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51. Mars exobiology landing sites for future exploration

Author

Landheim, Ragnhild, Greeley, Ronald, Desmarais, David, Farmer, Jack D, and Klein, Harold

Subjects
Lunar And Planetary Exploration
Abstract

The selection of landing sites for Exobiology is an important issue for planning for future Mars missions. Results of a recent site selection study which focused on potential landing sites described in the Mars Landing Site Catalog are presented. In addition, basic Exobiology science objectives in Mars exploration are reviewed, and the procedures used in site evaluation and prioritization are outlined.

Published
1993

52. The State and Future of Mars Polar Science and Exploration

Author

Clifford, Stephen M., Crisp, David, Fisher, David A., Herkenhoff, Ken E., Smrekar, Suzanne E., Thomas, Peter C., Wynn-Williams, David D., Zurek, Richard W., Barnes, Jeffrey R., Bills, Bruce G., Blake, Erik W., Calvin, Wendy M., Cameron, Jonathan M., Carr, Michael H., Christensen, Philip R., Clark, Benton C., Clow, Gary D., Cutts, James A., Dahl-Jensen, Dorthe, Durham, William B., Fanale, Fraser P., Farmer, Jack D., Forget, Francois, Gotto-Azuma, Kumiko, Grard, Rejean, Haberle, Robert M., Harrison, William, Harvey, Ralph, Howard, Alan D., Ingersoll, Andy P., James, Philip B., Kargel, Jeffrey S., Kieffer, Hugh H., Larsen, Janus, Lepper, Kenneth, Malin, Michael C., McCleese, Daniel J., Murray, Bruce, Nye, John F., Paige, David A., Platt, Stephen R., Plaut, Jeff J., Reeh, Niels, Rice, James W., Jr., Smith, David E., Stoker, Carol R., Tanaka, Kenneth L., Mosley-Thompson, Ellen, Thorsteinsson, Thorsteinn, Wood, Stephen E., Zent, Aaron, Zuber, Maria T., and Jay Zwally, H.

Published
2000
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54. Relationships between unit-cell parameters and composition for rock-forming minerals on Earth, Mars, and other extraterrestrial bodies

Author

Morrison, Shaunna M., primary, Downs, Robert T., additional, Blake, David F., additional, Prabhu, Anirudh, additional, Eleish, Ahmed, additional, Vaniman, David T., additional, Ming, Douglas W., additional, Rampe, Elizabeth B., additional, Hazen, Robert M., additional, Achilles, Cherie N., additional, Treiman, Allan H., additional, Yen, Albert S., additional, Morris, Richard V., additional, Bristow, Thomas F., additional, Chipera, Steve J., additional, Sarrazin, Philippe C., additional, Fendrich, Kim V., additional, Morookian, John Michael, additional, Farmer, Jack D., additional, Des Marais, David J., additional, and Craig, Patricia I., additional

Published
2018
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55. Crystal chemistry of martian minerals from Bradbury Landing through Naukluft Plateau, Gale crater, Mars

Author

Morrison, Shaunna M., primary, Downs, Robert T., additional, Blake, David F., additional, Vaniman, David T., additional, Ming, Douglas W., additional, Hazen, Robert M., additional, Treiman, Allan H., additional, Achilles, Cherie N., additional, Yen, Albert S., additional, Morris, Richard V., additional, Rampe, Elizabeth B., additional, Bristow, Thomas F., additional, Chipera, Steve J., additional, Sarrazin, Philippe C., additional, Gellert, Ralf, additional, Fendrich, Kim V., additional, Morookian, John Michael, additional, Farmer, Jack D., additional, Des Marais, David J., additional, and Craig, Patricia I., additional

Published
2018
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57. Mineralogy, provenance, and diagenesis of a potassic basaltic sandstone on Mars: CheMin X-ray diffraction of the Windjana sample (Kimberley area, Gale Crater): CHEMIN: WINDJANA

Author

Filiberto, Justin, Newcombe, Megan E., Morris, Richard V., Gupta, Sanjeev, Treiman, Allan H., Ming, Doug W., Gellert, Ralf, Bristow, Thomas F., Fendrich, Kim V., Rampe, Elizabeth B., Vasavada, Ashwin R., McAdam, Amy C., Chipera, Steve J., Vaniman, David T., Farmer, Jack D., Wiens, Roger C., Sumner, Dawn Y., Le Deit, Laetitia, Downs, Robert T., Schmidt, Mariek E., Bish, David L., Yen, Albert S., Rice, Melissa S., Morookian, John Michael, Baker, Michael B., Glazner, Allen F., Grotzinger, John P., Edgett, Kenneth S., Achilles, Cherie N., Stolper, Edward M., Spray, John G., Morrison, Shaunna M., Thompson, Lucy M., and Blake, David F.

