NASA's Planetary Protection Office chose a team of Purdue University researchers to evaluate if a sample from the moon Phobos could contain enough material from Mars to include viable Martian organisms. The Purdue team stands with an image of possible particle trajectories from an asteroid impact. Standing from left are professors Kathleen Howell, Jay Melosh, and graduate students Loic Chappaz and Mar Vaquero. Credit: Purdue University photo/Mark Simons