On biosignatures for Mars

In this work, we address the difficulty of reliably identifying traces of life on Mars. Several independent lines of evidence are required to build a compelling body of proof. In particular, we underline the importance of correctly interpreting the geological and mineralogical context of the sites to be explored for the presence of biosignatures. We use as examples to illustrate this, ALH84001 (where knowledge of the geological context was very limited) and other terrestrial deposits, for which this could be properly established. We also discuss promising locations and formations to be explored by ongoing and future rover missions, including Oxia Planum, which, dated at 4.0 Ga, is the most ancient Mars location targeted for investigation yet

Characterizing Rock Abundance At ExoMars Landing Site Candidates

We present preliminary work to characterize surface rock abundance at ExoMars Rover landing site candidates. A challenge in quantifying the abundance of surface rocks is using the population of large (≳1 m) rocks that are resolved in orbital images to infer the size of the smaller, unresolved rock population. This is particularly relevant for the ExoMars Rover mission, where the Landing Module’s clearance of 35 cm makes it necessary to know the probability of encountering rocks where 0.35 < D < 1 m. ‘Float rocks’ are individual fragments of rock not associated with a continuous outcrop or body of rock —e.g. transported rocks or impact debris. These can be identified in Mars Reconnaissence Orbiter HiRISE images, where the mid-afternoon local solar time, dictated by MROs’ orbit, causes float rocks to appear as bright sunlit features adjacent to strong shadows. However, the smallest features resolvable in HiRISE images occupy around 3-4 pixels, corresponding to ~1-m sized rocks. This inherently limits the ability to directly identify from orbit the small, but potentially hazardous rock population. ‘Outcrop’ is defined as continuous expanses of bedrock or surficial deposits exposed at the surface. Both float rocks and outcrop can contribute to slopes that may constitute a hazard for landed missions. We present rock counts at ExoMars Rover landing site candidates and assess approaches to constrain the morphological characteristics of Mars’ surface that are relevant to rover and lander safety

Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover

The second ExoMars mission will be launched in 2020 to target an ancient location interpreted to have strong potential for past habitability and for preserving physical and chemical biosignatures (as well as abiotic/prebiotic organics). The mission will deliver a lander with instruments for atmospheric and geophysical investigations and a rover tasked with searching for signs of extinct life. The ExoMars rover will be equipped with a drill to collect material from outcrops and at depth down to 2 m. This subsurface sampling capability will provide the best chance yet to gain access to chemical biosignatures. Using the powerful Pasteur payload instruments, the ExoMars science team will conduct a holistic search for traces of life and seek corroborating geological context information. Key Words: Biosignatures—ExoMars—Landing sites—Mars rover—Search for life. Astrobiology 17, 471–510

Direct comparison of B-Type Natriuretic Peptide (BNP) and amino-terminal proBNP in a large population of patients with chronic and symptomatic heart failure: the Valsartan Heart Failure (Val-HeFT) data

Background: The B-type or brain natriuretic peptides (BNP) and the amino-terminal probrain natriuretic peptide (NT-proBNP) are good markers of prognosis and diagnosis in chronic heart failure (HF). It is unclear, however, whether differences in their biological characteristics modify their clinical correlates and prognostic performance in HF. This work aimed to provide a direct comparison of the prognostic value of BNP and NTproBNP in patients with chronic and stable HF. Methods: We measured BNP and NT-proBNP at baseline in 3916 patients enrolled in the Valsartan Heart Failure Trial. To identify the variables associated with both peptides, we conducted simple and multivariable linear regression analyses. We used Cox multivariable regression models to evaluate the independent prognostic value for all-cause mortality, mortality and morbidity, and hospitalization for HF. Prognostic performance was assessed by pairwise comparisons of the area under the curve of receiver-operator characteristic curves. Results: NT-proBNP and BNP had similar relationships with age, left ventrical ejection fraction, and internal diameter and creatinine clearance. Either peptide ranked as the first independent predictor of outcome after adjustment for major confounding clinical characteristics. ROC curves were almost superimposable for all-cause mortality (area under the curve (SE): BNP 0.665 (0.011) vs NT-proBNP 0.679 (0.011); P 0.0734), but NT-proBNP was superior to BNP for predicting mortality and morbidity (P 0.032) or hospitalization for HF (P 0.0143). Overall sensitivity and specificity ranged from 0.590 to 0.696. Conclusions: The natriuretic peptides BNP and NTproBNP showed subtle differences in their relation to clinical characteristics and prognostic performance in a large population of patients with chronic and stable HF. They were the most powerful independent markers of outcome in HF

