Mastcam-Z is a multispectral, stereoscopic imaging investigation on the Mars 2020 mission’s Perseverance rover. Mastcam-Z consists of a pair of focusable, 4:1 zoomable cameras that provide broadband red/green/blue and narrowband 400-1000 nm color imaging with fields of view from 25.6° × 19.2° (26 mm focal length at 283 μrad/pixel) to 6.2° × 4.6° (110 mm focal length at 67.4 μrad/pixel). The cameras can resolve (≥ 5 pixels) ∼0.7 mm features at 2 m and ∼3.3 cm features at 100 m distance. Mastcam-Z shares significant heritage with the Mastcam instruments on the Mars Science Laboratory Curiosity rover. Each Mastcam-Z camera consists of zoom, focus, and filter wheel mechanisms and a 1648 × 1214 pixel charge-coupled device detector and electronics. The two Mastcam-Z cameras are mounted with a 24.4 cm stereo baseline and 2.3° total toe-in on a camera plate ∼2 m above the surface on the rover’s Remote Sensing Mast, which provides azimuth and elevation actuation. A separate digital electronics assembly inside the rover provides power, data processing and storage, and the interface to the rover computer. Primary and secondary Mastcam-Z calibration targets mounted on the rover top deck enable tactical reflectance calibration. Mastcam-Z multispectral, stereo, and panoramic images will be used to provide detailed morphology, topography, and geologic context along the rover’s traverse; constrain mineralogic, photometric, and physical properties of surface materials; monitor and characterize atmospheric and astronomical phenomena; and document the rover’s sample extraction and caching locations. Mastcam-Z images will also provide key engineering information to support sample selection and other rover driving and tool/instrument operations decisions.

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Abstract. The first thermal images of Phobos' shadow on the surface of Mars, in addition to simultaneous visible images, were obtained by the Phobos '88 Termoskan instrument. The best observed shadow occurrence was on the flanks of Arsia Mons. For this occurrence, we combined the observed decrease in visible illumination of the surface with the observed decrease in brightness temperature to calculate thermal inertias of the Martian surface. The most realistic of our three models of eclipse cooling improves upon our preliminary model by including nonisothermal initial conditions and downward atmospheric flux. Most of our derived inertias fall within the range 38 to 59 J m ': s 4n K 4 (0.9 to 1.4 10 -3 cal cm ': s 4a K4), corresponding to dust-sized particles (for a homogeneous surface), consistent with previous theories of Tharsis as a current area of dust deposition. Viking infrared thermal mapper (IRTM) inertias are diurnally derived and are sensitive to centimeter depths, whereas the shadow-derived inertias sample the upper tenths of a millimeter of the surface. The shadowderived inertias are lower than those derived from Viking IRTM measurements (84 to 147), however, uncertainties in both sets of derived inertias make conclusions about layering tenuous. Thus, near-surface millimeter versus centimeter layering may exist in this region, but if it does, it is likely not very significant. Both eclipse and diurnal inertias appear to increase near the eastern end of the shadow occurrence. We also analyzed a shadow occurrence near the crater Herschel that showed no observed cooling. This analysis was limited by cool morning temperatures and instrument sensitivity, but yielded a lower bound of 80 on eclipse inertias in that region. Based upon our results, we strongly recommend future spacecraft thermal observations of Phobos' shadow, and suggest that they will be most useful if they improve upon Termoskan's geographic and temporal coverage and its accuracy.

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Utilizing the Termoskan data set of the Phobos '88 mission we have recognized a new feature on Mars: ejecta blanket distinct in the thermal infrared (EDITH). Virtually all of the more than 100 features discovered in the Termoskan data are located on the plains near Valles Marineris. EDITHs have a startlingly clear dependence upon terrains of Hesperian age, implying a spatial or temporal dependence on Hesperian terrains. Almost no thermally distinct ejecta blankets are associated with any of the thousands of craters within the data set that occur on the older Noachian units. EDITHs also do not appear on the portions of the younger Tharsis Amazonian units seen in the data. The Hesperian terrain dependence cannot be explained by either atmospheric or impactor variations; Noachian and Hesperian terrains must have experienced identical atmospheric and impactor conditions during Hesperian times. Thermally distinct ejecta blankets therefore reflect target material differences and/or secondary modification processes. Not all lobate ejecta blankets are thermally distinct, but all EDITHs correlated with visibly discernible ejecta blankets are associated with lobate ejecta blankets. The boundaries of the thermally distinct areas usually follow closely the termini of the fluidized lobate ejecta blankets, even when the ejecta blankets show a high degree of sinuosity. Thus, the thermally distinct nature of EDITHs must be due to the primary ejecta formation process. The coupling of these thermal anomalies to morphology is unlike most sharp Martian inertia variations which are decoupled from observed surface morphology. Some thermally distinct ejecta blankets occur near otherwise similar craters that do not have thermally distinct ejecta blankets. Thus, wind patterns or locally available aeolian material cannot provide a single overall explanation for the observed variations. We compiled a data base of 110 EDITH and non-EDITH craters ranging in diameter from 4.2 km to 90.6 km. There are almost no correlations within the data base other than occurrence on Hesperian terrains. We postulate that most of the observed EDITHs are due to excavation of thermally distinctive Noachian age material from beneath a relatively thin layer of younger, more consolidated Hesperian volcanic material. The plausibility of this theory is supported by much geological evidence for relatively thin near-surface Hesperian deposits overlying massive Noachian megabreccias on the EDITH-rich plains units. We suggest that absence of thermally distinct ejecta blankets on Noachian and Amazonian terrains is due to absences of distinctive near-surface layering. Thermally distinct ejecta blankets are excellent locations for future landers and remote sensing •cause of relatively dust free surface exposures of material excavated from depth. . Laboratory experiments that vary atmospheric pressure and particle size have also reproduced some lobate crater morphologies Gault, 1979, 1984]. One of our motivations in studying Martian thermally distinct ejecta blankets in d...