Europe's robot lab Philae may not have enough power to send to Earth the results of today's drill into the surface of its host comet, mission scientists have said.
"We are not sure there is enough energy so that we can transmit" the data, lander manager Stephan Ulamec said at a press conference webcast from European Space Agency (ESA) ground control in Germany.
Scientists are to decide whether to try a risky drilling procedure to enable an exploration probe to examine samples from the surface of a comet before its batteries run out.
The probe on Wednesday floated away from its planned landing site after harpoons designed to hold it down on the comet failed to deploy.
It is now resting precariously on two out of three legs in the shadow of a cliff on the comet.
The lack of light means the probe, dubbed Philae, would not draw sufficient energy to operate on its solar panels as hoped once its batteries run out.
The ESA team are also uncertain of its exact position, making it difficult to "hop" the probe into a better position using its landing gear.
The probe was supposed to drill into the surface of the celestial body after landing, but its unstable position and the comet's weak gravitational pull means there is a risk it could bounce off if the drill is deployed.
Despite the landing setbacks, the mission has achieved many breakthroughs, including the first time a spacecraft has followed a comet rather than just whizzing past and the first time a probe has landed on a comet.
Comets are of interest to scientists because they are remnants from the formation of our solar system, over 4.6 billion years ago.
These masses of ice and rock have preserved ancient organic molecules like a time capsule and may provide insight into how planets and life evolved.
Even if Philae is unable to drill into the surface to analyse samples, the Rosetta spacecraft will follow the comet until at least the end of 2015, even as it passes closest to the sun on its orbit.