Hundreds of millions of kilometers from earth, a European spacecraft made history Wednesday by successfully landing on the icy, dusty surface of a speeding comet - an audacious first designed to answer big questions about the universe.
However, by Saturday, the European Space Agency says the batteries of Philae - the comet probe - were depleted, but not before delivering reams of data about its surroundings back to Earth.
The ESA says Philae was lifted Friday by about 4 centimeters and rotated 35 degrees in an effort to pull it out of a shadow so its solar panels could recharge its spent batteries. It was not immediately clear whether the difficult rotation was successful in bringing the panels out of the shade.
Even if the rotation was successful, it may take weeks or months before Philae can send out new signals. Regular checks for signals will continue. The last signals were received Saturday morning.
Philae became the first-ever man-made object to land on a comet when it touched down, seven hours after separating from its Rosetta mothership. ESA officials say the probe bounced on the surface of Comet 67P/Churyumov-Gerasimenko twice because its harpoons, which were designed to anchor Philae to the surface, failed to deploy.
The ESA says the 100-kilogram lander has sent back "unprecedented images" of its surroundings. The agency says descent images show the surface of the comet is covered by dust and debris ranging from millimeter to meter sizes, while panoramic views show layered walls of "harder-looking material."
The ESA's team of scientists is now evaluating the data and is attempting to determine whether experiments were successful, especially a complex operation in which the lander was given commands to drill a 25-centimeter hole into the comet and pull out a sample for analysis.
ESA mission chief Paolo Ferri said Saturday the agency was not sure if the drill had touched the ground during the drilling operation.
Scientists hope the $1.6 billion project will help answer questions about the origins of the universe and life on Earth.
Scientists say drilled samples from the comet would unlock details about how the planets evolved. Comets date back to the formation of the solar system 4.6 billion years ago. Scientists suspect impacting comets delivered water to the young Earth.
Matt Taylor, ESA's Rosetta project scientists, says "the data collected by Philae and Rosetta is set to make this mission a game-changer in cometary science."
The Rosetta became the first ever spacecraft to rendezvous with a comet back in August after a 10-year journey that included a slingshot flight path around Earth and Mars before it could gain enough speed to reach Comet 67P.
Rosetta will escort Comet 67P and Philae for the next year and observe it as it heads towards the sun.
