Scientists have re-established communication with the Philae space probe, which has made history by landing on a comet, but have concerns about its battery life.
An image from the mission shows the surface of Comet 67P/Churyumov-Gerasimenko - and one of Philae's three feet. Photo: AFP / ESA
The European Space Agency (ESA) said it was receiving fresh data from the probe but that it had landed in an awkward position, the BBC reported.
The lander bounced twice, initially about 1 kilometre back out into space, before settling in the shadow of a cliff, 1 kilometre from its intended target site.
It may now be problematic to get enough sunlight to charge its battery systems.
The ESA mission, launched in 2004, hopes to learn about the origins of our solar system.
It has already sent back the first images ever taken from the crumbling, fractured terrain of a comet.
Listen to more from Mark Bentley of the Austrian Academy of Sciences
'Bizarre' orientation
This collection of frames shows a 360º view of the surface of the comet - with a sketch of the lander superimposed on top. Photo: AFP / ESA / Rosetta / Philae / CIVA
ESA's Rosetta satellite carried Philae on a 10-year, 6.4 billion kilometre journey to Comet 67P/Churyumov-Gerasimenko. It landed on the comet on Wednesday.
After showing an image that indicated Philae's location - on the far side of a large crater that was considered but rejected as a landing site - the head of the lander team, Dr Stephan Ulamec, said: "We could be somewhere in the rim of this crater, which could explain this bizarre… orientation that you have seen."
Pictures taken by Philae of its surroundings show it pressed up against what appears to be a hard wall of some kind.
Telemetry indicates it is on a slope or perhaps even on its side, with one of its three feet not in contact with the surface.
New 'hop' would be risky - ESA
Philae is receiving about 1.5 hours of illumination during every 12-hour rotation of the comet, the BBC reported.
This will be insufficient to top up its battery system once the primary charge it had on leaving Rosetta runs out.
"We have estimations right now that go between Friday afternoon and Saturday afternoon," ESA operation head Paolo Ferri explained.
"It depends on the activities, of course. The more activities we do with the lander, the more power we will consume, and the less time we will have."
Engineers are examining how they might re-orientate the robot to maximise the light reaching its solar panels.
It may also be possible to reconfigure Philae's landing gear and "hop" to a new location, but Dr Ulamec said there may not be enough time to do the analysis required for such a risky strategy.
The robot probe, the size of a washing machine, was dropped from the Rosetta satellite on Wednesday and spent seven hours travelling down to the icy body.
A photo by the ROLIS (Rosetta Lander Imaging System) instrument shows the surface of the comet during Philae's descent. Photo: AFP / ESA / Rosetta / Philae / ROLIS / DLR
This image marks the first touchdown point of the lander - before it bounced twice, settling in the shadow of a large cliff. Photo: AFP / ESA