Describe the journey of a space probe to gather information about a comet. After a more than 10.5-year voyage, this robotic lander has just set down onto the surface of comet 67P/Churyumov-Gerasimenko. On November 12, the day it landed, Philae and its mother ship—the Rosetta spacecraft—were roughly 500 million kilometers (310 million miles) from Earth. 10 Several spacecraft had spent a few hours observing comets from on high as they flew by these mega-boulders. But until Philae’s landing, no mission had placed research instruments onto a comet. The robotic lander has already been sending back photos and probing the rock underfoot. Philae may even get to observe gases or other matter emerging from underground as the comet heats to scorching temperatures. And it will get beastly hot within a few months as the comet’s orbit swings it in close to the sun. 11 For now, scientists are trying to figure out precisely where Philae set down. Problems with a thruster1 kept the lander from holding fast on its first try. 12 Now, instead of being entirely in open space, as planned, the lander is flanked by what looks like a cliff. “We are not sure how far we are from the cliff, but we are in its shadow permanently,” says Jean-Pierre Bibring. A scientist at the Université Paris Sud in Orsay, France, he spoke at a media briefing on November 13. 13 The lander also is not sitting perfectly on all three legs, he noted. It is almost vertical, with two feet on the ground and one in open space. 14 Sitting in a cliff’s shadow also means the lander’s solar panels will get less sunlight than mission scientists had expected. The early data suggest that the lander is getting just 1.5 hours of sunlight per day. That is far less than the six to seven hours it would have gotten if it had landed exactly on target—which it did. At first. 15 On that first touchdown, Philae hit the bull’s-eye. But the lander didn’t stick its landing. Instead, it bounced twice. In between the first and second touchdown, the lander shot a kilometer up into space. In fact, it caught almost two hours of air time before it hit 67P again. The next bounce sent it 20 meters into the air for a 7 minute leap. Researchers are now trying to identify precisely where the lander now sits. 16 But Philae isn’t the only science center studying the comet. Its mother ship, Rosetta, arrived at 67 P on August 6, 2014. Immediately, that spacecraft began orbiting the comet and snapping pictures. Rosetta plans to stay with the relatively tiny celestial rock until at least December 2015. Scientists are hoping that throughout, Rosetta will be able to send back photos. 1thruster: engine on a spacecraft that controls when and how fast it flies Excerpt from “Comet probe may shed light on Earth’s past” by Ashley Yeager, fromScience News for Students. Copyright © 2015 by Society for Science. Reprinted by permission of Society for Science via Copyright Clearance Center.
