On the Cover: An unexpected fruit of the Space Age is the growing awareness that Earth, too, is a planet. We can use the techniques and theories developed for planetary exploratipn to understand and preserve our own—so far as we know—unique home world. Taken from orbit, this Landsat false color image of the abandoned delta of the Ganges and Brahmaputra Rivers shows a confluence of elements seen nowhere else in our solar system: land, liquid water and life. The dark red regions are mangrove forests; the bright blue areas are mudflats; some dark green areas have been claimed by certain Iifeforms for agriculture. MacDonald Dettwiler Corp., Vancouver, Canada
4 Exploring Other Worlds and Protecting This One: The Connection: Carl Sagan explains why it's so important that we protect our planet.
8 Earth, the Living Planet: How Life Regulates the Atmosphere: James Kastingdiscusses life's extensive effects on our planet's atmosphere.
10 Earth in the Mind of Humankind: Richard Berendzengives an historical account of how humans have viewed their place in the cosmos.
12 Earth as a Target for Planetary Research: William Hartmannreminds us that "planetary science" includes the study of our own planet.
16 Mission to Planet Earth: John Duttondetails upcoming missions designed to study Earth.
20 Seeding Earth: Comets, Oceans and Life: Christopher Chybainvestigates the hypothesis that comets may have seeded life on Earth.
3 Members' Dialogue Pluto, Mars rover missions, and Voyager's view of Earth and our Moon.
25 Society Notes Re-name a mission; search for exoplanets.
26 News & Reviews Phobos reports, meteorite mysteries, and early Earth impacts.
27 World Watch NASA's Human Exploration Initiative, and Europe's Mars Exploration Study Team.
28 Q&A What were the "flicker-flashes" seen by Apollo astronauts en route to the Moon?