The Mars Science Laboratory (MSL), one of the most ambitious planetary missions ever launched, began its journey to Mars in November, 2011, and landed in Gale Crater on the night of 5 August, 2012. Gale Crater is occupied by Mt. Sharp at the center, three times higher than the Grand Canyon is deep. The crater contains a thick section of layered sedimentary rocks holding a story billions of years old. MSL is searching for evidence of environments that may have been conducive to past life, and it carries ten instruments on or inside the Curiosity rover. These include a variety of cameras along with radiation, weather, and chemistry analyzers. The rover also includes a device for analyzing the chemistry of gases in the Mars atmosphere and in soils and rocks (the SAM instrument) and an instrument for detecting the minerals in soils and rocks using a technique known as X-ray diffraction (CheMin). X-ray diffraction is a well-established technique on Earth using much larger laboratory instruments and it can provide more accurate identifications of minerals than any method previously used on the Red Planet.
The MSL experience involved working on Mars time with a 24 hour, 39 minutes solar day (so-called sol). Thus, if you went to work at 0800 today, you would go to work at 2000 in about two weeks. Our work with the rover involved sending commands up to the rover (taking about 14 minutes from Earth to Mars) and receiving data from the rover, every day.
The first photos from MSL showed a variety of volcanic rocks along with what appear to be sedimentary rocks that support the existence of flowing water in the past. Contrary to previous results, analyses of the atmosphere have not found compelling evidence of methane gas. Methane can have a variety of origins, including volcanic and biological, and its absence has important implications in the search for life. The CheMin instrument recently analyzed a sample of martian soil from a dune and found that it is very similar to soils on the flanks of Mauna Kea volcano in Hawaii. Unlike some several-billion-year-old conglomerate rocks that Curiosity investigated a few weeks ago, which are consistent with flowing water, the soil that CheMin analyzed is representative of more modern processes on Mars. The identification of minerals in rocks and soils is crucial to the mission's goal of assessing past environmental conditions because each mineral records the conditions under which it formed. The chemical composition of a mineral or rock provides only ambiguous mineralogical information, as in the textbook example of the minerals diamond and graphite, which have the same chemical composition but strikingly different structures and properties. So far, the materials that Curiosity has analyzed are consistent with our initial ideas of the deposits in Gale Crater recording a transition through time from a wet to dry environment. The ancient rocks, such as the conglomerates, suggest flowing water, whereas the minerals in the younger soil are consistent with limited interaction with water.
Curiosity will spend the next two years traveling across the surface of Gale Crater in search of evidence for past water and environments that may have once been habitable.