Abstract

The Windjana drill sample, a sandstone of the Dillinger member (Kimberley formation, Gale Crater, Mars), was analyzed by CheMin X‐ray diffraction (XRD) in the MSL Curiosity rover. From Rietveld refinements of its XRD pattern, Windjana contains the following: sanidine (21% weight, ~Or95); augite (20%); magnetite (12%); pigeonite; olivine; plagioclase; amorphous and smectitic material (~25%); and percent levels of others including ilmenite, fluorapatite, and bassanite. From mass balance on the Alpha Proton X‐ray Spectrometer (APXS) chemical analysis, the amorphous material is Fe rich with nearly no other cations—like ferrihydrite. The Windjana sample shows little alteration and was likely cemented by its magnetite and ferrihydrite. From ChemCam Laser‐Induced Breakdown Spectrometer (LIBS) chemical analyses, Windjana is representative of the Dillinger and Mount Remarkable members of the Kimberley formation. LIBS data suggest that the Kimberley sediments include at least three chemical components. The most K‐rich targets have 5.6% K2O, ~1.8 times that of Windjana, implying a sediment component with >40% sanidine, e.g., a trachyte. A second component is rich in mafic minerals, with little feldspar (like a shergottite). A third component is richer in plagioclase and in Na2O, and is likely to be basaltic. The K‐rich sediment component is consistent with APXS and ChemCam observations of K‐rich rocks elsewhere in Gale Crater. The source of this sediment component was likely volcanic. The presence of sediment from many igneous sources, in concert with Curiosity's identifications of other igneous materials (e.g., mugearite), implies that the northern rim of Gale Crater exposes a diverse igneous complex, at least as diverse as that found in similar‐age terranes on Earth.

Published
2016
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59. Silicic volcanism on Mars evidenced by tridymite in high-SiO 2 sedimentary rock at Gale crater

Author

Morris, Richard V., primary, Vaniman, David T., additional, Blake, David F., additional, Gellert, Ralf, additional, Chipera, Steve J., additional, Rampe, Elizabeth B., additional, Ming, Douglas W., additional, Morrison, Shaunna M., additional, Downs, Robert T., additional, Treiman, Allan H., additional, Yen, Albert S., additional, Grotzinger, John P., additional, Achilles, Cherie N., additional, Bristow, Thomas F., additional, Crisp, Joy A., additional, Des Marais, David J., additional, Farmer, Jack D., additional, Fendrich, Kim V., additional, Frydenvang, Jens, additional, Graff, Trevor G., additional, Morookian, John-Michael, additional, Stolper, Edward M., additional, and Schwenzer, Susanne P., additional

Published
2016
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63. Report of the workshop for life detection in samples from Mars

Author

Kminek, Gerhard, primary, Conley, Catherine, additional, Allen, Carlton C., additional, Bartlett, Douglas H., additional, Beaty, David W., additional, Benning, Liane G., additional, Bhartia, Rohit, additional, Boston, Penelope J., additional, Duchaine, Caroline, additional, Farmer, Jack D., additional, Flynn, George J., additional, Glavin, Daniel P., additional, Gorby, Yuri, additional, Hallsworth, John E., additional, Mogul, Rakesh, additional, Moser, Duane, additional, Buford Price, P., additional, Pukall, Ruediger, additional, Fernandez-Remolar, David, additional, Smith, Caroline L., additional, Stedman, Ken, additional, Steele, Andrew, additional, Stepanauskas, Ramunas, additional, Sun, Henry, additional, Vago, Jorge L., additional, Voytek, Mary A., additional, Weiss, Paul S., additional, and Westall, Frances, additional

Published
2014
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66. Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater.

