A pioneering robotic spacecraft has shut down after radioing results of its first and probably last batch of scientific experiments from the surface of a comet, scientists have said.
Batteries aboard the European Space Agency's Philae comet lander were virtually drained on Saturday, shutting down the washing machine-sized probe after an adventurous and largely unscripted 57-hour mission.
Carried aboard the orbiting Rosetta mothership, Philae floated to the surface of comet 67P/Churyumov-Gerasimenko on Thursday, but failed to deploy anchoring harpoons.
Upon contacting the comet's unexpectedly hard surface, it bounced back up into space twice, then came to rest at a still-unknown location about 1km from its original target.
Photos and other data relayed by Philae show it finally landed against a cliff or crater wall, where there was little sunlight to recharge its batteries.
Racing against the clock, scientists activated a series of automated experiments, the first to be conducted from the surface of a comet.
Before dying, Philae defied the odds and radioed its science results back to Earth for analysis.
Its last task was to reposition itself so that as the comet soars towards the sun, Philae's batteries may recharge enough for a follow-on mission.
"Perhaps when we are nearer to the sun we might have enough solar illumination to wake up the lander and re-establish communication," spacecraft operations manager Stephan Ulamec said in a statement.
Scientists are particularly interested in learning about the chemical composition of any organic molecules in samples drilled out from the comet's body.
Comets are believed to be pristine remnants from the formation of our solar system some 4.6 billion years ago.
They contain rock and ice that have preserved ancient organic molecules like a time capsule and may provide insight into how the planets and life evolved.
Philae's drill descended more than 25cm on Friday, penetrating the comet's surface.
"My rotation was successful [35 degrees]. Looks like a whole new comet from this angle," read a message posted on the lander's official Twitter account on Saturday.
Earlier, the scientists tweeted: "First comet drilling is a fact!"
In August, Rosetta became the first spacecraft to put itself into orbit around a comet. It will accompany the comet as it travels towards the sun for at least another 13 months.
Rosetta will use its 11 instruments to analyse the comet over the coming months.
Scientists hope the $1.6bn project, that was launched a decade ago, will help them answer questions about the origins of the universe and life on Earth.