene 49-2125 <63μm 0.50g Diopside Clinopyroxene Vesuve, Italy <63μm 0.55g

Table 2 - Sulfates

Name Group Designation Area Size Weight Kieserite <63μm 0.53g

Sample Preparation Minerals were obtained in either powdered form from the supplier or in bulk form as collected naturally. If collected in bulk form, the minerals were crushed using a mortar and pestle or other grinding equipment until a powdered form was obtained. The powdered forms were then filtered using a sieve and a vibrator plate. The sieve is a screen with hole sizes of 63 microns, so only particulates less than 63 µm were present in the final powder. This was the smallest sieve available. This particulate size was chosen to obtain better results from infrared spectroscopy. If the particulate matter is too large, the infrared light will reflect and refract from the sample in non-uniform ways, scattering the light and reducing the amount of information obtained by the collector. This will cause larger data scatter and inaccurate results in the collected spectra thus making proper characterization difficult. For actual missions, this preparation step may be able to be omitted, since the high surface temperatures will cause minerals to glow in the infrared naturally, which would allow the spectrometer to simply collect emitted light directly from the specimen under study. This will be explored in future studies.

For high temperature samples, this powdered form was then heated in a tube furnace. A tube furnace is a device with a ceramic cylindrical tube surrounded by resistive heating elements. The heating elements, which are enclosed in a ceramic layer of insulation, heat the

15 tube which in turn heats the sample inside. The tube surface can be regulated to reach a specific temperature, and the tube design allows free or directed gas exchange. The tube furnace was set to approximately 480°C to simulate temperature conditions on the Venusian surface. Samples were exposed to regular atmospheric air during heating. Samples were heated for 24 hours to allow any changes in composition or structure reasonable development time. Samples were then allowed to cool slowly to room temperature in air to prevent thermal shock and other effects that could interfere with measurement of heating effects.

Since water interferes with the spectra of mineral samples in the near infrared, NIR samples were measured only after heating. The samples were heated on a hot plate up to 150°C for two hours in a ceramic tube. This tube was connected to a gentle flow of nitrogen purge gas. This setup removed water from the sample so that false absorption bands would not show up in the recorded spectra.

To obtain better, more uniform results, a small metal drill bit with a flat end was used to level the surface of the powder in the tube.

Spectroscopy The prepared powders were analyzed using a Thermo Scientific Nicolet 6700 Fourier transform infrared spectrometer.

Nitrogen flow was used to purge the unregulated atmosphere from the machine. In standby mode (while a sample is not being tested), a constant flow level of 5 (per the unspecified flowmeter units) is maintained to the machine to prevent major interferences like condensation. During the first sample run, the flow level was set to 15 to ensure a good purge; in later samples, it was reduced to 10, which is a nominal flow value in the guidebook for the machine.

A probe-style emission/detection device was used to conduct the tests. The probe consists of multiple segments of fiber optic enclosed in a metallic sheath. One central segment of fiber transmits light from the source, and radial segments collect light after it is reflected from the sample. The use of a probe to collect sample data is comparable to a probe-setup that could be found on an actual Venusian exploration mission. A robotic arm with a fiber optic probe attached could easily sample multiple surface materials.

A calcium difluoride (CaF2) lens was used to split the source beam for the interferometer. The source used was white light. Backgrounds for near-infrared readings were taken using a titanium dioxide (TiO2) powder. A Thermo Electric Cooler (TEC) InGaAs 2.6 µm detector was used to collect reflected light. For initial scanning, 200 scans were taken at a resolution of 2 cm-1. For more thorough characterization, 300 scans were taken. A range of 4000 to 10000 cm-1 was used to limit extraneous data.

Data from the spectrometer was analyzed using OMNIC software. The raw data output of the spectrometer is in reflectance vs. wavenumber. To make the data more standardized and

16 meaningful, this was converted to reflectance vs. wavelength (µm). Wavelength is simply the inverse of wavenumber. The Omnic software was used to plot the resulting wavelength as discrete points using the default data point spacing of 0.005 micrometers. Reflectance was measured as a percentage of reflected light intensity as compared to the original source light.

Results and Discussion

Near-Infrared Results

Raw data output from the FTIR software is given in a percent reflectance versus wavenumber format. Percent reflectance is measured relative to the background, and wavenumber represents the inverse wavelength. This is converted to wavelength (in microns) in the figures below.

Unheated samples are samples that were minimally processed from the original source. They were crushed and filtered into a refined powder of known size, and they were heated for two hours at 150°C under nitrogen flow to remove water. This processing is not intense enough to change the spectra of the sample. Heated samples were those heated to 480°C in the tube furnace. They were also crushed and filtered into a refined powder of known size. Before collecting spectra, they were heated for two hours at 150°C under nitrogen flow as well to remove water.

Reflectance values were normalized to the maximum reflectance of the dataset, scaling the data. When spectra overlapped, a standard offset was used for one of the spectra across the dataset to shift the spectrum up; the shift is noted on the graphs, where applicable.

