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Rolling Boulders on a Comet

A 100-foot-wide boulder on the surface of Comet 67P/C-G (ESA/Rosetta/MPS)

See that big rock there? (It’s easy because there’s a big yellow arrow pointing to it.) That’s a 100-foot/30-meter wide boulder that was imaged sitting on the surface of Comet 67P/Churyumov-Gerasimenko by ESA’s Rosetta on May 2, 2015. Nine months later Rosetta captured another image of the same area in which that huge stone had clearly moved—find out below just how far!

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Revisit Our First (and Only) Landing on Titan

View from Huygens’ camera as it descended to the surface of Titan on Jan. 14, 2005. ESA/NASA/JPL/University of Arizona

When you think of spacecraft landings on other worlds, you probably first think of Mars, the Moon, Venus, and comet 67P (if you’ve been following along over the past couple of years.) But—in addition to the asteroid Eros and hard impacts on a comet and Mercury—Saturn’s moon Titan was also visited by an alien (i.e., Earthly) spacecraft back in January of 2005. ESA’s Huygens probe, which traveled to Saturn onboard the Cassini orbiter, was deployed to the surface of Titan six months after Cassini arrived in orbit at Saturn. Huygens took 20 days to reach the cloud-covered moon, and during its two-and-a-half hour descent on Jan. 14, 2005 transmitted our first—and last—views from below Titan’s clouds and even from its methane-slush-covered surface. It was the first landing on a moon other than our own and the farthest landing from the Sun, but hopefully not the final time we’ll visit the fascinating surface of this icy moon.

Read more and watch the video of the Huygens probe landing on the Cassini mission site: Huygens: ‘Ground Truth’ from an Alien Moon

Could This Asteroid Hit Earth? Astronomers Go “Back in Time” to Find the Answer

Potentially hazardous asteroid 2016 WJ1 was discovered in Oct. 2016—but also in July 2003. Credit: Canada-France-Hawaii Telescope

Astronomers are always watching the skies for observations of near-Earth asteroids—”space rocks” that have orbits close to Earth’s and, in the case of potentially hazardous asteroids (aka PHAs), those whose orbits could actually cross Earth’s and are larger than 150 meters (500 ft) across. When a new one of these is discovered—no small feat considering that many are very dark, move quickly, and could really be anywhere in the sky—it’s a scramble to determine the object’s orbital parameters and figure out just how close it can get to us and when. Such was the case on Oct. 19, 2016, when the asteroid 2016 WJ1 was identified with the Catalina Sky Survey. This object, estimated to be anywhere from 110 to 340 meters across—easily within the potentially hazardous range—was initially calculated to pose a threat in 2065 with a possible impact risk, albeit a very small one. Eventually though, scientists were able to refine the risk chance with more observations of 2016 WJ1…observations that had actually occurred over 13 years earlier.

Read the full story from ESA here: Asteroid sleuths go back to the future

Light and Dark: the Two Faces of Dione

Global map of Dione’s surface. NASA/JPL-Caltech/SSI/LPI

Saturn’s moon Dione (pronounced DEE-oh-nee) is a heavily-cratered, 700-mile-wide world of ice and rock, its surface slashed by signature “wispy lines” that mark the bright faces of sheer ice cliffs. But Dione has some strange colorations too, evident here in a global map created in 2014 from Cassini images. Its leading half—the side that faces “forward” as it moves around Saturn in its tidally-locked orbit—is pale and bright, while its trailing hemisphere is stained a brownish color, the result of surface interaction with  charged particles in Saturn’s magnetic field.

Read more from ESA here: Space in Images – Global colour mosaic of Dione and see more pictures and news about Dione here.

With One More Comet Landing Rosetta’s “Rock and Roll” Mission is Ended

ESA's Rosetta mission has come to an end with the spacecraft's impact on Sept. 30, 2016. (Illustration by ESA/ATG medialab)

ESA’s Rosetta mission has come to an end with the spacecraft’s impact on Sept. 30, 2016. (Illustration by ESA/ATG medialab)

Rosetta is down. I repeat: Rosetta is down.

This morning, Sept. 30, 2016, just after 10:39 UTC (6:39 a.m. EDT) ESA’s Rosetta spacecraft ended its mission with an impact onto the surface of the comet 67P/Churyumov-Gerasimenko. The descent, begun with a final burn of its thrusters about 14 hours earlier, was slow, stately, and deliberate, but even at a relative walking pace Rosetta was not designed to be a lander like its partner Philae and thus ceased operation upon contact with the comet.

With the comet 446 million miles (719 million km) from Earth at the time, the final signals from Rosetta were received 40 minutes after impact, officially confirming mission end.

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