Rosetta's Lander is Now Asleep, Waiting for a Brighter Sun

By Sarah Zhang on at

Goodnight, Philae, though not, we hope, goodbye. Before the Rosetta mission's lander ran out of battery life due to a borked landing, scientists scrambled to gather as much comet data as possible. If we're lucky, there's still a small chance of resurrecting Philae.

In case you haven't been following the complete drama of a little machine on a ball of ice and rock 300 million miles away, a couple pieces of Philae's landing gear didn't work. It touched down but then bounced twice, eventually ending up in the dark shadow of a cliff. Philae's solar panels weren't getting enough sun, and when the initial charge on its battery ran out, it went dark, long before its planned March 2015 end date.

But before it died, Philae got to work, more urgently than ever. At top of its priorities was COSAC, or the COmetary SAmpling and Composition experiment, to analyse samples taken 25 centimetres below the surface of the comet. COSAC was looking for organic molecules, especially amino acids that are one of the building blocks of life. Amino acids have chirality, which means they can be left or right-handed, mirror images of each other. The amino acids on Earth are almost all left-handed, and if we find the same on the comet, it would lend credence to the theory that early life on Earth was seeded by comets crashing into our planet. COSAC is especially key because amino acids don't vaporise, so there's no way to study them except on the comet itself. Philae seems to have sent back COSAC data.

Another instrument, Ptolemy, is also gathering data on hydrogen isotopes to determine how much of Earth's water may have originated with comets. Still other instruments have also been gathering data on the thermal and mechanical properties of the comet's surface. The spacecraft Rosetta itself will continue orbiting the comet and return data from its own instruments through August 2015.

A last-minute manoeuvre to rotate a larger solar panel into the sunlight boosts the small possibility that Philae could get enough energy to reawaken. And as the comet itself gets closer to the sun, that possibility could grow.

The ESA has been putting an optimistic face on the comet mission despite Philae's early hibernation, calling it "hugely successful." Philae returned plenty of unprecedented data, even though it had only hours rather than months to collect it.

And for the rest of us watching at home, we weren't watching because we were wondering about the isotopes of a random comet. Ten years ago, humankind sent a spacecraft on a 4 billion mile journey to catch a comet flying 40,000 miles per hour. Then we landed on it, using equipment that had laid dormant for a decade in the vacuum of space. We made—not perfectly, but we made it. [ESA]

Top image: Artistic impression of Philae's descent on a comet. ESA.