Author

Morris, Richard V., Vaniman, David T., Blake, David F., Gellert, Ralf, Chipera, Steve J., Rampe, Elizabeth B., Ming, Douglas W., Morrison, Shaunna M., Downs, Robert T., Treiman, Allan H., Yeni, Albert S., Grotzinger, John P., Achilles, Cherie N., Bristow, Thomas F., Crisp, Joy A., Des Marais, David J., Farmer, Jack D., Fendrich, Kim V., Frydenvang, Jens, and Graff, Trevor G.

Subjects
VOLCANISM, MARTIAN surface, SEDIMENTARY rocks, TRIDYMITE, CRISTOBALITE, GALE Crater (Mars)
Abstract

Tridymite, a low-pressure, high-temperature (>870 °C) SiO2 polymorph, was detected in a drill sample of laminated mudstone (Buckskin) at Marias Pass in Gale crater, Mars, by the Chemistry and Mineralogy X-ray diffraction instrument onboard the Mars Science Laboratory rover Curiosity. The tridymitic mudstone has ~40 wt.% crystalline and ~60 wt.% X-ray amorphous material and a bulk composition with ~74 wt.% SiO2 (Alpha Particle X-Ray Spectrometer analysis). Plagioclase (~17 wt.% of bulk sample), tridymite (~14 wt.%), sanidine (~3 wt.%), cation-deficient magnetite (~3 wt.%), cristobalite (~2 wt.%), and anhydrite (~1 wt.%) are the mudstone crystalline minerals. Amorphous material is silica-rich (~39 wt.% opal-A and/or high-SiO2 glass and opal-CT), volatile-bearing (16 wt.% mixed cation sulfates, phosphates, and chlorides−perchlorates−chlorates), and has minor TiO2 and Fe2O3T oxides (~5 wt.%). Rietveld refinement yielded a monoclinic structural model for a well-crystalline tridymite, consistent with high formation temperatures. Terrestrial tridymite is commonly associated with silicic volcanism, and detritus from such volcanism in a "Lake Gale" catchment environment can account for Buckskin's tridymite, cristobalite, feldspar, and any residual high-SiO2 glass. These cogenetic detrital phases are possibly sourced from the Gale crater wall/rim/central peak. Opaline silica could form during diagenesis from high-SiO2 glass, as amorphous precipitated silica, or as a residue of acidic leaching in the sediment source region or at Marias Pass. The amorphous mixed-cation salts and oxides and possibly the crystalline magnetite (otherwise detrital) are primary precipitates and/ or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions, temperatures, and acidities. Anhydrite is post lithification fracture/vein fill. [ABSTRACT FROM AUTHOR]

Published
2016
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67. Multispectral microimager for astrobiology

Author

Hoover, Richard B., Levin, Gilbert V., Rozanov, Alexei Y., Sellar, R. Glenn, Farmer, Jack D., Kieta, Andrew, Huang, Julie, Hoover, Richard B., Levin, Gilbert V., Rozanov, Alexei Y., Sellar, R. Glenn, Farmer, Jack D., Kieta, Andrew, and Huang, Julie

Abstract

A primary goal of the astrobiology program is the search for fossil records. The astrobiology exploration strategy calls for the location and return of samples indicative of environments conducive to life, and that best capture and preserve biomarkers. Successfully returning samples from environments conducive to life requires two primary capabilities: (1) in situ mapping of the mineralogy in order to determine whether the desired minerals are present; and (2) nondestructive screening of samples for additional in-situ testing and/or selection for return to laboratories for more in-depth examination. Two of the most powerful identification techniques are micro-imaging and visible/infrared spectroscopy. The design and test results are presented from a compact rugged instrument that combines micro-imaging and spectroscopic capability to provide in-situ analysis, mapping, and sample screening capabilities. Accurate reflectance spectra should be a measure of reflectance as a function of wavelength only. Other compact multispectral microimagers use separate LEDs (light-emitting diodes) for each wavelength and therefore vary the angles of illumination when changing wavelengths. When observing a specularly-reflecting sample, this produces grossly inaccurate spectra due to the variation in the angle of illumination. An advanced design and test results are presented for a multispectral microimager which demonstrates two key advances relative to previous LED-based microimagers: (i) acquisition of actual reflectance spectra in which the flux is a function of wavelength only, rather than a function of both wavelength and illumination geometry; and (ii) increase in the number of spectral bands to eight bands covering a spectral range of 468 to 975 nm.

