Comet probe's solar panels caught in cliff's shadow

The first photo image from the surface of a comet shows the tiny lander Philae perched in the shadows of a cliff, complicating operation of solar panels needed to keep instruments working, the European Space Agency said Thursday.

The photos show one of Philae's three legs resting on bleak rocky terrain of the comet known as 67P/Churyumov-Gerasimenkohas.

The images, relayed through the orbiting mother ship Rosetta, offered a stunning look from the surface of the comet that is speeding through the universe at more than 80,000 mph.

"Now that I'm safely on the ground, here is what my new home #67P looks like from where I am," Philae tweeted back to Earth, 300 million miles away, on Thursday.

Mission scientist Jean-Pierre Bibring said the first photo from the surface was particularly exciting because it shows "both what man built, the lander, and what nature built, 6 billion years ago, preserved as it was at that time."

The location near a cliff, however, is not ideal, Bibring said Thursday.

"We are just in the shadow of a cliff," he said. "We are in a shadow permanently, and that is part of the problem."

Philae, which bounded onto the duck-shaped comet on Wednesday after a harrowing seven-hour descent and a decade in space, has enough power for about 64 hours and solar panels to extend that for an expected hour each day.

But the shadowy location means that it's getting only 1½ hours of sunlight a day on its panels, rather than the 6 to 7 hours that mission managers had hoped for. The science plan is now being rewritten to maximize scientific results, given the limited amount of battery power.

"The solar arrays are not really illuminated, so we don't know how long we will operate," said Rosetta mission manager Fred Jansen.

In theory, Philae and its scientific instruments could be reawakened as the comet gets closer to the sun in the coming months, but Stephan Ulamec, Philae project manager, said it's far too early to think about that.

Ground controllers are also going to see whether it's possible to nudge Philae — which came to rest with one leg sticking into space — to make sure the panels can catch the sun and charge its batteries, Bibring told reporters.

The final, rocky resting place was in stark contrast to the initial touchdown spot, which was a flat surface.

"We couldn't have had better luck," said Holger Sierks, head of the scientific team for one of the camera's on Rosetta. "We wished it (had) stayed there, but we know it didn't."

Despite years of careful preparation to keep the probe from bouncing upon impact, it shot back from the surface like off a trampoline, staying up for two hours before landing again a half mile away, "which makes it difficult to know where we are now," Ulamec said.

The lander then took yet another small hop before settling down in rugged terrain beside the cliff.

In its awkward final resting spot, with one leg off the ground, managers are almost certain that a drill intended for scientific probing can't be used for fear of toppling Philae even more.

Gravity on the comet is 1/100,000th that of Earth, meaning the washing machine-sized lander weighs just 1 gram (0.04 ounces) there and could simply glide away like a piece of paper.

The probe should have been anchored immediately if three harpoons aboard the craft had fired as planned and punched deeply into the surface.

Ulamec said he would also be hesitant to try to shoot them again because of the lander's unstable position.

It may not be entirely the fault of the machine that Philae didn't stay put. The lander's bounce shows that the comet's surface isn't just a dust field, as expected, but also includes hard surfaces, "which was a surprise to us," Sierks said

Otherwise, the equipment aboard Philae appears to be working well and is sending back a flood of data during communication "windows" when Rosetta passes overhead.

"We had a perfect pass; the radio link was extremely stable and we could download everything according to the nominal plan," said Rosetta flight director Andrea Accomazzo.

Philae and Rosetta will use 21 instruments to analyze the comet over the coming months. Scientists hope the $1.62 billion project will help them better understand comets and other celestial objects, as well as possibly answer questions about the origins of life on Earth.