The 222nd meeting of the American Astronomical Society was in Indianapolis earlier this month, and one of the plenary talks was an update on the Curiosity mission to Mars. The speaker, Dawn Summer, a geologist at UC Davis, acknowledged up front that she was talking to a room full of astronomers with little or no background in geology. Though planetary science is often grouped with astronomy in the space sciences, the detailed explorations of the rocky planets in our Solar System require an extensive background in geology. Once upon a time I was a TA for Introduction to Geology, but I don’t remember much now, and greatly appreciated the overview for non-geologists!

First, we went over the basics. The Mars Science Lander (MSL), also known as Curiosity, is a roving robotic field geologist the size of a small car. It contains several cameras, an infrared laser to drill through rocks, and a suite of instruments to determine the chemical and mineralogical compositions of rocks. It landed at Gale Crater, thought to harbor evidence of water on Mars. We know at this point that liquid water did exist on the surface of Mars, but we’d like to know more about how much was there and for how long it stayed.

In the less than a year since landing, MSL has provided valuable insight into its surroundings, though it has only moved 500 meters from its landing site. The scientists controlling the rover have stopped to investigate as many interesting targets as they could, hence the lack of range. Recently, outcrops of rock have shown pebble sizes characteristic of stream flows up to a meter deep and carried over several kilometers. Dr. Summer points out that it looks a lot like the now-empty stream beds seem in a Atacama Desert of Chile on Earth. The image at left shows one such outcrop named Hottah.

In addition to the readily visible evidence of stream beds, MSL has also probed into the fractures in rocks that contain water-forming minerals, not unlike that which can form in your bathtub. These calcium and sulfate rich veins are seen by Curiosity’s ChemCam and are very much like similar geological structures seen on Earth. The results of x-ray spectroscopy from another instrument show various clays in existence in these rocks, yet another sign of water.

Although no organic molecules have been seen by breaking down and analyzing the rocks around MSL, the main mission goals have already been met, that being to characterize the an environment that could be conducive to life on Mars. Evidence shows that water flowed through Gale Crater, specifically low-salinity, moderate pH water that people and microbes may find particularly useful for survival. What is left is a dry, dusty desert under an atmosphere far too thin to support human life, but the long rich history of Mars may yet surprise us.

MSL still has 8 kilometers to go until it reached the central peak of the Gale Crater, Mount Sharp. Undoubtedly, the mission team will stop along the way to investigate whatever interesting rocks are found along the way. The panoramas provided by Curiosity show that it would take a good 50 years or more to investigate everything interesting within the rover’s field of view. Sadly, we don’t have 50 years to explore Gale Crater. But the target of Mount Sharp will prove interesting as it is a mountain of sedimentary layers, and thus will provide a look at the geology of Gale Crater over several periods of Martian geologic history. I’d suggest we all stay tuned for the fabulous science to come.