Published
2006

68. Mauna Kea, Hawaii, as an Analog Site for Future Planetary Resource Exploration: Results from the 2010 ILSO-ISRU Field-Testing Campaign

Author

ten Kate, Inge L., primary, Armstrong, Rob, additional, Bernhardt, Bodo, additional, Blumers, Mathias, additional, Craft, Jack, additional, Boucher, Dale, additional, Caillibot, Eric, additional, Captain, Janine, additional, Deleuterio, Gabriele, additional, Farmer, Jack D., additional, Glavin, Daniel P., additional, Graff, Trevor, additional, Hamilton, John C., additional, Klingelhöfer, Göstar, additional, Morris, Richard V., additional, Nuñez, Jorge I., additional, Quinn, Jacqueline W., additional, Sanders, Gerald B., additional, Sellar, R. Glenn, additional, Sigurdson, Leanne, additional, Taylor, Ross, additional, and Zacny, Kris, additional

Published
2013
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70. Characteristics, distribution, origin, and significance of opaline silica observed by the Spirit rover in Gusev crater, Mars

Author

Ruff, Steven W., primary, Farmer, Jack D., additional, Calvin, Wendy M., additional, Herkenhoff, Kenneth E., additional, Johnson, Jeffrey R., additional, Morris, Richard V., additional, Rice, Melissa S., additional, Arvidson, Raymond E., additional, Bell, James F., additional, Christensen, Philip R., additional, and Squyres, Steven W., additional

Published
2011
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73. The NASA Astrobiology Roadmap

Author

Des Marais, David J., primary, Nuth, Joseph A., additional, Allamandola, Louis J., additional, Boss, Alan P., additional, Farmer, Jack D., additional, Hoehler, Tori M., additional, Jakosky, Bruce M., additional, Meadows, Victoria S., additional, Pohorille, Andrew, additional, Runnegar, Bruce, additional, and Spormann, Alfred M., additional

Published
2008
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75. Metagenome-based diversity analyses suggest a significant contribution of non-cyanobacterial lineages to carbonate precipitation in modern microbialites.

Author

Saghaï, Aurélien, Zivanovic, Yvan, Zeyen, Nina, Moreira, David, Benzerara, Karim, Deschamps, Philippe, Bertolino, Paola, Ragon, Marie, Tavera, Rosaluz, López-Archilla, Ana I., López-García, Purificación, Swingley, Wesley Douglas, and Farmer, Jack D.

Subjects
METAGENOMICS, BACTERIAL diversity, CARBONATES
Abstract

Cyanobacteria are thought to play a key role in carbonate formation due to their metabolic activity, but other organisms carrying out oxygenic photosynthesis (photosynthetic eukaryotes) or other metabolisms (e.g., anoxygenic photosynthesis, sulfate reduction), may also contribute to carbonate formation. To obtain more quantitative information than that provided by more classical PCR-dependent methods, we studied the microbial diversity of microbialites from the Alchichica crater lake (Mexico) by mining for 16S/18S rRNA genes in metagenomes obtained by direct sequencing of environmental DNA. We studied samples collected at the Western (AL-W) and Northern (AL-N) shores of the lake and, at the latter site, along a depth gradient (1, 5, 10, and 15 m depth). The associated microbial communities were mainly composed of bacteria, most of which seemed heterotrophic, whereas archaea were negligible. Eukaryotes composed a relatively minor fraction dominated by photosynthetic lineages, diatoms in AL-W, influenced by Si-rich seepage waters, and green algae in AL-N samples. Members of the Gammaproteobacteria and Alphaproteobacteria classes of Proteobacteria, Cyanobacteria, and Bacteroidetes were the most abundant bacterial taxa, followed by Planctomycetes, Deltaproteobacteria (Proteobacteria), Verrucomicrobia, Actinobacteria, Firmicutes, and Chloroflexi. Community composition varied among sites and with depth. Although cyanobacteria were the most important bacterial group contributing to the carbonate precipitation potential, photosynthetic eukaryotes, anoxygenic photosynthesizers and sulfate reducers were also very abundant. Cyanobacteria affiliated to Pleurocapsales largely increased with depth. Scanning electron microscopy (SEM) observations showed considerable areas of aragonite-encrusted Pleurocapsa-like cyanobacteria at microscale. Multivariate statistical analyses showed a strong positive correlation of Pleurocapsales and Chroococcales with aragonite formation at macroscale, and suggest a potential causal link. Despite the previous identification of intracellularly calcifying cyanobacteria in Alchichica microbialites, most carbonate precipitation seems extracellular in this system. [ABSTRACT FROM AUTHOR]

