A robotic space lander has surprised scientists by waking up and sending a signal to Earth, seven months after straying into the shadows of a comet where they feared it might be marooned for ever.

The European Space Agency said yesterday that it had received signals from the lander, named Philae, late on Thursday, when it began “speaking” with its team on the ground for the first time since it went into emergency hibernation following a botched landing on the comet in November.

Scientists believe the space probe is receiving increasing amounts of sunlight as the comet speeds closer to the sun, enabling its solar panels to produce the power needed for it to send data.

“There’s great excitement about it being back,” ESA senior science adviser Mark McCaughrean told Reuters by telephone. “But we have to make sure it’s not the last croak of a dying cowboy.”

Robotic space lander on the comet went into hibernation on November 15

In the shadows, Philae’s solar panels, which were meant to power the probe after its batteries ran out several days after landing, received far less than the expected six to seven hours sunshine per day. It went into hibernation on November 15.

After re-awakening, Philae “spoke” for 85 seconds with its team on the ground via its mother­­ship Rosetta, which is orbiting the comet at a distance of about 6.5 kilometres. Analysis of the detailed data suggests the lander had been awake earlier but unable to make contact, ESA said.

“It’s very fascinating and we’re all very happy to have received this signal,” project manager Stephan Ulamec said.

“The lander seems to be perfectly healthy.”

Philae official Twitter account also came back to life yesterday, tweeting: “Hello Earth! Can you hear me?”

Scientists hope that samples drilled from the roughly three-by-five kilometre comet by Philae will unlock details about how the planets – and possibly even life – evolved. The rock and ice that make up comets preserve ancient organic molecules like a time capsule.

The lander was released from Rosetta in November after a 6.4 billion kilometre journey that took more than 10 years – a mission that cost close to €1.4 billion.

But harpoons to anchor Philae to the surface failed to deploy and it bounced twice before floating to rest two hours later. Scientists scoured the surface of Comet 67P/Churyumov-Gerasimenko for months in the hope that the lander would revive.