In 2004, the European Space Agency began a pioneering mission: to land a spacecraft on the surface of a comet. Now, ten years and 6.5 billion kilometres later, their quest has reached its nail-biting conclusion.
On the 12th November, the Philae lander module detached itself from the main probe, and began its descent towards Comet 67P. Mission control waited anxiously to see whether history would be made – and the news was both good and bad. Philae had successfully touched down in one piece, but it had missed its intended landing site, placing it in the shadow of a high cliff face. This meant its solar panels would not be able to re-charge the batteries as intended – a significant disappointment that would shorten the mission’s duration considerably. But things weren’t over yet, and Philae got to work investigating and analysing its surroundings, gathering valuable data while it still could.
Philae had reached Comet 67P onboard a spacecraft named Rosetta, which completed its epic journey using a series of gravitational slingshots. This is when a spacecraft passes close to a planet or other large astronomical body, and uses the gravitational pull to accelerate further into space. Rosetta completed four such manouevres – three times around Earth and once around Mars – before heading out into deep space.
Upon reaching the comet, Rosetta went into orbit and began mapping the surface. After 3 months, it had identified a potential landing site for Philae, but when Philae’s harpoons failed to fire, the lander ricocheted out into space not once but twice. It eventually set itself down in a completely different location – not ideal, but not yet a disaster either.
Philae used its 60 hours of battery life to carry out various scientific experiments: drilling into the comet’s surface, analysing samples, and conveying everything back to mission control for further examination. The data has already yielded significant discoveries, including the detection of organic molecules in the comet’s thin atmosphere. Such a discovery lends weight to the hypothesis that comets provided Earth with the building blocks for life.
Philae’s final act before entering hibernation mode was to reposition its body slightly, in the hope that, over the coming months, it will be able to capture enough sunlight to recharge its batteries. In the meantime, Rosetta continues to investigate Comet 67P from above, following it closely on its journey around the Sun.
Watch What Are Comets? to find out more about how 67P will change as it travels around the Sun.
