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Analyses by the CheMin X-ray diffraction instrument on Mars Science Laboratory show that gypsum, bassanite, and anhydrite are common minerals at Gale crater. Warm conditions (∼6 to 30 °C) within CheMin drive gypsum dehydration to bassanite; measured surface temperatures and modeled temperature depth profiles indicate that near-equatorial warm-season surface heating can also cause gypsum dehydration to bassanite. By accounting for instrumental dehydration effects we are able to quantify the in situ abundances of Ca-sulfate phases in sedimentary rocks and in eolian sands at Gale crater. All three Ca-sulfate minerals occur together in some sedimentary rocks and their abundances and associations vary stratigraphically. Several Ca-sulfate diagenetic events are indicated. Salinity-driven anhydrite precipitation at temperatures below ∼50 °C may be supported by co-occurrence of more soluble salts. An alternative pathway to anhydrite via dehydration might be possible, but if so would likely be limited to warmer near-equatorial dark eolian sands that presently contain only anhydrite. The polyphase Ca-sulfate associations at Gale crater reflect limited opportunities for equilibration, and they presage mixed salt associations anticipated in higher strata that are more sulfate-rich and may mark local or global environmental change. Mineral transformations within CheMin also provide a better understanding of changes that might occur in samples returned from Mars.

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.

Crystal chemical algorithms were used to estimate the chemical composition of selected mineral phases observed with the CheMin X-ray diffractometer onboard the NASA Curiosity rover in Gale crater, Mars. The sampled materials include two wind-blown soils, Rocknest and Gobabeb, six mudstones in the Yellowknife Bay formation (John Klein and Cumberland) and the Murray formation (Confidence Hills, Mojave2, and Telegraph Peak), as well as five sandstones, Windjana and the samples of the unaltered Stimson formation (Big Sky and Okoruso) and the altered Stimson formation (Greenhorn and Lubango). The major mineral phases observed with the CheMin instrument in the Gale crater include plagioclase, sanidine, P21/c and C2/c clinopyroxene, orthopyroxene, olivine, spinel, and alunite-jarosite group minerals. The plagioclase analyzed with CheMin has an overall estimated average of An40(11) with a range of An30(8) to An63(6). The soil samples, Rocknest and Gobabeb, have an average of An56(8) while the Murray, Yellowknife Bay, unaltered Stimson, and altered Stimson formations have averages of An38(2), An37(5), An45(7), and An35(6), respectively. Alkali feldspar, specifically sanidine, average composition is Or74(17) with fully disordered Al/Si. Sanidine is most abundant in the Wind-jana sample (∼26 wt% of the crystalline material) and is fully disordered with a composition of Or87(5). The P21/c clinopyroxene pigeonite observed in Gale crater has a broad compositional range {[Mg0.95(12)-1.54(17)Fe0.18(17)-1.03(9)Ca0.00-0.28(6)]Σ2Si2O6} with an overall average of Mg1.18(19)Fe0.72(7)Ca0.10(9)Si2O6. The soils have the lowest Mg and highest Fe compositions [Mg0.95(5)Fe1.02(7)Ca0.03(4)Si2O6] of all of the Gale samples. Of the remaining samples, those of the Stimson formation exhibit the highest Mg and lowest Fe [average = Mg1.45(7)Fe0.35(13)Ca0.19(6)Si2O6]. Augite, C2/c clinopyroxene, is detected in just three samples, the soil samples [average = Mg0.92(5)Ca0.72(2)Fe0.36(5)Si2O6] and Windjana (Mg1.03(7)Ca0.75(4)Fe0.21(9)Si2O6). Orthopyroxene was not detected in the soil samples and has an overall average composition of Mg0.79(6)Fe1.20(6)Ca0.01(2)Si2O6 and a range of [Mg0.69(7)-0.86(20)Fe1.14(20)-1.31(7)Ca0.00-0.04(4)]Σ2Si2O6, with Big Sky exhibiting the lowest Mg content [Mg0.69(7)Fe1.31(7)Si2O6] and Okoruso exhibiting the highest [Mg0.86(20)Fe1.14(20)Si2O6]. Appreciable olivine was observed in only three of the Gale crater samples, the soils and Windjana. Assuming no Mn or Ca, the olivine has an average composition of Mg1.19(12)Fe0.81(12)SiO4 with a range of 1.08(3) to 1.45(7) Mg apfu. The soil samples [average = Mg1.11(4)Fe0.89SiO4] are significantly less magnesian than Windjana [Mg1.35(7)Fe0.65(7)SiO4]. We assume magnetite (Fe3O4) is cation-deficient (Fe3-x∎xO4) in Gale crater samples [average = Fe2.83(5)∎0.14O4; range 2.75(5) to 2.90(5) Fe apfu], but we also report other plausible cation substitutions such as Al, Mg, and Cr that would yield equivalent unit-cell parameters. Assuming cation-deficient magnetite, the Murray formation [average = Fe2.77(2)∎0.23O4] is noticeably more cation-deficient than the other Gale samples analyzed by CheMin. Note that despite the presence of Ti-rich magnetite in martian meteorites, the unit-cell parameters of Gale magnetite do not permit significant Ti substitution. Abundant jarosite is found in only one sample, Mojave2; its estimated composition is (K0.51(12)Na0.49)(Fe2.68(7)Al0.32)(SO4)2(OH)6. In addition to providing composition and abundances of the crystalline phases, we calculate the lower limit of the abundance of X-ray amorphous material and the composition thereof for each of the samples analyzed with CheMin. Each of the CheMin samples had a significant proportion of amorphous SiO2, except Windjana that has 3.6 wt% SiO2. Excluding Windjana, the amorphous materials have an SiO2 range of 24.1 to 75.9 wt% and an average of 47.6 wt%. Windjana has the highest FeOT (total Fe content calculated as FeO) at 43.1 wt%, but most of the CheMin samples also contain appreciable Fe, with an average of 16.8 wt%. With the exception of the altered Stimson formation samples, Greenhorn and Lubango, the majority of the observed SO3 is concentrated in the amorphous component (average = 11.6 wt%). Furthermore, we provide average amorphous-component compositions for the soils and the Mount Sharp group formations, as well as the limiting element for each CheMin sample.

