The European Space Agency has its work cut out for it. Although, the agency has narrowed down candidate landing sites for the Comet 67P/Churyumov-Gerasimenko to just five, choosing the one with the best potential might be tricky.
In November, the Rosetta spacecraft, which is currently in orbit around the comet, will send its Philae Lander to the comet's surface. This historical event is the first of its kind, so the ESA is being careful to make sure that the final chosen landing site provides optimal chances of success.
"This is the first time landing sites on a comet have been considered," says Stephan Ulamec, the mission's lander manager at the German Aerospace Center (DLR). "Based on the particular shape and the global topography of Comet 67P/Churyumov-Gerasimenko, it is probably no surprise that many locations had to be ruled out."
Scientists studied data from Rosetta, including images and measurements of the comet, before choosing 10 sites. After more research, they then narrowed that down to just five.
Each site receives six hours of daylight for every rotation around the comet. This is important because Philae uses solar power after its original battery dies after 64 hours. However, too much sunlight could overheat the lander's probe.
Each site also has relatively flat terrain, making landing easier. The comet is mostly rocky, with large boulders and jagged edges. This makes landing a vehicle on its surface a delicate operation, but finding sites with flatter areas could increase the odds of a smooth landing.
Finally, each site has a high potential for scientific discoveries. All five sites have features that highly interest scientists.
Rosetta's team must also make sure that the Lander can send and receive data from Rosetta, so location is key even for that.
The ESA chooses a final landing site on Nov. 11, after a careful analysis of all five candidate sites. Rosetta will study the sites more closely, and scientists will use that data to rank each site, choosing both a primary landing location and a back-up.
"The process of selecting a landing site is extremely complex and dynamic; as we get closer to the comet, we will see more and more details, which will influence the final decision on where and when we can land," says Fred Jansen, ESA Rosetta mission manager.
The ESA launched Rosetta in 2004 and spent 10 years chasing its comet over 4 billion miles. The spacecraft made history on Aug. 6 when it became the first spacecraft to ever orbit a comet.
