The comet probe Philae is "asleep" after its batteries ran out and scientists were unable to recharge as it lay in the shadow of a crater wall.
The systems on board the device, which made scientific history this week, have shut down, the European Space Agency (ESA) said.
In a post on its blog, ESA said: "Philae has fallen into 'idle mode' - a possibly long silence. In this mode, all instruments and most systems on board are shut down."
Contact was lost at 12.30am on Saturday morning and the next opportunity for communication is expected to be 10am.
However, the mission, which is the first of its kind, has still been successful.
Stephan Ulamec, lander manager, said: "Prior to falling silent, the lander was able to transmit all science data gathered during the First Science Sequence.
"This machine performed magnificently under tough conditions, and we can be fully proud of the incredible scientific success Philae has delivered."
It took 10 years for Philae and its Rosetta mothership to reach comet 67P/Churyumov-Gerasimenko after an epic journey across four billion miles of space.
Thsee incredible images show the moment the probe dropped from its satellite and first landed on Comet 67P five days ago.
Scientists racing against time to keep the Philae comet lander operating are debating whether to try 'hopping' the probe to a new location.
After the first man-made craft landed on a moving comet we look at the pictures sent back from the daring descent to the historic landing.