EVENTS For information on JPL tours and the speakers bureau, visit our PUBLIC SERVICES site. The Solar System Ambassador Program sponsors events in communities around the country. Find out how to become a volunteer Solar System Ambassador.		Topic - MARSIS Instrument on the Mars Express Spacecraft Radar Sounding of Mars: MARSIS on Mars Express Presented by Dr. Jeffrey Plaut Co-Principal Investigator, MARSIS Instrument, Mars Express Spacecraft RealPlayer (with caption): "Radar Sounding of Mars" Archived Webcast RealPlayer (w/o caption): "Radar Sounding of Mars" Archived Webcast If you don't have RealPlayer, you can download the free RealPlayer 8 Basic.   Thursday, April 13 The von Kármán Auditorium at JPL 4800 Oak Grove Drive Pasadena, CA For directions, click here. Friday, April 14 The Vosloh Forum at Pasadena City College 1570 East Colorado Blvd. Pasadena, CA For directions, click here. Both lectures begin at 7 p.m. PDT and run for approximately an hour. Admission is free. Seating is limited. For more information, call (818) 354-0112. For the first time in the history of Mars exploration, a radar sounder has been used to probe below the surface of the planet. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), aboard the European Space Agency's Mars Express orbiter, has been bouncing radar signals off of Mars and its ionosphere since June, 2005. MARSIS is being used to map the interior of the thick polar ice caps to depths as great as 3 km (2 miles), and has discovered large hidden craters below the surface. It is also probing the ionosphere, discovering complex structures and mapping the magnetic fields of Mars in exciting new ways. To learn more about the Mars Express Mission, click here.