The Mars 2020 mission will seek the signs of ancient life on Mars and will identify, prepare, document, and cache a set of samples for possible return to Earth by a follow-on mission. Mars 2020 and its Perseverance rover thus link and further two long-held goals in planetary science: a deep search for evidence of life in a habitable extraterrestrial environment, and the return of martian samples to Earth for analysis in terrestrial laboratories. The Mars 2020 spacecraft is based on the design of the highly successful Mars Science Laboratory and its Curiosity rover, but outfitted with a sophisticated suite of new science instruments. Ground-penetrating radar will illuminate geologic structures in the shallow subsurface, while a multi-faceted weather station will document martian environmental conditions. Several instruments can be used individually or in tandem to map the color, texture, chemistry, and mineralogy of rocks and regolith at the meter scale and at the submillimeter scale. The science instruments will be used to interpret the geology of the landing site, to identify habitable paleoenvironments, to seek ancient textural, elemental, mineralogical and organic biosignatures, and to locate and characterize the most promising samples for Earth return. Once selected, ∼35 samples of rock and regolith weighing about 15 grams each will be drilled directly into ultraclean and sterile sample tubes. Perseverance will also collect blank sample tubes to monitor the evolving rover contamination environment. In addition to its scientific instruments, Perseverance hosts technology demonstrations designed to facilitate future Mars exploration. These include a device to generate oxygen gas by electrolytic decomposition of atmospheric carbon dioxide, and a small helicopter to assess performance of a rotorcraft in the thin martian atmosphere. Mars 2020 entry, descent, and landing (EDL) will use the same approach that successfully delivered Curiosity to the martian surface, but with several new features that enable the spacecraft to land at previously inaccessible landing sites. A suite of cameras and a microphone will for the first time capture the sights and sounds of EDL. Mars 2020’s landing site was chosen to maximize scientific return of the mission for astrobiology and sample return. Several billion years ago Jezero crater held a 40 km diameter, few hundred-meter-deep lake, with both an inflow and an outflow channel. A prominent delta, fine-grained lacustrine sediments, and carbonate-bearing rocks offer attractive targets for habitability and for biosignature preservation potential. In addition, a possible volcanic unit in the crater and impact megabreccia in the crater rim, along with fluvially-deposited clasts derived from the large and lithologically diverse headwaters terrain, contribute substantially to the science value of the sample cache for investigations of the history of Mars and the Solar System. Even greater diversity, including very ancient aqueously altered rocks, is accessible in a notional rover traverse that ascends out of Jezero crater and explores the surrounding Nili Planum. Mars 2020 is conceived as the first element of a multi-mission Mars Sample Return campaign. After Mars 2020 has cached the samples, a follow-on mission consisting of a fetch rover and a rocket could retrieve and package them, and then launch the package into orbit. A third mission could capture the orbiting package and return it to Earth. To facilitate the sample handoff, Perseverance could deposit its collection of filled sample tubes in one or more locations, called depots, on the planet’s surface. Alternatively, if Perseverance remains functional, it could carry some or all the samples directly to the retrieval spacecraft. The Mars 2020 mission and its Perseverance rover launched from the Eastern Range at Cape Canaveral Air Force Station, Florida, on July 30, 2020. Landing at Jezero Crater will occur on Feb 18, 2021 at about 12:30 PM Pacific Time.

