The Rosetta mission’s hibernating lander could awake within weeks, according to new predictions that it will soon be receiving enough sunlight to recharge its batteries.

The Philae probe shut down just three days after making a spectacular, but bumpy, landing on the duck-shaped comet, 67P/Churyumov-Gerasimenko and has been in a dormant state ever since. Despite making it to within half a mile of its target on the comet’s “head”, after a 250 million mile journey through space, the lander came to rest in the shadow of a cliff meaning that its solar-powered batteries have been unable to recharge since November.

As the comet approaches the sun, the lander will be experiencing more intense sunlight, and the latest analysis suggest it could enter its re-booting routine within weeks.

Stephan Ulamec, the lander manager, said: “What we’ve learnt is that the power will probably be sufficient ... The lander may be able to boot in April or May.”

For it to switch back on, two key conditions need to be met, Ulamec added. First, the interior of the lander needs to be at least -45C before it can be switched back on safely.



“The lander is designed in a way that if the temperature is below -45C, power on board would be used for heating rather than booting the computer,” said Ulamec.

Second, Philae needs to be able to harvest enough energy from its solar panels to reboot and re-establish communication with its mothership Rosetta, which is tracking the comet from around 200km away. It is already receiving more than twice the amount of solar energy than in November, the scientists calculate, based on their best estimates of the position of the lander.

“The situation is improving every day as we’re approaching the sun, but we are very cold - this is the problem,” Ulamec told the European Geosciences Union General Assembly, in Vienna today.

Assuming the interior of the lander warms up enough, the Rosetta team predict that communications could be re-established by May or June and that by July and September Philae is likely to be getting enough energy to recharge its batteries, allowing it to continue operations at “night-time”, when it is not in direct sunlight.

Ultimately, it may be possible to re-operate the lander’s drill and collect more surface samples, which would be baked in a small on-board oven to analyse the gases given off. In November, a drilling attempt was not completely successful, and scientists are not sure if the sample was collected properly. “I would dream of having another sample from the surface,” said Ulamec. “At the start we’ll have to be more modest though.”

Scientists now know that when deployed in November, Philae rebounded twice from the comet’s surface before coming to a final standstill. Although this ultimately left the craft asleep in the shade, it did mean that data was obtained from several points on the surface.

A new analysis of these results, together with measurements made by Rosetta, have shown that, contrary to prior expectations, the comet does not have its own magnetic field.

“The unplanned flight across the surface actually meant we could collect precise magnetic field measurements with Philae at the four points we made contact with, and at a range of heights above the surface,” said Hans-Ulrich Auster, a Rosetta scientists and lead author of the findings published today in the journal Science.

The discovery challenges one of the leading theories on how comets and the precursors of planets first began to form in the infant solar system.

Initially, the sun was surrounded by just a swirling disc of gas and dust and it was thought that magnetic fields, created by charged particles flowing from the sun, may have played an important role in drawing together clumps of material in space, like iron filings being pulled in by a magnet.

The latest measurements found no evidence that magnetic material such as iron is organised within the comet 67P, which it would have been if magnetism had first drawn it together.

Andrew Coates, head of planetary science at UCL’s Mullard Space Science Laboratory, said: “The problem with solar system formation has always been what gets it going in the first place.”

According to Ulamec: “One leading theory has to be deleted from the textbook now.”

The findings suggest that swarms of particles may have simply stuck together when they happened to bump into each other, eventually snowballing into masses big enough to have sufficient gravity to accumulate further material.