* Astronomy

Title: Discovery of columnar jointing on Mars
Authors: M.P. Milazzo, L.P. Keszthelyi, W.L. Jaeger, M. Rosiek, S. Mattson, C. Verba, R.A. Beyer, P.E. Geissler, A.S. McEwen and the HiRISE Team

We report on the discovery of columnar jointing in Marte Valles, Mars. These columnar lavas were discovered in the wall of a pristine, 16-km-diameter impact crater and exhibit the features of terrestrial columnar basalts. There are discontinuous outcrops along the entire crater wall, suggesting that the columnar rocks covered a surface area of at least 200 km2, assuming that the rocks obliterated by the impact event were similarly jointed. We also see columns in the walls of other fresh craters in the nearby volcanic plains of Elysium Planitia - Amazonis Planitia, which include Marte Vallis, and in a well-preserved crater in northeast Hellas.

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The two Mars rovers, Spirit and Opportunity, have provided much information about the planet in the five years they've been rolling around the surface.
Most of the data relates to the central question of the role water might have played in the planet's past, and a new paper in Science, describing Opportunity's exploration of Victoria Crater in Meridiani Planum, a plain near the equator, is no exception.
The paper, by Steven W. Squyres, a Cornell astronomer, and more than 30 colleagues, summarises information that has been released over the past several years, and can itself be summarised in two words - wet and windy.

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Ed ~ er, three words

By combining data from several sources, Harry Y. (Hap) McSween (University of Tennessee), G. Jeffrey Taylor (University of Hawaii) and Michael B. Wyatt (Brown University) show that the surface of Mars is composed mostly of basalt not unlike those that make up the Earth's oceanic crust. McSween and his colleagues used data from Martian meteorites, analyses of soils and rocks at robotic landing sites, and chemical and mineralogical information from orbiting spacecraft. The data show that Mars is composed mostly of rocks similar to terrestrial basalts called tholeiites, which make up most oceanic islands, mid-ocean ridges, and the seafloor beneath sediments. The Martian samples differ in some respects that reflect differences in the compositions of the Martian and terrestrial interiors, but in general are a lot like Earth basalts. Cosmochemistst have used the compositions of Martian meteorites to discriminate bulk properties of Mars and Earth, but McSween and co-workers' synthesis shows that the meteorites differ from most of the Martian crust (the meteorites have lower aluminium, for example), calling into question how diagnostic the meteorites are for understanding the Martian interior.

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Data from the Mars Reconnaissance Orbiter (MRO) suggest the discovery of ancient springs in the Vernal Crater, sites where life forms may have evolved on Mars, according to a report in Astrobiology, a peer-reviewed journal published by Mary Ann Liebert, Inc.
Hot springs have great astrobiological significance, as the closest relatives of many of the most ancient organisms on Earth can thrive in and around hydrothermal springs. If life forms have ever been present on Mars, hot spring deposits would be ideal locations to search for physical or chemical evidence of these organisms and could be target areas for future exploratory missions.
In the research paper entitled, "A Case for Ancient Springs in Arabia Terra, Mars," Carlton C. Allen and Dorothy Z. Oehler, from the Astromaterials Research and Exploration Science Directorate at the NASA Johnson Space Center, Houston, Texas, propose that new image data from the High Resolution Imaging Science Experiment (HiRISE) on MRO depict structures in Vernal Crater that appear to have arisen as part of a major area of ancient spring activity.

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