For many years it was been deemed quite impossible to land an object on a comet. The fast trajectory speed combined with the small size of comets makes such a landing quite a challenge compared to landing on another planet, moon, or even an asteroid, which are much larger and generally closer in distance. The consideration of landing on a comet, however, has been around for several decades. In 1986, probes were sent to pass by Halley’s Comet to collect data regarding its composition.
On November 12, 2014, humanity proved once again that what was thought impossible is actually possible, as the first ever controlled landing on a comet was a success. The European Space Agency’s Philae lander successfully touched down on the surface of the comet 67P/Churyumov-Gerasimenko after 10 years of travelling attached to the Rosetta spacecraft. The comet was only roughly 3 kilometres in diameter, smaller than any other object landed on in the past. Interestingly, the Philae lander had to be harpooned (there were literally harpoons fired from the probe) to the surface of the comet after landing since the escape velocity was so low that it would have ended up bouncing off back into orbit otherwise.
The Rosetta spacecraft was launched, carrying the Philae probe with it, on March 2, 2004 from a launch site in French Guiana. On August 6, 2014, Rosetta achieved an orbit on the comet, the first comet orbit in history. Between then and the landing of Philae, Rosetta collected information for potential landing sites as the surface of the comet had never been mapped and thus there was no pre-determined landing site for Philae.
Although the mission duration was planned to be between 1 and 6 weeks, communication was lost from Philae after 2 days and 7 hours as the probe ran out of power from its primary batteries. Luckily, the probe is equipped with solar panels, and the European Space Agency (ESA) hopes to be able to re-awaken it by August 2015 when the comet will be in an orbital position closer to the sun. There is also the possibility that this will be the last opportunity to continue the mission, since the Sun may very well end up overheating Philae instead.
Despite the short duration of data collection from Philae, a lot of valuable information was gathered nonetheless. The main goals of the mission were to determine physical characteristics and other properties of 67P/Churyumov-Gerasimenko. The comet was found to oscillate at 40-50 MHz, which scientists have modified to be audible to the human ear for the public to hear.
Perhaps the most interesting discovery by Philae was the discovery of chemical compounds on the surface of the comet containing carbon, the building block of life as we know it. The presence of organic molecules on comets has been speculated by scientists for years as a potential origin of life on Earth. Unfortunately, Philae powered down before a full sample could be detected from the icy surface of the comet.
The Rosetta mission was a largely successful subject in social media. The mission had Facebook and Twitter accounts as well as live streams to give updates on the mission as it was happening, with #CometLanding being a trending hashtag.
While this mission is concluded for the time being, there are still several exciting space missions to be on the lookout for, notably the flight test of NASA’s new Orion spacecraft, and the current Expedition 42 sending new astronauts to the ISS, in addition to many more in 2015.
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