2018 MAX-C/ExoMars Mission: The Orleans Mars-Analogue Rock Collection for Instrument Testing

International audienceIn order to reply to the exobiological goals of the 2018 MAX-C/ExoMars mission, the Orléans-OSUC analogue rock collection and database contains well characterised Mars analogue rocks and minerals for use in instrument testing and in situ missions

Testing the theory of immune selection in cancers that break the rules of transplantation

Modification of cancer cells likely to reduce their immunogenicity, including loss or down-regulation of MHC molecules, is now well documented and has become the main support for the concept of immune surveillance. The evidence that these modifications, in fact, result from selection by the immune system is less clear, since the possibility that they may result from reorganized metabolism associated with proliferation or from cell de-differentiation remains. Here, we (a) survey old and new transplantation experiments that test the possibility of selection and (b) survey how transmissible tumours of dogs and Tasmanian devils provide naturally evolved tests of immune surveillance

Strong Magnetic Field Fluctuations within Filamentary Auroral Density Cavities Interpreted as VLF Saucer Sources

The Geoelectrodynamics and Electro-Optical Detection of Electron and SuprathermalIon Currents (GEODESIC) sounding rocket encountered more than 100 filamentary densitycavities associated with enhanced plasma waves at ELF (3 kHz) and VLF (310 kHz)frequencies and at altitudes of 800990 km during an auroral substorm. These cavities weresimilar in size (20 m diameter in most cases) to so-called lower-hybrid cavities (LHCs)observed by previous sounding rockets and satellites; however, in contrast, many of theGEODESIC cavities exhibited up to tenfold enhancements in magnetic wave powerthroughout the VLF band. GEODESIC also observed enhancements of ELF and VLFelectric fields both parallel and perpendicular to the geomagnetic field B0 within cavities,though the VLF E field increases were often not as large proportionally as seen in themagnetic fields. This behavior is opposite to that predicted by previously published theoriesof LHCs based on passive scattering of externally incident auroral hiss. We argue thatthe GEODESIC cavities are active wave generation sites capable of radiating VLF wavesinto the surrounding plasma and producing VLF saucers, with energy supplied by cold,upward flowing electron beams composing the auroral return current. This interpretation issupported by the observation that the most intense waves, both inside and outside cavities,occurred in regions where energetic electron precipitation was largely inhibited orabsent altogether. We suggest that the wave-enhanced cavities encountered by GEODESICwere qualitatively different from those observed by earlier spacecraft because of thefortuitous timing of the GEODESIC launch, which placed the payload at apogee within asubstorm-related return current during its most intense phase, lasting only a few minutes

The Aeolian Environment of the Landing Site for the ExoMars Rosalind Franklin Rover in Oxia Planum, Mars

Aeolian features at Oxia Planum ‐ the 2023 landing site for the ExoMars Rosalind Franklin Rover (ERFR) ‐ are important for Mars exploration because they record information about past and current wind regimes, sand transport vectors, and lend insight to the abrasion, deposition, and transport of granular material. To characterize the wind regime and erosional history of Oxia Planum we used a combination of manual observational and machine‐learning techniques to analyze the morphometrics, distribution, and orientation of 10,753 aeolian bedforms (Transverse Aeolian Ridges; TARs) and landforms (Periodic Bedrock Ridges; PBRs) around the ERFR landing ellipses. We found that, irrespective of the scale of the TARs, crestline azimuths are consistent across the study area and we infer that the bedform forming winds blew from NW‐NNW towards SE‐SSE. PBR azimuths show a substantively different orientation to the aeolian bedforms, and we infer that the winds necessary to abrade PBRs had a N‐NNE or S‐SSE orientation (180° ambiguity). From observations of active dust devils and windstreaks from repeat imagery, we infer a W‐WNW or E‐ESE (180° ambiguity) wind dominates today. Finally, we compare the inferred wind direction results from the aeolian landscape to modelled wind data from Mars GCMs. We note that, despite landscape evidence to the contrary, modelled contemporary wind direction lacks the consistent directionality to be responsible for the orientation of aeolian features in Oxia Planum. These results characterize aeolian features ERFR will encounter and suggests multiple wind regimes have influenced the surficial expression of the landing site

Interleukin-6 gene amplification and shortened survival in glioblastoma patients

Interleukin-6 (IL-6) is known to promote tumour growth and survival. We evaluated IL-6 gene amplification in tumours from 53 glioma patients using fluorescence in situ hybridisation. Amplification events were detected only in glioblastomas (15 out of 36 cases), the most malignant tumours, and were significantly associated with decreased patient survival