Published
2015
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77. Key Science Questions from the Second Conference on Early Mars: Geologic, Hydrologic, and Climatic Evolution and the Implications for Life

Author

Beaty, David W., primary, Clifford, Stephen M., additional, Borg, Lars E., additional, Catling, David C., additional, Craddock, Robert A., additional, Marais, David J. Des, additional, Farmer, Jack D., additional, Frey, Herbert V., additional, Haberle, Robert M., additional, Mckay, Christopher P., additional, Newsom, Horton E., additional, Parker, Timothy J., additional, Segura, Teresa, additional, and Tanaka, Kenneth L., additional

Published
2005
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78. An astrobiological perspective on Meridiani Planum

Author

Knoll, Andrew H., primary, Carr, Michael, additional, Clark, Benton, additional, Des Marais, David J., additional, Farmer, Jack D., additional, Fischer, Woodward W., additional, Grotzinger, John P., additional, McLennan, Scott M., additional, Malin, Michael, additional, Schröder, Christian, additional, Squyres, Steven, additional, Tosca, Nicholas J., additional, and Wdowiak, Thomas, additional

Published
2005
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83. Exploring Gusev Crater with Spirit: Review of science objectives and testable hypotheses

Author

Cabrol, Nathalie A., primary, Grin, Edmond A., additional, Carr, Michael H., additional, Sutter, Brad, additional, Moore, Jeffrey M., additional, Farmer, Jack D., additional, Greeley, Ronald, additional, Kuzmin, Ruslan O., additional, DesMarais, David J., additional, Kramer, Marc G., additional, Newsom, Horton, additional, Barber, Charles, additional, Thorsos, Ivan, additional, Tanaka, Kenneth L., additional, Barlow, Nadine G., additional, Fike, David A., additional, Urquhart, Mary L., additional, Grigsby, Brian, additional, Grant, Frederick D., additional, and de Goursac, Olivier, additional

Published
2003
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87. Fossil-hunting on Mars

Author

Farmer, Jack D.

Subjects
Mars (Planet) -- Discovery and exploration, Life -- Origin, Mineralogy, Determinative -- Research, Astronomy
Abstract

The identification of minerals such as calcium carbonate, silica and clay, which are all capable of entombing microorganisms, will provide information on the origin of life on the Earth and on Mars. Such minerals on earth have yielded fossilized microbes such as cyanobacteria and small organisms. The unfavorable atmosphere and surface conditions observed in Mars during the 20th century may have produced life 35 billion years ago, which may be extinct now and can be found as entombed fossils. Even if the entombed fossils are not found in the entombing minerals, the molecules inside such minerals will provide information on the early history of Mars and the origin of life on earth.

Published
1994

92. JET-SUSPENDED, CALCITE-BALLASTED CYANOBACTERIAL WATERWARTS IN A DESERT SPRING1.

Author

Garcia-Pichel, Ferran, Wade, Brian D, and Farmer, Jack D

Subjects
CYANOBACTERIA, CALCITE
Abstract

We describe a population of colonial cyanobacteria (waterwarts) that develops as the dominant primary producer in a bottom-fed, O2 -poor, warm spring in the Cuatro Ciénegas karstic region of the Mexican Chihuahuan Desert. The centimeter-sized waterwarts were suspended within a central, conically shaped, 6-m deep well by upwelling waters. Waterwarts were built by an Aphanothece -like unicellular cyanobacterium and supported a community of epiphytic filamentous cyanobacteria and diatoms but were free of heterotrophic bacteria inside. Sequence analysis of 16S rRNA genes revealed that this cyanobacterium is only distantly related to several strains of other unicellular cyanobacteria (Merismopedia, Cyanothece, Microcystis ). Waterwarts contained orderly arrangements of mineral crystallites, made up of microcrystalline low-magnesium calcite with high levels of strontium and sulfur. Waterwarts were 95.9% (v/v) glycan, 2.8% cells, and 1.3% mineral grains and had a buoyant density of 1.034 kg·L-1 . An analysis of the hydrological properties of the spring well and the waterwarts demonstrated that both large colony size and the presence of controlled amounts of mineral ballast are required to prevent the population from being washed out of the well. The unique hydrological characteristics of the spring have likely selected for both traits. The mechanisms by which controlled nucleation of extracellular calcite is achieved remain to be explored. [ABSTRACT FROM AUTHOR]

