Life on mars? Mars Rover Opportunity finds some of the necessary conditions once existed

Christian Schröder’s research at Tübingen’s Center for Applied Geoscience focuses on the biochemistry of iron minerals. Since the start of the NASA Mars Exploration Rover in 2003, he has been a member of the scientific team responsible for (among other things) the deployment of the Rover’s alpha-particle X-ray spectrometer (APXS), which was developed at the Max Planck Institute for Chemistry in Mainz and is being further developed under the direction of Ralf Gellert at the University of Guelph in Canada. The APXS analyses elements – making it possible to identify the gypsum vein and the nature of the surrounding rock.

Opportunity has been trundling along the Martian soil for eight years now, and has covered more than 33 km. One of its goals has been the crater Endeavour, which is 22 km across and makes geological layers accessible which are older than the sulfur-rich sandstone surrounding Opportuni-ty’s landing site. Along the way, Schröder helped to examine loose rocks on the surface. Some of them turned out to be meteorites, while others were flung there out of impact craters – although not out of “Endeavour,” according to the APXS analyses.

Gypsum, with the chemical formula CaSO4∙2H2O, only forms in water below 60°C. At a higher tem-perature, other minerals, such as anhydrite, CaSO4, would also be present. That means that condi-tions conducive to life once existed on the edge of the crater. Water circulated through cracks in the rock after the crater was made. Had it been high in sulfur, it would probably have led to the formation of the sulfur-rich sandstone found around the landing site.

The crater is of a similar size and makeup to the edges of the Nördlinger Ries crater in southern Germany, a famous example of a crater made by the impact of a large meteor nearly 15 million years ago. Suevite, one of the impactite category of rocks, is composed of ground and broken rock, silicates made molten by the impact as well as minerals only created at high pressures and temper-atures. Suevite was first identified at the Nördlinger Ries and the name comes from the Latin word for Swabia, the region where it is located in southern Germany. The Mars crater “Endeavour” was formed more than 3.7 billion years ago.