On the Cover: Deer find repose in a bucolic alpine meadow nestled in Olympic National Park. But such scenes of seeming security and timelessness are illusionary—as the dinosaurs discovered 65 million years ago when a comet or asteroid impact wiped them out. Earth resides in a swarm of smaller bodies, many with the potential to wreak havoc on civilization. We have discovered about 10 percent of the near-Earth objects, but one of the many unknown objects may at any time appear and pass through our neighborhood—as did Comet Hyakutake just last year. Such as-yet-undiscovered comets may pose the greatest danger to life as we know it.
4 Opinion: The Green Space Project: To many of us, an alliance of our forces with those of the environmental movement has seemed a natural thing to create. But not everyone feels that way. Noted science fiction author and Planetary Society member Kim Stanley Robinson explores this dilemma.
6 Deep Space 1: Exploration Technology for the 21st Century: Robert M. Nelson and Marc D. Rayman report on this mission, which will test the effectiveness of NASA's new and unofficial motto "faster, better, cheaper."
9 The Mars Rock: Some of its Chemistry is From Earth: In August 1996 the announcement that scientists from NASA and Stanford University had found possible traces of ancient life on Mars touched off a flurry of experimentation and controversy. Gene McDonald reports on two recent studies that question the original findings.
10 Earthly Contaminants Don't Rule Out Martian Life: Members of the team that found the putative traces of ancient life on Mars—David S. McKay, Everett K. Gibson, and Kathie L. Thomas-Keprta—believe that their argument has grown stronger over the past year and a half. Here they counter the recent studies questioning their evidence and its interpretation.
12 Deep Impact: Filming a Cosmic Catastrophe: We don't usually report on films, but Deep Impact explores some of the topics we cover regularly. When we were given the opportunity to review the script, we decided to share our analysis of the producers' efforts with Planetary Society members. Charlene Anderson reports here.
3 Members' Dialogue Shiva impact; comments on the metric system.
16 The Stuff of Life Christopher Chyba looks at why water is necessary.
18 News & Reviews Near-Earth objects (NEOs).
19 World Watch Lunar and Martian mission updates.
20 Q&A Questions about extraterrestrial intelligence.
22 Society News Mars Microphone, new NEO website, and Pathfinder on the BBC.