Touching the heart of a comet

This comment article is written by Dr Elizabeth Pearson, a Bristol-based space journalist for BBC Sky at Night Magazine. Long obsessed with the stars and all things space, she spends her time trying to understand the mysteries of the Universe. Follow her on Twitter @EzzyP

On Wednesday this week, mankind undertook one of its most daring efforts in space yet and succeeded. We landed on a comet.

The landing was the pinnacle of the Rosetta mission, a project run by the European Space Agency (ESA) that has been over 20 years in the making.

This August, after 10 years in space and travelling more than six billion kilometres, Rosetta finally caught its target. Once in orbit, the probe began looking for the perfect spot to carry out the most audacious space mission since the days of Apollo: to set its Philae lander down on the surface.

It was always going to be difficult, but the first glimpse of the comet revealed exactly how monumental the task was going to be. The comet was a contact binary, two lumps of ice stuck together, meaning huge portions of the surface were impossible to land on. And it was spinning.

After weeks of deliberation the team found the best spot and on Wednesday Philae separated from Rosetta, bound for the surface of the comet.

Perhaps the most astounding part of the whole landing was the fact that once Philae had been released, it had no way of steering. The entire landing depended on the trajectory calculated by scientists 500 million km away, back on Earth.

It was an arduous seven-hour wait as Philae made the 10km journey to the comet, but at 1600 GMT the word came in. Touchdown.

But the joy was short lived. Something wasn’t quite right. Ten years in space, subject to a near perfect vacuum, freezing temperatures and the constant bombardment of solar radiation, had taken its toll on the lander. All three mechanisms meant to secure the lander to the surface had failed. It had bounced.

By the time it came to rest, Philae had travelled more than a kilometer away and appeared to have landed slightly off-kilter in the shadow of a cliff.

The lander’s tilt and shady location means that it may not be able to perform all the experiments that researchers had hoped. However, the research teams have already begun getting as much science out of Philae as they can before its batteries run down.

Even if these few days are the only science we can get out of Philae, the Rosetta orbiter will continue to follow the comet as it travels around the Sun for another year. While the lander could only sample a tiny portion of the surface, Rosetta will keep watch over the entire comet.

Rosetta was the first major mission undertaken by ESA, who at its inception were still a newcomer to space. There were many at the time that thought such a huge mission was impossible, even for the likes of Nasa. While we had visited comets before in brief flybys, in order to keep up with a comet the mission would be required to reach huge speeds and with unprecedented accuracy.

The landing would required a probe capable of thinking for itself, as Rosetta is so far away there is a 28-minute delay in communications, similar to the Curiosity lander that touched down on Mars. Only Rosetta was developed a decade earlier and would be approaching a surface no one had seen before.

To achieve their goals ESA brought together experts from more than 15 countries, pushing the technology of the day to the limits to achieve the goal. With its success, Rosetta has shown what can be accomplished when many minds and nations come together, working towards a greater purpose.

With this mission, ESA has cemented itself as a superpower in the field of space exploration. This is a big step not only for the agency itself, but for the fledgling nations, such as India and South Korea, whose own space agencies are just beginning to come into their own, showing that these audacious missions are not just for Russia and the United States.

Inspired by Rosetta, there are already plans to hijack an asteroid and place people on its surface, and the experience we earned from this mission will be invaluable in making that happen.

No matter what becomes of Philae, the landing has been a huge triumph not only for ESA, but for humanity. We now live in a world where mankind has touched the heart of a comet.

Pictures: Image of the surface of the comet from the Philae lander, seen on its final journey to the surface / ESA