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statistics in space


environments that would support life as it is currently understood on Earth’, with a particular emphasis on ‘H2


0, water-formed


minerals, and organic molecules’. The presence or absence of water is not only of scientific interest to archaeoexobiologists; it is also of crucial interest to any plans for colonisation, manned exploration, or economic exploitation. A main focus of Curiosity’s studies will be carbonate minerals (which form in the presence of free water) and the puzzle around shifting pH levels over time. Thanks to the tight laser beam and the


small volumes of material ablated, Curiosity’s LIBS technique has a high resolution that allows sampling at the individual mineral grain level. This yields high-quality data sets, but also high data volumes as numerous samples build up to provide an overview of bulk composition. Starting from terrestrial experiments conducted under simulated Martian conditions, a principle components analysis of spectra (in Camo Software’s Unscrambler X) reduces the thousands of variables involved. A manageable number of categories results, against which rocks scanned on Mars can be classified. Multiple regression models, applied to concentrations of elements in the samples, allow identification of unknown materials. Concentration on carbonates has not


come out of the blue, nor as a shot in the dark. They feature in ancient Martian meteorites, and deposits have already been identified[2]


by analysis of data gathered


by Spirit, one of Curiosity’s predecessor rovers. On a macro scale, water shapes landscapes and there is evidence in Martian geomorphology to suggest large quantities of moving surface water in the past – most spectacularly the immense Ma’adim Vallis flow channel, which runs into Gusev crater. For this latter reason, there is a lot of interest in the Martian gully systems[3, 4]


in general. As with all extraterrestrial geology,


maximum use of analytic induction has to compensate for ease of access, with maximum information squeezed from limited data. Good use has to be made of analogous research on Earth to provide frameworks, against which targeted remote data collection can be assessed. Rovers, though they can surmount quite large obstacles, are happiest on relatively flat surfaces, which rules out direct physical exploration of the steep terrains that accompany water courses. This, in turn, means that ways must be sought to secure collateral data, which can shed indirect analytic light on the true foci of interest.


www.scientific-computing.com


Mössbauer (MB) spectra and Mini-Thermal- Emission Spectra (Mini-TES) derived from analysis of Spirit rover data gathered in the Gusev crater on Mars. From Morris et al[2]


Spirit went into Gusev in the hope of discovering stratified rocks that could be sampled for data that might analytically illuminate the nature of the upstream canyon, but found instead an igneous surface. This is assumed to be a later volcanic flow over the sedimentary surface, but only further investigation can confirm or deny that supposition; Curiosity may or may not be able to improve the analytic picture.


expansion and contraction of ice close below the surface. As always, data analysis is not proving anything here; but it does provide the only means of assessing likelihoods upon which investigation leading to physical proof might profitably be based. If the mantle cracking ice hypothesis is correct, then its corollaries should link up with what we know of terrestrial sediment transport and permafrost structures, in ways that map onto the gully and delta formation patterns that we can observe on Mars. If that mapping appears to work, it will provide clear bases for productive exploration. Water, notwithstanding its importance, is


not the beginning and end of mineralogical interest and nor is Martian analysis separate from more general integrated understanding of our reachable neighbourhood. Papike et al, for instance, have conducted a comparative analytic study of planetary lithologies over two decades, the most recent fruit of which[8]


looks at differential levels of metallic sulphides. AS WITH ALL EXTRATERRESTRIAL GEOLOGY, MAXIMUM USE OF


ANALYTIC INDUCTION HAS TO COMPENSATE FOR EASE OF ACCESS, WITH MAXIMUM INFORMATION SQUEEZED FROM LIMITED DATA


The evidence is fairly strong that there


has been free water in considerable quantity during the history of Mars, but not where it has gone in the present. Primary hypotheses involve various combinations of loss into space and retention below the planetary surface and, once again, indirect data analytic deduction has to substitute for direct evidence. Data analytic interpretation of Martian argues for frozen desert


landforms[5-7]


conditions interspersed with short interludes in which ice sublimates, forms snow, and melts to water in local microclimates within the gullies. Central to this interpretation is a pattern of crack polygons which, if their analysis is correct, suggest thermal


Before moving from the Martian surface


to the asteroids, it’s worth looking at the transactions between them (of which, in fact, Papacy’s work is an example) and possible implications for the origins of life. Significant planetary impacts can come from a number of sources, including comets (such as Shoemaker-Levy 9, which hit Jupiter in 1994) and interstellar wanderers, but will more usually involve local asteroids. Material ejected by such an impact, if it is not reclaimed, will then become asteroidal in its turn; sometimes becoming part of the belt, other times following new orbits which, in time, intersect with those of other planets – Mars and Earth included. Back in the days when I was learning about Mother’s Jam Sandwiches, the idea that life might have arrived on earth from elsewhere was a daring science fiction concept breathlessly discussed behind the bike sheds. Nowadays it has a respectable following, and associated data analytic effort dedicated to its exploration. If there is anything to this exobiotic idea,


Sulfide Ni, Co, Cu, and Se concentrations based on EPMA and SXRF spot analyses for eight Martian meteorites and six lunar samples. From Papacy et al[8]


a microorganism must be (or, at least, have been) capable of surviving the extreme physical stresses involved in being almost instantaneously accelerated to escape velocity by impact of a large rock on its planetary habitat. A German study three years ago[9] studied this, subjecting populations of


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