At first glance, Mars might seem rather different from our own planet. Mars is dry, with little atmosphere, and no liquid water on its surface. It is half the size of Earth, lacks a planetary magnetic field, and does not appear to have active plate tectonics or volcanic activity. In some ways it is a world frozen in time, affected only by the force of wind and the occasional meteorite impact.That static nature, however, could give scientists clues to conditions that once existed on Earth, but have been lost to the effects of plate tectonics and weathering. Ira talks with planetary geologist Dr. Valerie Payré of the University of Iowa about her research into the geology of Mars, and what it could tell scientists about early Earth.Transcripts for each segment will be available the week after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.