The Cassini spacecraft buzzed past Saturn's moon Iapetus yesterday, coming within 1,000 miles of its surface. The walnut-shaped moon has a band of relatively large mountains running around its equator, and appears two-toned, with one hemisphere bright and the other dark as night. Cassini flew by it in 2004, but it's going to be 100 times closer this time, and scientists hope this final look will help them figure out some of Iapetus's strange features. The results of some of the data gleaned will be presented at a planetary science conference in October.—Gregory Mone

Via NASA

Vapor plumes on Enceladus, Courtesy Ciclops.org

The Cassini spacecraft has found evidence of geysers on Enceladus, a strange, cold moon of Saturn. This discovery brings the total number of places in the known universe with liquid water to two: there and Earth. (Mars had liquid water long ago, and Jupiters moon Europa is only suspected of having a liquid ocean buried under ice.) Carolyn Porco, the always-enthusiastic Cassini imaging team leader, describes the findings thusly in her e-mail announcement:

What we have discovered about the story of Enceladus is thrilling beyond imagination: more heat emerging from the south polar region, per square meter, than from the Earth and, possibly, subterranean organic-rich bodies of liquid water only tens of meters beneath the south polar terrain. If we did nothing else, these findings alone would have made the Cassini mission worthwhile.

Weve written about Cassini twice in recent years: a preview of the mission as it arrived in July 2004 and an update on its incredible findings in April 2005. Perhaps its time for another look. —Michael Moyer

The penetrometer was the first thing to hit. The stick-like probe on the bottom of the Huygens lander punched aside a hard pebble made of water ice on the surface of Saturn’s largest moon, Titan, and sliced down through five inches of soft, muddy material. Scientists watching from Earth were ecstatic—the probe was not expected to survive the landing—but at the same time puzzled: If Titan really was, as they suspected, much like a young Earth, where were the liquid oceans predicted to cover the surface?

Seven years ago, the largest and most expensive interplanetary probe ever built blasted off from Cape Canaveral. It was loaded with 12 advanced scientific instruments, 72 pounds of plutonium to power them, and a capsule destined to be jettisoned toward the only other object in our solar system protected by a nitrogen-based atmosphere. After launch, the spacecraft began its voyage through the void of space and was promptly forgotten by all but a few scientists and space enthusiasts.

Galileo, the interplanetary spacecraft that has changed the way we understand Jupiter and its 61 known moons, will perish on the 21st of this month as it plunges into the Jovian atmosphere. NASA engineers have put Galileo on a collision course with the planet so that the spacecraft, which is running low on propellant, can study the Jovian magnetosphere as a final task. The suicide mission will also ensure the craft won't end up crashing intoand possibly contaminatingthe ocean of Europa, one of Jupiter's moons.