Published
2002
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94. Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater

Author

Morris, Richard V., Vaniman, David T., Blake, David F., Gellert, Ralf, Chipera, Steve J., Rampe, Elizabeth B., Ming, Douglas W., Morrison, Shaunna M., Downs, Robert T., Treiman, Allan H., Yen, Albert S., Grotzinger, John P., Achilles, Cherie N., Bristow, Thomas F., Crisp, Joy A., Des Marais, David J., Farmer, Jack D., Fendrich, Kim V., Frydenvang, Jens, Graff, Trevor G., Morookian, John-Michael, Stolper, Edward M., Schwenzer, Susanne P., Morris, Richard V., Vaniman, David T., Blake, David F., Gellert, Ralf, Chipera, Steve J., Rampe, Elizabeth B., Ming, Douglas W., Morrison, Shaunna M., Downs, Robert T., Treiman, Allan H., Yen, Albert S., Grotzinger, John P., Achilles, Cherie N., Bristow, Thomas F., Crisp, Joy A., Des Marais, David J., Farmer, Jack D., Fendrich, Kim V., Frydenvang, Jens, Graff, Trevor G., Morookian, John-Michael, Stolper, Edward M., and Schwenzer, Susanne P.

Abstract

Tridymite, a SiO2 mineral that crystallizes at low pressures and high temperatures (>870 °C) from high-SiO2 materials, was detected at high concentrations in a sedimentary mudstone in Gale crater, Mars. Mineralogy and abundance were determined by X-ray diffraction using the Chemistry and Mineralogy instrument on the Mars Science Laboratory rover Curiosity. Terrestrial tridymite is commonly associated with silicic volcanism where high temperatures and high-silica magmas prevail, so this occurrence is the first in situ mineralogical evidence for martian silicic volcanism. Multistep processes, including high-temperature alteration of silica-rich residues of acid sulfate leaching, are alternate formation pathways for martian tridymite but are less likely. The unexpected discovery of tridymite is further evidence of the complexity of igneous petrogenesis on Mars, with igneous evolution to high-SiO2 compositions.

95. Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater

Author

Morris, Richard V., Vaniman, David T., Blake, David F., Gellert, Ralf, Chipera, Steve J., Rampe, Elizabeth B., Ming, Douglas W., Morrison, Shaunna M., Downs, Robert T., Treiman, Allan H., Yen, Albert S., Grotzinger, John P., Achilles, Cherie N., Bristow, Thomas F., Crisp, Joy A., Des Marais, David J., Farmer, Jack D., Fendrich, Kim V., Frydenvang, Jens, Graff, Trevor G., Morookian, John-Michael, Stolper, Edward M., Schwenzer, Susanne P., Morris, Richard V., Vaniman, David T., Blake, David F., Gellert, Ralf, Chipera, Steve J., Rampe, Elizabeth B., Ming, Douglas W., Morrison, Shaunna M., Downs, Robert T., Treiman, Allan H., Yen, Albert S., Grotzinger, John P., Achilles, Cherie N., Bristow, Thomas F., Crisp, Joy A., Des Marais, David J., Farmer, Jack D., Fendrich, Kim V., Frydenvang, Jens, Graff, Trevor G., Morookian, John-Michael, Stolper, Edward M., and Schwenzer, Susanne P.

Abstract

Tridymite, a SiO2 mineral that crystallizes at low pressures and high temperatures (>870 °C) from high-SiO2 materials, was detected at high concentrations in a sedimentary mudstone in Gale crater, Mars. Mineralogy and abundance were determined by X-ray diffraction using the Chemistry and Mineralogy instrument on the Mars Science Laboratory rover Curiosity. Terrestrial tridymite is commonly associated with silicic volcanism where high temperatures and high-silica magmas prevail, so this occurrence is the first in situ mineralogical evidence for martian silicic volcanism. Multistep processes, including high-temperature alteration of silica-rich residues of acid sulfate leaching, are alternate formation pathways for martian tridymite but are less likely. The unexpected discovery of tridymite is further evidence of the complexity of igneous petrogenesis on Mars, with igneous evolution to high-SiO2 compositions.

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