The Rosetta spacecraft launched in March 2004, on a 10 year journey to Comet 67P/Churyumov-Gerasimenko. After traveling 6.4 billion km, and an inflight snooze from June 2011 to January 2014, it arrived at the comet in August 2014, and became the first spacecraft to orbit a comet.
In November 2014 the Philae probe landed on the comet – another first for the mission, the first spacecraft to land on a comet. It wasn’t all plain sailing for Philae, unfortunately it didn’t anchor to the surface of the comet as intended, and bounced several times, finally settling in a dark region where it was not getting enough sunlight to power the solar cells. It collected data over the first couple of days, but after just 3 days Philae shut down. Philae did wake again for brief periods as the comet traveled closer to the sun, and just a couple of weeks ago Rosetta finally spotted where it had landed.
Comet 67P passed closest to the sun in August 2015, and since then has been moving away from the sun again. As it continues to move even further from the sun, Rosetta would not receive enough energy from the sun to power the spacecraft. So after over 12 years in space and 786 days orbiting the comet, the mission team decided Rosetta’s final task was to land on the surface of the comet, sending back data and pictures right up till the moment it landed.
So yesterday we waited with baited breath for Rosetta’s signal to disappear forever as it touched down on the comet – it was programmed to turn off all transmitters when it impacted the comet. But the signal, or rather lack of it, took 40 minutes to travel the 718 million km back to Earth. While we were waiting, we saw the closest ever images of the surface of a comet, and got data about the gases and dust coming off the comet from closer than any spacecraft had ever dared venture before.
What have we learnt from the Rosetta mission?
Short answer – lots!
Rosetta photographed this duck-shaped comet from every imaginable angle, sending back thousands of photos, including extreme close-ups yesterday.
It studied the comet as it traveled towards the sun and away again, observing activity on the comet and how it changed, as the distance from the sun changed.
Comets formed from dust and gases left over from when the planets formed very early in the Solar System’s history. The contain some of the oldest, and best preserved material from the birth of our Solar System.
Rosetta analysed dust grains coming off the comet, and gases in its atmosphere. One of the most interesting results is that the water on the comet has a different “flavour” (or isotopic composition) from that on Earth. So it seems that comets like 67P may not have delivered as much water to Earth as previously though
Rosetta also detected chemicals such as glycine and phosphorus which were crucial to the origin of life on Earth. It is possible that these chemicals were delivered to the young Earth by comets.
That’s just a taster of what Rosetta achieved. Scientists will be busy for many years, if not decades, trying to fully understand all the data Rosetta sent back.
So all that remains for me to say is thanks Rosetta, you’ve been fantastic and we’ll miss you! And thank you also to all the scientists and engineers who made this mission possible.