An Examination of Soil Crusts on the Floor of Jezero Crater, Mars

Abstract

Martian soils are critically important for understanding the history of Mars, past potentially habitable environments, returned samples, and future human exploration. This paper examines soil crusts on the floor of Jezero crater encountered during initial phases of the Mars 2020 mission. Soil surface crusts have been observed on Mars at other locations, starting with the two Viking Lander missions. Rover observations show that soil crusts are also common across the floor of Jezero crater, revealed in 45 of 101 locations where rover wheels disturbed the soil surface, 2 out of 7 helicopter flights that crossed the wheel tracks, and 4 of 8 abrasion/drilling sites. Most soils measured by the SuperCam laser‐induced breakdown spectroscopy (LIBS) instrument show high hydrogen content at the surface, and fine‐grained soils also show a visible/near infrared (VISIR) 1.9 µm H2O absorption feature. The Planetary Instrument for X‐ray Lithochemistry (PIXL) and SuperCam observations suggest the presence of salts at the surface of rocks and soils. The correlation of S and Cl contents with H contents in SuperCam LIBS measurements suggests that the salts present are likely hydrated. On the “Naltsos” target, magnesium and sulfur are correlated in PIXL measurements, and Mg is tightly correlated with H at the SuperCam points, suggesting hydrated Mg‐sulfates. Mars Environmental Dynamics Analyzer (MEDA) observations indicate possible frost events and potential changes in the hydration of Mg‐sulfate salts. Jezero crater soil crusts may therefore form by salts that are hydrated by changes in relative humidity and frost events, cementing the soil surface together.

Evidence of Sulfate‐Rich Fluid Alteration in Jezero Crater Floor, Mars

“…In addition, this is consistent with the recent identification of starkeyite at Gale crater (Chipera et al, 2023). MEDA measurements of local temperature, humidity and pressures in Jezero crater at the time of collection of these data also confirm that starkeyite would most likely have been stable (Hausrath et al, 2023).…”

“…Sulfate minerals typically occur within Martian dust and soils (e.g., B. C. Clark & Van Hart, 1981; Kounaves et al., 2010; Wang, Haskin, et al., 2006); in light‐toned deposits present inside canyons, in chaos terrain, and within sedimentary rocks of Meridiani Planum (e.g., Ehlmann & Edwards, 2014; Gendrin et al., 2005; Wang et al., 2016); as evaporites or diagenetic precipitates in sedimentary rocks (e.g., McLennan et al., 2005; Rapin et al., 2019); and as mineralized veins that cross‐cut local stratigraphy (e.g., Kronyak et al., 2019; Nachon et al., 2014). In Jezero crater, sulfate phases have been detected in igneous units (Corpolongo et al., 2023; Mandon et al., 2023), regolith targets (Hausrath et al., 2023), and recently in the fan front (Hurowitz et al., 2023; Phua et al., 2023; Roppel et al., 2023). Sulfate minerals can hold water in two ways: (a) as part of the crystal structure in the case of hydrated sulfate phases, and (b) as fluid inclusions within sulfate crystals.…”

“…Sulfate, perchlorate, and chloride salts can extract water from (and release it to) the atmosphere under present‐day martian environmental conditions either by undergoing hydration, deliquescence, or by forming liquid brines (Gough et al., 2011; Martin‐Torres et al., 2015; Toner et al., 2016; Zorzano et al., 2009). Perseverance's instruments have detected the presence of hydrated Ca‐ and Mg‐sulfate minerals in Jezero crater rocks (Corpolongo et al., 2023; Mandon et al., 2023) and regolith targets (Hausrath et al., 2023). Observations by the Perseverance instrument Mars Environmental Dynamics Analyzer (MEDA) indicate the possibility of diurnal and seasonal changes in the hydration of Mg‐sulfate and Ca‐sulfate salts (Hausrath et al., 2023).…”

Diurnal Cycle of Rapid Air Temperature Fluctuations at Jezero Crater: Probability Distributions, Exponential Tails, Scaling, and Intermittency

“…The combination of environmental forcing through aeolian erosion, mechanical forcing from wind and pressure fluctuations, or thermodynamical forcing via changes in temperature and atmospheric composition, including water vapor, can cause a range of surface patterns. Some models that include environmental forcings from erosion and deposition represent them through a stochastic function that contains the statistical properties of environmental variability (e.g., Bosak et al., 2013; Cuerno et al., 2011; Grotzinger & Rothman, 1996; Hausrath et al., 2022).…”

Three‐Dimensional Data Preparation and Immersive Mission‐Spanning Visualization and Analysis of Mars 2020 Mastcam‐Z Stereo Image Sequences

“…Previous work on Mars has identified evidence of fractures in the soil surface that indicate the presence of crust in multiple locations site (e.g., Blake et al., 2013; Sullivan et al., 2008) indicating that this is a common phenomenon on Mars. The characteristics of the crust and extent of induration, as evidenced in the 3D observation of cracks and fractures, as well as tracks, sheds important light on the characteristics of the crust (Hausrath et al., 2023). The fractures indicate evidence of induration, which may also indicate the presence of hydration and salts.…”