ASU scientist: Why do we keep going to Mars?

Because it's the most likely place to find other forms of life in the solar system, says ASU Mars scientist Philip Christensen, in a new NOVA program on PBS.

The hour-long program, "Ultimate Mars Challenge," tells the story of NASA's latest rover, Curiosity, which landed Aug. 5 in Gale Crater. The show was broadcast Nov. 14 and can be seen online at the PBS website.

During the program Christensen explains how, beginning in the 1960s, science from Mars orbit has given us ever more detailed knowledge of the Red Planet. "The orbital view gives you the big picture," he explains.  And this expanding knowledge has increased our desire to explore this neighbor world.

In practical ways, Christensen adds, orbital data has pointed the way for scientists and engineers to find safe, yet scientifically productive sites for landers and rovers. In particular, one of his instruments told NASA where to send its Opportunity rover in 2004. NASA's theme was "Follow the water," and Christensen's Thermal Emission Spectrometer (TES) on the Mars Global Surveyor orbiter found an Oklahoma-size patch of hematite, a water-associated iron mineral in one part of Mars. "The data was screaming at us, 'Come here!'" he says.

The results from Opportunity and its sibling rover Spirit, plus additional data from orbiters, helped scientists identify the best landing site for Curiosity. Curiosity's mission is to look for habitable environments, Christensen says. "When you have the big picture orbital view, dozens of sites have interesting water-related minerals." Gale was chosen because it contains water-altered rocks and sediments. It also contains a three-mile high mountain of layered sediments.

"Geologists' eyes light up when they see layered rocks," says Christensen. The layers form pages from a planet's history book.

Christensen is a Regents' Professor of Geological Sciences in ASU's School of Earth and Space Exploration, part of the College of Liberal Arts and Sciences. He is director of the Mars Space Flight Facility on the Tempe campus and has designed several instruments carried on NASA Mars spacecraft.

Besides the Thermal Emission Spectrometer (TES) on the Mars Global Surveyor, his instruments include the Miniature Thermal Emission Spectrometer (Mini-TES) carried by both Mars Exploration Rovers and the Thermal Emission Imaging System (THEMIS) on Mars Odyssey, which is currently the longest-operating spacecraft (10+ years) at Mars.

Christensen's latest project is building a mineral-scouting instrument on campus in the new Interdisciplinary Science and Technology Building 4 (ISTB4). The instrument, the OSIRIS-REx Thermal Emission Spectrometer (OTES), will fly on NASA's OSIRIS-REx mission to asteroid 1999 RQ36. This asteroid sample-return mission is due for launch in 2016. OTES, which derives its technological heritage from Christensen's Mars instruments, will help scientists map the asteroid's mineralogy and choose the best location to collect a sample.