Since spectra were generated from 300 scans of the minerals, resulting features (or lack thereof) are of a relatively high degree of confidence. While the actual reflectance values may vary from standard sources, the difference between heated and unheated samples is much more important than actual values. Any systematic error would be present in all resulting spectra; since only the difference in the data is significant, these errors are easily subtracted. Additionally, the specific style of spectral feature is not necessarily dependent on the measured values; an absorption band is easily recognizable even if the slope of the spectra is slightly different between two between different spectra.

Unheated and Heated Near-Infrared Spectral Results - Olivine 1.40E+00 Unheated Offset of +0.2

1.20E+00

1.00E+00

8.00E-01

Unheated 6.00E-01

Heated % Reflectance%

4.00E-01

2.00E-01

0.00E+00 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 Wavelength (microns)

Figure 10 NIR-Olivine

Unheated and Heated Near-Infrared Spectral Results - Augite (clinopyroxene) 1.20E+00 Heated Offset of +0.1

1.00E+00

8.00E-01

6.00E-01 Unheated

Heated % % Reflectance 4.00E-01

2.00E-01

0.00E+00 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 Wavelength (microns)

Figure 11 NIR-CPx3

Unheated and Heated Near-Infrared Spectral Results - Enstatite 1.20E+00 Heated Offset of +0.1

1.00E+00

8.00E-01

6.00E-01 Unheated

Heated % % Reflectance 4.00E-01

2.00E-01

0.00E+00 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 Wavelength (microns)

Figure 12 NIR - Enstatite

Unheated and Heated Near-Infrared Spectral Results - Olivine Forsterite 1.20E+00 Heated Offset of +0.1

1.00E+00

8.00E-01

6.00E-01 Unheated

Heated % % Reflectance 4.00E-01

2.00E-01

0.00E+00 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 Wavelength (microns)

Figure 13 NIR - Olivine Forsterite

Unheated and Heated Near-Infrared Spectral Results - Enstatite (orthopyroxene) 1.20E+00 Heated Offset of +0.1

1.00E+00

8.00E-01

6.00E-01 Unheated

Heated % % Reflectance 4.00E-01

2.00E-01

0.00E+00 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 Wavelength (microns)

Figure 14 NIR - OPx

In Figures 10-14, no reasonable difference is observed. This indicates that heating has no effect on the spectra of the sample. Any trapped gases or materials that would change the spectra during heating might have been lost during crushing and other processing. The activation energy for chemical processes might be higher than that reached by heating, making changes in chemical composition absent as well.

Figure 15 shows that kieserite exhibits a slight response in the lower end of the spectrum wavelength. This effect is seen as a flattening of the slope of the spectrum. This difference is quickly lost, though, and the resulting graphs again align. Slight differences in slope, though, are not enough to characterize large scale effects. More study on this specific mineral could be warranted to further explore this effect, but since it does not affect identification in any way, those studies are not pursued here.

Unheated and Heated Near-Infrared Spectral Results - Kieserite 1.20E+00 Heated Offset of +0.1

1.00E+00

8.00E-01

6.00E-01 Unheated

Heated % % Reflectance 4.00E-01

2.00E-01

0.00E+00 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 Wavelength (microns)

Figure 15 NIR - Kieserite

Figures 16 and 17 appear to show significant results for augite and olivine dunite. The spectra for unheated samples in both figures do not appear to be characteristic of the minerals. The lack of absorption bands and linear character indicate that an error is present in the data. This could be due to user error, software/data collection issues, or interference in the spectrometer. Heated results, though, are characteristic of mineral spectra and again do not appear to show a meaningful difference from expected results.

Unheated and Heated Near-Infrared Spectral Results - Augite 1.20E+00

1.00E+00

8.00E-01

6.00E-01 Unheated

Heated % % Reflectance 4.00E-01

2.00E-01

0.00E+00 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 Wavelength (microns)

Figure 16 NIR - Augite

Unheated and Heated Near-Infrared Spectral Results - Olivine Dunite 1.20E+00

1.00E+00

8.00E-01

6.00E-01 Unheated

Heated % % Reflectance 4.00E-01

2.00E-01

0.00E+00 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 Wavelength (microns)

Figure 17 NIR - Olivine Dunite

Conclusions

Through this project, a better foundation was developed for identification of mineralogy by Fourier transform infrared spectroscopy. This foundation will be useful as NASA and groups around the world begin to prepare for large-scale missions to the Venusian surface. Fourier transform infrared spectroscopy is an effective tool for mineral identification. As a simple, robust, and transportable means of spectroscopy, it will be particularly useful for the development of hardware to fly on future missions. Further studies will include observations on an in-situ measurement apparatus currently being designed. This apparatus will integrate a fiber optic probe with a tube furnace and gas flow equipment to take measurements at Venusian surface temperatures with appropriate atmospheric gases. This will help to characterize the exact spectral results that would be obtained on an actual mission. By comparing the work of this research with future results, differences between spectra taken in different conditions will be much more obvious. Through effective scientific preparations for future missions, future missions can continue building on the successes of the past while making new discoveries for the future.

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