| 1. |
- Cousin, A., et al.
(författare)
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Compositions of coarse and fine particles in martian soils at gale: A window into the production of soils
- 2015
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Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 249, s. 22-42
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Tidskriftsartikel (refereegranskat)abstract
- The ChemCam instrument onboard the Curiosity rover provides for the first time an opportunity to study martian soils at a sub-millimeter resolution. In this work, we analyzed 24 soil targets probed by ChemCam during the first 250 sols on Mars. Using the depth profile capability of the ChemCam LIBS (Laser-Induced Breakdown Spectroscopy) technique, we found that 45% of the soils contained coarse grains (>500 μm). Three distinct clusters have been detected: Cluster 1 shows a low SiO2 content; Cluster 2 corresponds to coarse grains with a felsic composition, whereas Cluster 3 presents a typical basaltic composition. Coarse grains from Cluster 2 have been mostly observed exposed in the vicinity of the landing site, whereas coarse grains from Clusters 1 and 3 have been detected mostly buried, and were found all along the rover traverse. The possible origin of these coarse grains was investigated. Felsic (Cluster 2) coarse grains have the same origin as the felsic rocks encountered near the landing site, whereas the origin of the coarse grains from Clusters 1 and 3 seems to be more global. Fine-grained soils (particle size < laser beam diameter which is between 300 and 500 μm) show a homogeneous composition all along the traverse, different from the composition of the rocks encountered at Gale. Although they contain a certain amount of hydrated amorphous component depleted in SiO2, possibly present as a surface coating, their overall chemical homogeneity and their close-to-basaltic composition suggest limited, or isochemical alteration, and a limited interaction with liquid water. Fine particles and coarse grains from Cluster 1 have a similar composition, and the former could derive from weathering of the latter. Overall martian soils have a bulk composition between that of fine particles and coarse grains. This work shows that the ChemCam instrument provides a means to study the variability of soil composition at a scale not achievable by bulk chemical analyses.
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| 2. |
- Mangold, N., et al.
(författare)
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Perseverance rover reveals an ancient delta-lake system and flood deposits at Jezero crater, Mars
- 2021
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 374:6568
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Tidskriftsartikel (refereegranskat)abstract
- Observations from orbital spacecraft have shown that Jezero crater on Mars contains a prominent fan-shaped body of sedimentary rock deposited at its western margin. The Perseverance rover landed in Jezero crater in February 2021. We analyze images taken by the rover in the 3 months after landing. The fan has outcrop faces, which were invisible from orbit, that record the hydrological evolution of Jezero crater. We interpret the presence of inclined strata in these outcrops as evidence of deltas that advanced into a lake. In contrast, the uppermost fan strata are composed of boulder conglomerates, which imply deposition by episodic high-energy floods. This sedimentary succession indicates a transition from sustained hydrologic activity in a persistent lake environment to highly energetic short-duration fluvial flows.
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| 3. |
- McLennan, S.M., et al.
(författare)
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Elemental Geochemistry of Sedimentary Rocks at Yellowknife Bay, Gale Crater, Mars
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6169
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Tidskriftsartikel (refereegranskat)abstract
- Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine–rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.
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