It turns out that landing on a comet moving at 84,000 miles per hour is not without its potential pitfalls, and the Philae lander appears to have ended up in something close to an actual pit. In a mission update today, the European Space Agency said that early telemetry data and photos from the lander show that Philae came to a stop at the foot of a large cliff, something that poses problems for harvesting much-needed solar energy for the remainder of its mission. Agency officials said that the current position is only expected to get 1.5 hours of sunlight in every 12 hour rotation on the comet, which is less than half of what was originally planned. The lander's main battery cell is rated for 64 hours before the system relies on solar power.
Harpoons could send it shooting off into space
Power is not the only issue. Philae's harpoons failed to fire in yesterday's landing, leaving it unsecured to the surface. As Nature notes, that could pose problems when it comes time for it to drill, which could further displace it. It might also be too late to attempt to anchor the lander with those harpoons, since the force could send it shooting off back into space, thanks to the comet's extremely low gravity. That nearly happened in Wednesday's landing, after the lander's thrusters had a problem with their cold gas system (meaning they didn't work), and weren't capable of cushioning the probe to keep it from bouncing.
Despite the issues, even getting Philae onto the comet is historic. The mission, which was the first to softly land on a moving comet, promises to advance our understanding of the massive chunks of ice, rock, and frozen gases — especially those that regularly pass through our solar system. The comet Churyumov-Gerasimenko, also known as 67P, was discovered in 1969 by astronomers Klim Ivanovich Churyumov and Svetlana Ivanovna Gerasimenko. It makes its trip around the sun every 6.5 years, while the mission that brought Philae there launched nearly 11 years ago on Europe's Rosetta spacecraft.