The Philae lander that touched down on a comet detected organic molecules containing carbon, similar to what formed the basis of life that developed on Earth, scientists have announced.

A German-built instrument on the lander sampling the thin atmosphere of comet 67P/Churyumov-Gerasimenko detected the molecules, although their exact composition has not been determined and will require further study of the data, project scientists with the European Space Agency say.

Also not yet known is whether they contained the complex compounds necessary to make up proteins, they say.

A key goal of the mission of the Rosetta spacecraft orbiting the comet and the Philae lander it sent down to the surface is to determine if the potential for life on Earth may have been delivered in impacts of comets bearing carbon-based organic compounds.

Philae was able to transmit 60 hours of scientific data from its onboard suite of instrument before its batteries ran out of energy, scientists said.

"We have collected a great deal of valuable data, which could only have been acquired through direct contact with the comet," said Ekkehard Kuhrt, scientific director for the Philae mission at the German space agency DLR.

"Together with the measurements performed by the Rosetta orbiter, we are well on our way to achieving a greater understanding of comets."

Comets, many of them as old as the solar system itself, could be "time capsules" preserving ancient organic compounds or molecules, the scientists said.

Before Philae ran out of power -- its final landing spot was in the shadow of a cliff that prevented as much sunlight from hitting its solar panels as was desired-- it managed to deploy an instrument arm to examine the characteristics of the comet's surface.

A thermal sensing instrument meant to be driven 15 inches into the comet's surface was deployed, but was unable to penetrate the icy surface under a thin layer of dust even at its hammer's highest setting.

"It's a surprise," said Tilman Spohn, who leads the DRL team in charge of the sensor instrument. "We didn't expect such hard ice on the ground."

The ice, frozen to temperatures existing in the outer solar system, was as hard as sandstone, scientists said.

They expressed hope that some of Philae's instruments might be able to resume operations as the comet nears the sun and more intense sunlight might eventually reach the lander's solar panels, recharging its batteries.