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.