Establishing the presence and state of organic matter, including its possible biosignatures, in martian materials has been an elusive quest, despite limited reports of the existence of organic matter on Mars. We report the in situ detection of organic matter preserved in lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, Gale crater, by the Sample Analysis at Mars instrument suite onboard the Curiosity rover. Diverse pyrolysis products, including thiophenic, aromatic, and aliphatic compounds released at high temperatures (500° to 820°C), were directly detected by evolved gas analysis. Thiophenes were also observed by gas chromatography–mass spectrometry. Their presence suggests that sulfurization aided organic matter preservation. At least 50 nanomoles of organic carbon persists, probably as macromolecules containing 5% carbon as organic sulfur molecules.

The Curiosity rover has been sampling on Mars for the past 5 years (see the Perspective by ten Kate). Eigenbrode et al. used two instruments in the SAM (Sample Analysis at Mars) suite to catch traces of complex organics preserved in 3-billion-year-old sediments. Heating the sediments released an array of organics and volatiles reminiscent of organic-rich sedimentary rock found on Earth. Most methane on Earth is produced by biological sources, but numerous abiotic processes have been proposed to explain martian methane. Webster et al. report atmospheric measurements of methane covering 3 martian years and found that the background level varies with the local seasons. The seasonal variation provides an important clue for determining the origin of martian methane. Science , this issue p. 1096 , p. 1093 ; see also p. 1068 The background level of methane in Mars’ atmosphere varies with season, providing a clue to its origin. Variable levels of methane in the martian atmosphere have eluded explanation partly because the measurements are not repeatable in time or location. We report in situ measurements at Gale crater made over a 5-year period by the Tunable Laser Spectrometer on the Curiosity rover. The background levels of methane have a mean value 0.41 ± 0.16 parts per billion by volume (ppbv) (95% confidence interval) and exhibit a strong, repeatable seasonal variation (0.24 to 0.65 ppbv). This variation is greater than that predicted from either ultraviolet degradation of impact-delivered organics on the surface or from the annual surface pressure cycle. The large seasonal variation in the background and occurrences of higher temporary spikes (~7 ppbv) are consistent with small localized sources of methane released from martian surface or subsurface reservoirs.

The SuperCam instrument suite provides the Mars 2020 rover, Perseverance, with a number of versatile remote-sensing techniques that can be used at long distance as well as within the robotic-arm workspace. These include laser-induced breakdown spectroscopy (LIBS), remote time-resolved Raman and luminescence spectroscopies, and visible and infrared (VISIR; separately referred to as VIS and IR) reflectance spectroscopy. A remote micro-imager (RMI) provides high-resolution color context imaging, and a microphone can be used as a stand-alone tool for environmental studies or to determine physical properties of rocks and soils from shock waves of laser-produced plasmas. SuperCam is built in three parts: The mast unit (MU), consisting of the laser, telescope, RMI, IR spectrometer, and associated electronics, is described in a companion paper. The on-board calibration targets are described in another companion paper. Here we describe SuperCam’s body unit (BU) and testing of the integrated instrument. The BU, mounted inside the rover body, receives light from the MU via a 5.8 m optical fiber. The light is split into three wavelength bands by a demultiplexer, and is routed via fiber bundles to three optical spectrometers, two of which (UV and violet; 245–340 and 385–465 nm) are crossed Czerny-Turner reflection spectrometers, nearly identical to their counterparts on ChemCam. The third is a high-efficiency transmission spectrometer containing an optical intensifier capable of gating exposures to 100 ns or longer, with variable delay times relative to the laser pulse. This spectrometer covers 535–853 nm ( 105 – 7070 cm − 1 Raman shift relative to the 532 nm green laser beam) with 12 cm − 1 full-width at half-maximum peak resolution in the Raman fingerprint region. The BU electronics boards interface with the rover and control the instrument, returning data to the rover. Thermal systems maintain a warm temperature during cruise to Mars to avoid contamination on the optics, and cool the detectors during operations on Mars. Results obtained with the integrated instrument demonstrate its capabilities for LIBS, for which a library of 332 standards was developed. Examples of Raman and VISIR spectroscopy are shown, demonstrating clear mineral identification with both techniques. Luminescence spectra demonstrate the utility of having both spectral and temporal dimensions. Finally, RMI and microphone tests on the rover demonstrate the capabilities of these subsystems as well.

Mathematical relationships between unit-cell parameters and chemical composition were developed for selected mineral phases observed with the CheMin X-ray diffractometer onboard the Curiosity rover in Gale crater. This study presents algorithms for estimating the chemical composition of phases based solely on X-ray diffraction data. The mineral systems include plagioclase, alkali feldspar, Mg-Fe-Ca C2/c clinopyroxene, Mg-Fe-Ca P21/c clinopyroxene, Mg-Fe-Ca orthopyroxene, Mg-Fe olivine, magnetite, and other selected spinel oxides, and alunite-jarosite. These methods assume compositions of Na-Ca for plagioclase, K-Na for alkali feldspar, Mg-Fe-Ca for pyroxene, and Mg-Fe for olivine; however, some other minor elements may occur and their impact on measured unit-cell parameters is discussed. These crystal-chemical algorithms can be applied to material of any origin, whether that origin is Earth, Mars, an extraterrestrial body, or a laboratory.