On the Cover: The behavior of frosts on Mars may sound like an arcane subject for study, but when you consider that those frosts are made of carbon dioxide and water, and that water is a key to life, the importance becomes clear. This is a crater near Mars' north polar cap, which, like Earth's maintains a permanent covering of frozen water. This crater also retains a permanent layer of frost, unlike other craters of similar size, shape, and location. Why some craters defrost while others don't is one of the many enigmas of Mars.
14 Life on Mars? The Improbable Becomes Probable: Charlene Anderson covers the possible discovery of martian microfossils with a first look at the evidence.
4 Pluto: New Views From the Hubble Space Telescope: Charlene Anderson shows off some remarkable images of the tiny, distant world.
10 Why Mars? Carl Sagan details the many things Mars can teach us.
12 Another New Planet: The Excitement Builds: Charlene Anderson gives an update on the search for extrasolar planets.
16 Robots Versus Humans: The Next Space Race? Louis Friedman asks who will open up new territory in the solar system: human or robots?
18 Society Sponsors Space Research in the Third World: Duncan Steel describes our partnership with the United Nations and the European Space Agency to bring space science to the third world.
3 Members' Dialogue The continuing debate on life in the universe.
15 Society News Scanners for Saturn; new United Nations status.
19 News & Reviews "Life on Mars!"
20 Q&A How can we tell certain meteorites came from Mars?
22 Basics of Spaceflight Thermal control.