A burst of sunshine in the spring could be just the wakeup call for Europe's comet lander.
Scientists raised hopes Monday that as the Philae lander nears the sun its solar panel-powered battery will recharge, and the first spacecraft to touch down on a comet will send a second round of scientific data back to Earth.
Since landing with a bounce on the comet Wednesday, Philae has already sent back reams of data that scientists are eagerly examining. But there were fears its mission would be cut short because it came to rest in the shadow of a cliff. Its signal went silent Saturday after its primary battery ran out.
Shortly before its primary battery ran out, the European Space Agency decided to attempt to tilt the lander's biggest solar panel toward the sun — a last-ditch maneuver that scientists believe may have paid off.
"We are very confident at some stage it will wake up again and we can achieve contact," Stephan Ulamec, the lander manager, told The Associated Press.
That should happen next spring, when Philae and the comet it is riding on — called 67P/Churyumov-Gerasimenko — get closer to the sun, warming up a secondary battery on board. A few days of sunshine on the solar panels should be enough to charge the battery sufficiently to conduct science runs, said Ulamec.
Philae's position in the shadows may even prove to be a blessing in disguise. Shielded from the sun's rays, the lander could survive for longer as the comet approaches perihelion — its closest point to the sun — in August.
Before they can say for certain if they'll be able to restore contact with Philae, scientists first need to find out where on the 4-kilometre (2.5-mile)-wide comet the washing machine-sized lander is, he added.
New pictures released Monday offer very good clues about where it has come to rest.
The high-resolution images taken from Philae's mother ship Rosetta show the lander descending to the comet and again after its first and second bounce. These were caused by the lander's failure to deploy its downward thrusters and harpoons.
Surface tougher than thought
Scientists at the German Aerospace Center, DLR, said Monday that an initial review of data the lander sent back 500 million kilometres (311 million miles) to Earth showed the comet's surface is much tougher than previously assumed. There's also evidence of large amounts of ice beneath the lander.
Scientists had speculated the comet's surface could be quite soft, but that has turned out not to be the case. "The strength of the ice found under a layer of dust on the first landing site is surprisingly high," said Klaus Seidensticker of the German Aerospace Center.
Scientists are still waiting to find out whether Philae managed to drill into the comet and extract a sample for analysis.
Material beneath the surface of the comet has remained almost unchanged for 4.5 billion years, so the samples would be a cosmic time capsule that scientists are eager to study.
One of the things they are most excited about is the possibility that the mission might help confirm that comets brought the building blocks of life — including water — to Earth.
Tantalizingly, one of Philae's instruments was able to "sniff" the presence of organic molecules on the comet, the space center said. A full analysis of the molecules is still underway.
The European Space Agency has stressed that even if the lander fails to awaken again, Rosetta will be able to collect about 80 per cent of the data scientists are hoping to glean from the $1.6 billion mission.
Early results from the ongoing Rosetta mission are expected to be released next month at the American Geophysical Union conference in San Francisco.