On the Cover: Valles Marineris, the Red Planet's "Grand Canyon, " stretches one-fifth of the way around Mars. Within its walls lie records of the planet's geologic past. This computer-constructed mosaic of <i>Viking</i> images shows a portion of Candor Chasma, a small section of the larger canyon complex. In the region shown, the canyon is about 9 kilometers deep and 100 kilometers wide. Its floor is covered with landslide debris and layered deposits, perhaps the remains of an ancient lake.
9 A Soviet View of a Lunar Base: Vladislav V. Shevchenko discusses how humans can colonize the Moon, and what science we should do on the surface.
13 Oceans on Venus—The Great Debate: Charlene Anderson introduces a pair of articles looking at the evidence for and against the presence of past water on Venus:
- 13 The Water That Got Away: James Kasting thinks early Venus may have not been all that different from early Earth.
- 16 Born Wet or Bone Dry? David Grinspoon on the other hand thinks the evidence for oceans on Venus is circumstantial.
3 Members' Dialogue The Moon vs. Mars.
20 News & Reviews Cometary reconnaissance.
21 World Watch Space shuttle Discovery, Soviet Mars missions, and the NASA budget.
23 Society Notes "Invent an Alien" contest, Mars Mania, and the International Space University.
24 Q&A Why does Phobos have such an unique orbit?