Highlights from the 43rd Lunar and Planetary Science Conference, The Woodlands, Texas, March 19-23

Saturn moon shows some action
Dione, a lesser-known Saturnian moon, has been — and might still be — geologically active. Several lines of evidence from the Cassini spacecraft suggest that the small, frozen moon isn’t just a staid icy rock, said Bonnie Buratti of the Jet Propulsion Laboratory on March 19. For one thing, charged particles emanate from the moon’s surface. Other areas are riven with what Buratti calls “paleo-tiger stripes” — features reminiscent of the steamy fractures on another moon of Saturn, Enceladus, that blast water into space. There’s a feature that looks suspiciously like a cryovolcano, or something that spews ice and other cold materials instead of erupting lava; areas nearby are smooth and relatively crater-free, suggesting that they might have been covered by a frigid eruption. And there’s evidence for a tenuous oxygen atmosphere. Such observations suggest “recent and/or ongoing activity on Dione,” Buratti said. —Nadia Drake

After Titan’s rain, puzzling bright spots
Titan, the behemoth Saturnian moon that has its own weather systems, has tossed another curveball to scientists. Though seasonal rains wet and darken Titan’s surface, some areas become brighter after a storm, reported Jason Barnes of the University of Idaho on March 19. He and his colleagues studied Cassini images of Titan after a September 2010 cloudburst. Following an initial dark phase that lasted for a few weeks, two areas, called Hetpet Regio and Yalaing Terra, became whiter. The light terrain persisted for about a year before fading back to normal. “At first I thought we might be seeing snow,” Barnes said. But snow would first create brighter spots, then melt and darken the surface. Instead, Barnes thinks that evaporating liquids might cool Titan’s surface, causing frost to form. —Nadia Drake

Studying Mars in Greenland
Minerals may be to blame for the surprising amount of methane in Mars’ atmosphere. Scientists from Indiana University in Bloomington are tackling the methane’s source by studying a Martian analog on Earth: fractured, rocky terrain in Kangerlussuaq, Greenland, where the rocks resemble those found near methane-rich spots on Mars. Kevin Webster, a graduate student on the team, reported March 20 on elevated levels of atmospheric methane measured at a site in Greenland. Webster and his team aren’t sure what’s producing the methane, but they’re going back to Greenland this summer to try and find out. Some scientists think that microbes on Mars might be generating the gas, but it’s also possible that non-biological processes — such as those occurring in the types of rocks near Webster’s site — might be the culprit. —Nadia Drake