The geological units on the floor of Jezero crater, Mars, are part of a wider regional stratigraphy of olivine-rich rocks, which extends well beyond the crater. We investigate the petrology of olivine and carbonate-bearing rocks of the Séítah formation in the floor of Jezero. Using multispectral images and x-ray fluorescence data, acquired by the Perseverance rover, we performed a petrographic analysis of the Bastide and Brac outcrops within this unit. We find that these outcrops are composed of igneous rock, moderately altered by aqueous fluid. The igneous rocks are mainly made of coarse-grained olivine, similar to some Martian meteorites. We interpret them as an olivine cumulate, formed by settling and enrichment of olivine through multi-stage cooling of a thick magma body.

Forty groups of subjects were given six lists of 25 nouns each for immediate free written recall. A measure of free recall was thereby obtained for each of 900 nouns in the Paivio, Yuille, and Madigan (1968) norms, each noun's measure based on the recall of 32 subjects. First-order correlations showed recall to be correlated with imagery, concreteness, meaningfulness, Thorndike-Lorge frequency, and Kucera-Francis frequency. Partial correlations showed meaningfulness to be essentially unrelated to recall and concreteness only moderately related. In contrast to previous comparisons, which were based on smaller ranges of frequency and were more susceptible to list-specific effects, imagery and frequency were found to be approximately equal in their influence on free recall.Presented with this report are measures of free recall for 900 of the 925 English nouns in the Paivio, Yuille, and Madigan (1968) norms. Several considerations led us to obtain these measures. The first was the general issue of which particular attributes of words affect free recall. It is well established in the Paivio et al. data that attributes suspected to influence recall are themselves correlated. Thus, if a relationship between a variable and recall performance is observed, it is important to establish that the effect is not due to contamination by other variables. Considerable effort has been spent along these lines and the influence of rated imagery on free recall seems firmly established (Postman, 1975). However, there are some recent complications with this picture (Richardson 1975a(Richardson , 1975b, and the roles of rated meaningfulness and frequency remain ambiguous. A second consideration was the issue of which variable has the greater influence on recall. Since Paivio's (l971) review there has been an increased acceptance of the view that rated imagery is more influential than meaningfulness and frequency. However, in contrast to the weight of evidence implicating the effect of rated imagery on free recall, the claim that imagery is more influential than frequency and meaningfulness is based on very few studies.Two more immediate concerns compelled the collection of these measures. The first was the outcome of an experiment by Warren (1977), who examined the effect of a pursuit-rotor task on recall by subjectsThe authors thank Patti Craig, Rena Dreskin, and Paige Highfield, who not only helped collect data, but also contributed to the research at other stages. We also thank M. Frank Evarts for his help with the unpublished study described in the introduction. Requests for reprints should be sent to Keith Clayton, 134 Wesley Hall, Department of Psychology, Vanderbilt University, Nashville, Tennessee 37240. engaged in recall and tracking concurrently. In two experiments Warren found that the recall-eoncurrent task interfered with picture recall but not word recall. This is consistent with the view that a concurrent tracking task interferes with, or suppresses, imagery during recall. If this is so, and if the superior recall of con...

Gale crater, the field site for NASA's Mars Science Laboratory Curiosity rover, contains a diverse and extensive record of aeolian deposition and erosion. This study focuses on a series of regularly spaced, curvilinear, and sometimes branching bedrock ridges that occur within the Glen Torridon region on the lower northwest flank of Aeolis Mons, the central mound within Gale crater. During Curiosity's exploration of Glen Torridon between sols ∼2300–3080, the rover drove through this field of ridges, providing the opportunity for in situ observation of these features. This study uses orbiter and rover data to characterize ridge morphology, spatial distribution, compositional and material properties, and association with other aeolian features in the area. Based on these observations, we find that the Glen Torridon ridges are consistent with an origin as wind‐eroded bedrock ridges, carved during the exhumation of Mount Sharp. Erosional features like the Glen Torridon ridges observed elsewhere on Mars, termed periodic bedrock ridges (PBRs), have been interpreted to form transverse to the dominant wind direction. The size and morphology of the Glen Torridon PBRs are consistent with transverse formative winds, but the orientation of nearby aeolian bedforms and bedrock erosional features raise the possibility of PBR formation by a net northeasterly wind regime. Although several formation models for the Glen Torridon PBRs are still under consideration, and questions persist about the nature of PBR‐forming paleowinds, the presence of PBRs at this site provides important constraints on the depositional and erosional history of Gale crater.

An important goal of remote sensing of planetary surfaces is to constrain the physical properties of surface materials. These physical properties, such as sorting or induration of loose sediments or the porosity and cementation of rock, are sensitive to the various physical processes, such as sedimentation, aeolian or fluvial transport, and volcanism, involved in the formation of surface materials, and as such provide clues to the geologic history of a region.Thermal Inertia (TI) is a summary parameter describing the thermophysical properties of a material, which is especially useful in that it can be derived from orbital temperature estimates using a thermal model (Section 2.1;

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.