Philae probe: Surface of another world revealed

Philae safely on the surface of Comet 67P/Churyumov-Gerasimenko. Picture: PA
Philae safely on the surface of Comet 67P/Churyumov-Gerasimenko. Picture: PA
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THE Philae space probe is sending back “amazing images” after its historic comet landing but there are concerns over the life of its batteries as solar panels are not getting enough sunlight.

A photograph published yesterday by the European Space Agency (ESA) is the first image ever taken on the surface of a comet.

It shows a rocky terrain, with one of the lander’s three feet in the corner of the frame. It is part of a slew of data that Philae is transmitting back to Earth, indicating that its instruments are working properly, said Jean-Pierre Bibring, the lander’s lead scientist at ESA.

Before deciding whether to try to adjust the lander, scientists will spend the next two days collecting as much data as possible while its primary battery still has energy.

The lander’s solar panels were designed to provide an extra hour of battery life each day after that, but this may not be possible now.

“We see that we get less solar power than we planned for,” said Koen Geurts of the lander team. “This, of course, has an impact on our energy budget and our capabilities to conduct ­science for an extended period of time.”

Launched in 2004, ESA’s Rosetta satellite carried Philae on a ten-year, four billion-mile journey to Comet 67P/Churyumov-Gerasimenko, which reached its climax on Wednesday. After two “bounces”, the first one about 1km back out into space, the lander settled in the shadow of a cliff, 1km from its target site.


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The comet is currently streaking through space at 41,000mph, some 311 million miles from Earth. The landing was beset by a series of problems that began when thrusters meant to push Philae on to the comet failed. Then two harpoons, which should have anchored the lander to the surface, were not deployed.

This caused the lander to bounce off the comet and drift through the void for two hours before touching down again. After a second smaller bounce, scientists believe it came to rest in a shallow crater on the comet’s 4km-wide body, or nucleus.

“We are just in the shadow of a cliff,” Mr Bibring said, adding that photos indicate the cliff could be just a few yards away. “We are in a shadow permanently, and that is part of the problem.”

Mr Bibring and his colleagues stressed that the data they will be able to collect with the primary batteries alone will have made the landing worthwhile.

“A lot of science is getting covered now,” he said, noting that scientists would soon get their hands on a tomogram – or scan – of the comet and data showing whether the matter it is made of is magnetised.

But because the lander is just resting on the comet with nothing but low gravity keeping it down, Philae will have to hold off on one of the most important experiments – drilling into the comet to extract material buried beneath the surface.

Scientists want to analyse this material because it has remained almost unchanged for 4.5 billion years, creating cosmic time capsules.

“Drilling without being anchored and without knowing how you are on the surface is dangerous. We might just tip the lander over,” said Stephan Ulamec, head of the lander operation.

Ground controllers will probably wait until the first big batch of data has been collected before attempting to adjust the lander so that its solar panels can catch the Sun and charge its batteries.

Even if Philae uses up all of its energy, it will remain on the comet in “hibernation” for the coming months. In theory, it could wake up again if the comet passes the Sun in such a way that the solar panels catch more light, said Mr Ulamec.


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