Abstract. The Curiosity rover discovered fine--grained sedimentary rocks, inferred to represent an ancient lake, preserve evidence of an environment that would have been suited to support a Martian biosphere founded on chemolithoautotrophy. This aqueous environment was characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species. C, H, O, S, N, and P were measured directly as key biogenic elements, and by inference N and P are assumed to have been available. The environment likely had a minimum duration of hundreds to tens of thousands of years. These results highlight the biological viability of fluvial--lacustrine environments in the post--Noachian history of Mars.

X-ray diffraction analysis of the Rocknest scoop sample is described in (23); similar analyses were performed for John Klein and Cumberland. John Klein and Cumberland were the first two drill samples collected by Curiosity. All scooped or drilled samples pass through the Collection and Handling for In situ Martian Rock Analysis (CHIMRA) sample collection and processing system (10). All powders for X-ray diffraction are processed through a 150-m sieve before delivering a portion to the CheMin inlet funnel.The sieved drill powders were placed into sample cells with 6 μm thick Mylar® windows. Mylar® contributes a minor, broad scattering signature in diffraction patterns that is generally "swamped" by diffraction from the loaded sample. In addition, an aluminized light shield also contributes "peaks" to the observed diffraction patterns. Only ~10 mm 3 of material is required to fill the active volume of the sample cell, which is a disc-shaped volume 8 mm in diameter and 175 m thick. A collimated ∼70 μm diameter X-ray beam illuminates the center of the sample cell. A piezoelectric vibration system on each cell pair shakes the material during analysis, causing grains in the cell to pass through the X-ray beam in random orientations.CheMin measures XRD and XRF data simultaneously using Co radiation in transmission geometry (11). The instrument operates in single-photon counting mode so that between each readout the majority of CCD pixels are struck by either a single X-ray photon or by no photons. In this way, the system can determine both the energy of the photons striking the CCD (XRF) and the two-dimensional (2-D) position of each photon (XRD). The energy and positional information of detected photons in each frame are summed over repeated 10-sec measurements into a "minor frame" of 30 min of data (180 frames). The 2-D distribution of Co K X-ray intensity represents the XRD pattern of the sample. Circumferential integration of these rings, corrected for arc length, produces a conventional 1-D XRD pattern. For conversion of the 2-D CCD pattern to a 1-D pattern we have used FilmScan © software from Materials Data, Inc.CheMin generally operates for only a few hours each night, when the CCD can be cooled to its lowest temperature, collecting as many minor frames as possible for the available analysis time, usually five to seven per night. XRD data were acquired over multiple nights for the John Klein and Cumberland drill samples to provide acceptable counting statistics. Total data collection times were 33.9 hr for John Klein and 20.2 hr for Cumberland. The data for individual minor frames and for each night's analysis were examined separately, and there was no evidence of any changes in instrumental parameters as a function of time over the duration of these analyses. Before sample delivery and analysis, the empty cell was analyzed to confirm that it was indeed empty before receiving the sample. The flight instrument was calibrated on the ground before flight using a quartz-beryl standard, and measurement of this st...

Samples and Methods 1.1. Starting Materials The starting materials for this study were selected from various hydrous lithospheric veins from the French Pyrenees (sampling localities: Etang de Lherz, Castillon-en-Couserans, Argein, Espeche and Avezac) (S1, S2). The hornblendite, AG4, and clinopyroxene (cpx)-hornblendite, AG7, were selected base on the fact that their amphibole compositions are characteristic of those found in metasomatic veins worldwide (Fig. 2 and S2). As we discuss in the main article, we do not think that individual veins are representative of lowdegree partial melts of mantle peridotite (± volatiles); i.e., vein compositions do not represent liquid compositions. Instead, the veins are the "cumulate" residues produced by fractional crystallization of low-degree mantle melts as they ascend and cool within the lithosphere. Depending on pressure and liquid volatile content, such a process may well generate a continuum from anhydrous to hydrous phase assemblages (S3-S6). Figure S3 shows that while the whole-rock compositions of various Pyrenean amphibole-bearing veins cover a large range, the compositions of the amphiboles within the veins are much more restricted in composition. Thus, the bulk-rock vein compositions reflect the modal abundance of amphibole relative to nominally anhydrous minerals, e.g., amphibole (amph) + minor Fe-Ti oxides for AG2 and 4, cpx + amph for AG7, and cpx + olivine (ol) + amph for AG6 and 1, rather than the bulk composition of any basanitic liquid. Another important point to stress is that the compositions of amphiboles from Pyrenean metasomatic veins are similar to the compositions of amphiboles that crystallize from ne-normative (S7) to hy-normative (S8) experimental liquids (Fig. S3). This suggests that the amphibole in our starting Fig. S1. Major-element oxides or oxides ratios vs. SiO 2 or MgO (volatile-free) in the partial melts of AG4 and AG7 (this study), and silica-deficient gt pyroxenites either with (S39) or without CO 2 (S40, S41) relative to continental and oceanic intraplate basalt and MORB compositions; (A) CaO/Al 2 O 3 vs. SiO 2 , (B) Al 2 O 3 / TiO 2 vs. SiO 2 , (C) Na 2 O vs. SiO 2 , (D) Al 2 O 3 vs. MgO, (E) CaO vs. MgO, and (F) CaO/Al2O3 vs. MgO. Filled grey circles: OIBs; filled black circles: continental intraplate basalts; filled white circles: MORBs (all rock compositions from GEOROC and PetDB databases; plotted rocks have 8-15 wt. % MgO in panel A to C and have SiO 2 wt. % below 52 in panel D to F). Filled dark blue triangles: glass compositions from 2-5 GPa experiments on silica-deficient gt pyroxenites (open dark blue triangle is the starting composition) (S40, S41). Filled light blue triangles: glass compositions from 3 GPa experiments on silica-deficient gt pyroxenites with 5 wt. % CO 2 (open light blue triangle is the starting composition) (S39). Filled red diamonds: hornblendite AG4 melts (open red diamond: starting material). Filled green diamonds: clinopyroxene hornblendite AG7 melts (open green diamond: starting material). Orange filled...

International audienceSamples from the Rocknest aeolian deposit were heated to ~835°C under helium flow and evolved gases analyzed by Curiosity's Sample Analysis at Mars instrument suite. H2O, SO2, CO2, and O2 were the major gases released. Water abundance (1.5 to 3 weight percent) and release temperature suggest that H2O is bound within an amorphous component of the sample. Decomposition of fine-grained Fe or Mg carbonate is the likely source of much of the evolved CO2. Evolved O2 is coincident with the release of Cl, suggesting that oxygen is produced from thermal decomposition of an oxychloride compound. Elevated δD values are consistent with recent atmospheric exchange. Carbon isotopes indicate multiple carbon sources in the fines. Several simple organic compounds were detected, but they are not definitively martian in origin

The Radiation Assessment Detector (RAD) on the Mars Science Laboratory's Curiosity rover began making detailed measurements of the cosmic ray and energetic particle radiation environment on the surface of Mars on 7 August 2012. We report and discuss measurements of the absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum. These measurements provide insight into the radiation hazards associated with a human mission to the surface of Mars, and provide an anchor point to model the subsurface radiation environment, with implications for microbial survival times of any possible extant or past life, as well as for the preservation of potential organic biosignatures of the ancient Martian environment.