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International audience; Results from the Sample Analysis at Mars (SAM)-evolved gas analyzer (EGA) on board the Mars Science Laboratory Curiosity rover constrained the alteration history and habitability potential of rocks sampled across the Siccar Point unconformity in Gale crater.The Glasgow member (Gm) mudstone just below the unconformity had evidence of acid sulfate or Si-poor brine alteration of Fe-smectite to Fe amorphous phases, leaching loss of Fe-Mg-sulfate and exchange of unfractionated sulfur 34S (δ34S=2±7‰) with enriched 34S (20±5‰, V-CDT). Carbon abundances did not significantly change (322-661 μgC/g) consistent with carbon stabilization by amorphous Al- and Fe-hydroxide phases. The Gm mudstone had no detectable oxychlorine and extremely low nitrate. Nitrate (0.06 wt.% NO3), oxychlorine (0.13 wt% ClO4), high C (1472 μg C/g), and low Fe/Mg-sulfate concentration (0.24 wt.% SO3) depleted in 34S (δ34S = -27‰ ± 7), were detected in the Stimson formation (Sf) eolian sandstone above the unconformity. Redox disequilibrium through the detections of iron sulfide and sulfate supported limited aqueous processes in the Sf sandstone. Si-poor brines or acidic fluids altered the Gm mudstone just below the unconformity but did not alter underlying Gm mudstones further from the contact. Chemical differences between the Sf and Gm rocks suggested that fluid interaction was minimal between the Sf and Gm rocks. These results suggested that the Gm rocks were altered by subsurface fluids after the Sf placement. Aqueous processes along the unconformity could have provided habitable conditions and in some cases, C and N levels could have supported heterotrophic microbial populations.

Mars Polar Science is an integrated, compelling system that serves as a nearby analogue to numerous other planets, supports human exploration, and habitability. Mars possesses the closest and most easily accessible layered ice deposits outside of Earth, and accessing those layers to read the climate record would be a triumph for planetary science.

The Sample Analysis at Mars instrument evolved gas analyzer (SAM-EGA) has detected evolved water, H2, SO2, H2S, NO, CO2, CO, O2 and HCl from two eolian sediments and nine sedimentary rocks from Gale Crater, Mars. These evolved gas detections indicate nitrates, organics, oxychlorine phase, and sulfates are widespread with phyllosilicates and carbonates occurring in select Gale Crater materials. Coevolved CO2 (160 ± 248 - 2373 ± 820 μgC(CO2)/g), and CO (11 ± 3 - 320 ± 130 μgC(CO)/g) suggest organic-C is present in Gale Crater materials. Five samples evolved CO2 at temperatures consistent with carbonate (0.32± 0.05 - 0.70± 0.1 wt.% CO3). Evolved NO amounts to 0.002 ± 0.007 - 0.06 ± 0.03 wt.% NO3. Evolution of O2 suggests oxychlorine phases (chlorate/perchlorate) (0.05 ± 0.025 - 1.05 ± 0.44wt. % ClO4) are present while SO2 evolution indicates the presence of crystalline and/or poorly crystalline Fe- and Mg-sulfate and possibly sulfide. Evolved H2O (0.9 ± 0.3 - 2.5 ± 1.6 wt.% H2O) is consistent with the presence of adsorbed water, hydrated salts, interlayer/structural water from phyllosilicates, and possible inclusion water in mineral/amorphous phases. Evolved H2 and H2S suggest reduced phases occur despite the presence of oxidized phases (nitrate, oxychlorine, sulfate, carbonate). SAM results coupled with CheMin mineralogical and APXS elemental analyses indicate that Gale Crater sedimentary rocks have experienced a complex authigenetic/diagenetic history involving fluids with varying pH, redox, and salt composition. The inferred geochemical conditions were favorable for microbial habitability and if life ever existed, there was likely sufficient organic-C to support a small microbial population.

Since landing at Gale crater, Mars, in August 2012, the Curiosity rover has searched for evidence of past habitability, such as organic compounds, which have proved elusive to previous missions. We report results from pyrolysis experiments by Curiosity’s Sample Analysis at Mars (SAM) instrument, focusing on the isotopic compositions of evolved CO2 and O2, which provide clues to the identities and origins of carbon- and oxygen-bearing phases in surface materials. We find that O2 is enriched in 18O (δ18O about 40‰). Its behaviour reflects the presence of oxychlorine compounds at the Martian surface, common to aeolian and sedimentary deposits. Peak temperatures and isotope ratios (δ18O from −61 ± 4‰ to 64 ± 7‰; δ13C from –25 ± 20‰ to 56 ± 11‰) of evolved CO2 indicate the presence of carbon in multiple phases. We suggest that some organic compounds reflect exogenous input from meteorites and interplanetary dust, while others could derive from in situ formation processes on Mars, such as abiotic photosynthesis or electrochemical reduction of CO2. The observed carbonate abundances could reflect a sink for about 425–640 millibar of atmospheric CO2, while an additional 100–170 millibar could be stored in oxalates formed at the surface. In addition, oxygen isotope ratios of putative carbonates suggest the possibility of widespread cryogenic carbonate formation during a previous era. The pyrolysis experiments of the SAM instrument on board the Curiosity rover reconstruct the origin of organics at Gale crater. Some of them come from meteorites, but others have been formed in situ, with widespread past formation of carbonates via cryogenesis. More than 0.5 bar of CO2 might have precipitated from the atmosphere.

© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. Variability in the sulfur isotopic composition in sediments can reflect atmospheric, geologic and biological processes. Evidence for ancient fluvio-lacustrine environments at Gale crater on Mars and a lack of efficient crustal recycling mechanisms on the planet suggests a surface environment that was once warm enough to allow the presence of liquid water, at least for discrete periods of time, and implies a greenhouse effect that may have been influenced by sulfur-bearing volcanic gases. Here we report in situ analyses of the sulfur isotopic compositions of SO2volatilized from ten sediment samples acquired by NASA's Curiosity rover along a 13 km traverse of Gale crater. We find large variations in sulfur isotopic composition that exceed those measured for Martian meteorites and show both depletion and enrichment in34S. Measured values of Δ34S range from - 47 ± 14‰ to 28 ± 7‰, similar to the range typical of terrestrial environments. Although limited geochronological constraints on the stratigraphy traversed by Curiosity are available, we propose that the observed sulfur isotopic signatures at Gale crater can be explained by equilibrium fractionation between sulfate and sulfide in an impact-driven hydrothermal system and atmospheric processing of sulfur-bearing gases during transient warm periods.

The deuterium-to-hydrogen (D/H) ratio in strongly bound water or hydroxyl groups in ancient martian clays retains the imprint of the water of formation of these minerals. Curiosity's Sample Analysis at Mars (SAM) experiment measured thermally evolved water and hydrogen gas released between 550° and 950°C from samples of Hesperian-era Gale crater smectite to determine this isotope ratio. The D/H value is 3.0 (±0.2) times the ratio in standard mean ocean water. The D/H ratio in this ~3-billion-year-old mudstone, which is half that of the present martian atmosphere but substantially higher than that expected in very early Mars, indicates an extended history of hydrogen escape and desiccation of the planet.

Polymorphisms in the gene encoding the glutathione S-transferase (GST) pi metabolizing enzyme have previously been associated with susceptibility to various cancers. In this study, the importance of GSTP1 genotypes as determinants of risk for oral cancer was assessed by examining the prevalence of GSTP1 alleles in 157 incident oral cancer cases and 260 non-cancer control individuals frequency-matched by race, sex, and age at diagnosis (+/- 5 years). The GSTP1*A, GSTP1*B, GSTP1*C, and GSTP1*D alleles were elucidated by polymerase chain reaction-restriction fragment length polymorphism analysis of polymorphisms present in codons 105 (isoleucine:valine) and 114 (alanine:valine) of the GSTP1 gene. Increased risk for oral cancer was observed in individuals who were homozygous for any combination of GSTP1 polymorphic alleles (i.e. *B, *C, and/or *D alleles; odds ratio = 2.4, 95% confidence interval = 1.2-4.8). Similar risk was observed in both Caucasians (odds ratio = 2.6, 95% confidence interval = 1.1-6.2) and African-Americans (odds ratio = 2.3, 95% CI = 0.68-7.5). A greater risk was observed in individuals with the GSTP1 (Var/Var) genotype who were exposed to low levels of smoking (i.e.or = 20 pack-years [py], odds ratio = 3.4, 95% confidence interval = 1.1-11) than among heavier smokers (i.e.20 pack-years [py], odds ratio = 1.4, 95% confidence interval = 0.48-4.0). These results suggest that GSTP1 genotype may play a role in risk for oral cancer particularly among lighter smokers.

The importance of both the CYP1A1 exon 7 (ile:val) and GSTM1 (0/0) polymorphisms in oral cancer susceptibility was assessed by examining polymorphic prevalences in 135 patients with oral cancer and 135 noncancer controls frequency-matched by age at diagnosis (+/- 5 years), race, sex, and institute of patient recruitment. The prevalence of the GSTM1 (0/0) genotype was approximately 51% in both cases and controls. The prevalence of the CYP1A1 (ile:val) polymorphism [including both the (ile/val) and (val/val) genotypes] was significantly higher in cases as compared to controls (17.6% versus 7.6%, respectively; crude odds ratio, 2.6; confidence interval, 1.2-5.7). No association was observed between polymorphic prevalence and levels of smoking or alcohol consumption in cases. These results suggest that the GSTM1 null genotype is not associated with oral cancer risk. These results also suggest that individuals with the CYP1A1 exon 7 ile:val polymorphism are at increased risk for oral cancer, and that this risk may not be influenced by differences in exposure to tobacco smoke.

The head-and-neck manifestations of HIV infection in children are very different from those in the adult population. Recurrent bacterial and viral infections are common manifestations, and persistent sinusitis or otitis media should make the otolaryngologist suspicious of HIV infection if the child has been exposed to the virus. Other common problems include mucocutaneous and esophageal candidiasis, recurrent herpes I and II and zoster infections, parotid swelling, and cervical lymphadeopathy.