Mars collapse. In 2012, it was proposed that Valles Marineris is not just a graben, but a plate boundary where of transverse motion has occurred, making Mars a planet with possibly a two-tectonic plate arrangement. Images from the Thermal Emission Imaging System (THEMIS) aboard NASA's Mars Odyssey orbiter have revealed seven possible cave entrances on the flanks of the volcano Arsia Mons. The caves, named after loved ones of their discoverers, are collectively known as the "seven sisters". Cave entrances measure from wide and they are estimated to be at least deep. Because light does not reach the floor of most
Mars Exploration Program on Earth, could be used by microscopic life forms living under the Mars' surface. Life on Mars can also be searched for by finding signatures of past and present life or biosignatures. Relative carbon abundance and the location and forms that it can be found in can inform where and how life may have developed. Also, the presence of carbonate minerals, along with the fact that Mars' atmosphere is made up largely of carbon dioxide, would tell scientists that water may have been on the planet long enough to foster the development of life. Another goal of the MEP is