Scientists struggle to understand how early Earth stayed warm enough for liquid water. (p. 30)

A gravity survey by twin orbiters reveals how much the lunar surface was pummeled by meteorite impacts early in its history. (p. 5)

Deposits didn’t need flowing water to form, new research suggests. (p. 14)

ANCHORAGE, Alaska — On a bright June evening, residents of Anchorage packed the theater in Cyrano’s Off-Center Playhouse, ready to sample some otherworldly dispatches. The messages were beamed to Earth by NASA’s Kepler spacecraft, which circles the sun spying on planets orbiting distant stars. Planet-hunting members of the mission’s science team, in town for an American Astronomical Society meeting, served as translators for the evening, telling tales of far-off worlds that put a twinkle in the spacecraft’s eye. At the time of the summer get-together, the Kepler team had officially... (p. 26)

Lowered by sky crane onto the surface, NASA rover prepares to look for signs that life could have evolved on the Red Planet.

After a safe landing, NASA’s Curiosity begins transmitting images back to Earth. (p. 5)

New analyses of Cassini images reveal ice on the pockmarked Saturnian satellite Hyperion.

Geologic activity and weather on Saturnian moons, and studies in Greenland to learn about Mars. (p. 9)

The solar system’s spotted bully and its ringed sidekick are holding some tantalizing treasures in their gravitational clutches. Circling Jupiter and Saturn are more than a hundred moons, including some of the most promising hosts for extraterrestrial life in the solar system. But not every one of these moons is an equal opportunity extraterrestrial petri dish. Scientists are now debating which might be best for a life-seeking mission. Their attention is focused on a frozen trio: Titan, Enceladus and Europa. For centuries, these satellites appeared in the sky as mere points of light. Now, ... (p. 22)