12 Nov 2014

Eyes on the prize as Rosetta faces comet touchdown

The hardest thing about landing on a comet is making sure you don’t bounce right off.

An average-sized comet – like the target of the European Space Agency’s Rosetta mission, 67P/Churyumov-Gerasimenko – is too small to have much of a gravitational pull.

It’s why Rosetta’s lander, the 100kg washing machine-sized probe called Philae, has been built like no other spacecraft that’s flown before.

It has three shock-absorbing legs, each equipped with ice screws that will spin as soon as it detects a touchdown, hopefully bolting it to the comet’s surface. In case it doesn’t make a perfect footfall, a harpoon will also be fired into the comet to anchor the probe. As a back-up, a small thruster will push down from the top of Philae to overcome the recoil of the lander touching down.

Even with all those gadgets, this is one of the riskiest science missions ESA has ever undertaken.

Rosetta Spacecraft Rendezvous With Comet

Comet 67P/Churyumov-Gerasimenko, photographed by the Rosetta craft (Getty Images)

When Rosetta arrived at 67P, it was immediately clear it was going to be hard to land on. Its craggy, rotten apple-core shape presented few smooth landing surfaces. Once a flattish bit was selected for a landing site, high-res images have revealed numerous boulders easily large enough to scupper a successful landing.

That’s if the mission is on target at all. The comet is tumbling end-over-end every 12 hours or so. The accuracy of orbital “burns” that will put Rosetta into the right position to deploy its lander will only be known seconds before the decision to release has to be made.

Flight controllers have an option to abort the landing attempt at several crucial moments. They have another opportunity to try again later in the month.

GERMANY-EUROPE-SPACE-ESA-COMET-ROSETTA

European Space Agency control room in Darmstadt, Germany (Getty Images)

If they do succeed, however, the prize of landing on a comet can’t be overestimated. Cameras, sensors and tools on Philae have the ability to study the make-up and evolution of the comet in detail planetary scientists have only dreamed of. It will answer questions about the age of the water ice it is made up of, analyse the rocks the ice contains, and look for complex molecules many scientists believe could have seeded life on our primitive planet billions of years ago.

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