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Nasa finds new evidence of Mars ground-water - Times LIVE
http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1706.html
This view of layered rocks on the floor of McLaughlin Crater shows sedimentary rocks that contain spectroscopic evidence for minerals formed through interaction with water. The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter recorded the image.
Image by: NASA/JPL-Caltech/Univ. of Arizona
http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1706.html
Deposits formed as a result of groundwater upwelling on Mars, such as those in McLaughlin Crater, could preserve critical evidence of a deep biosphere on Mars. We suggest that groundwater upwelling on Mars may have occurred sporadically on local scales, rather than at regional or global scales.
Spoiler
http://en.wikipedia.org/wiki/Species_(film)