On the Cover: Subtle blue-tray clouds hover over the dusty rose Martian surface near Valles Marineris, a series of interconnected east-west canyons spanning roughly 4,000 kilometers (2,500 miles). This is the first color image from the Mars Orbiter Camera aboard <i>Mars Global Surveyor</i>, taken last October 3 about 11 minutes after the spacecraft passed close to the planet for the thirteenth time. It was during these initial passes within the Martian atmosphere that <i>Mars Global Surveyor</i> team members noticed slight movement in an unlatched solar panel, causing mission officials to change the pace of aerobraking, and delaying the mapping portion of the mission one year.
4 The Sun Sets on Mars Pathfinder: Jennifer Vaughn celebrates the new trail to the planets blazed by this true pathfinder.
6 The Shiva Hypothesis: Impacts, Mass Extinctions, and the Galaxy: Biologist Michael Rampino combines discoveries from astronomy, planetary science, paleontology, and geology to piece together a possible story of what has driven changes in life on Earth.
12 Ice, Water, and Fire: The Galileo Europa Mission: Leslie Lowes talks about Galileo's next mission, zeroing in on Europa's ice, Jupiter's water, and Io's fire.
3 Members' Dialogue Going metric, getting into schools, and humans in space.
16 Basics of Spaceflight Where are they now?
18 News & Reviews Hot rocks; Mars mania.
19 World Watch Multiple mission updates.
20 Q&A What forms a comet's tail?
22 Society News NASA takes on the Mars balloon.