Scientists are facing an anxious wait before they can learn whether Europe's first Mars landing has been successful after revealing the signal from the probe was lost.
The European Space Agency (ESA) from the operations centre in Germany said the fate of the Schiaparelli lander may not be known until tomorrow morning.
"We saw the signal through the atmospheric phase, the descent phase - at a certain point it stopped," said Paolo Ferri, ESA head of missions operations.
"This was unexpected but we couldn't conclude anything from that because this very weak signal picked up on ground was coming from an experimental tool."
Ferri said it was too early for conclusions but "it's clear these are not good signs".
He said there was a lot of data to be worked through, adding: "We should remember this landing was a test. As part of a test you want to know what happened.
"It's fundamental that tonight we look at this telemetry. I'm quite confident that tomorrow morning we will know."
He added analysts would work through the night and the answer may come before a planned press conference.
Ferri said their objective was to have a "very good story" before then or they would look a "bit hopeless".
Schiaparelli separated from its own mothership, the ExoMars Trace Gas Orbiter, on Sunday after a 500 million km (310 million miles) seven-month journey through space.
At 3.42pm UK time, it was due to begin a "six minutes of terror" journey through the Martian atmosphere. During this time the probe was travelling on autopilot and mission controllers on Earth could only sit and wait - hence the "terror".
Although it carries some instruments, Schiaparelli's main job is to test out the Russian-designed landing system for a future ExoMars rover mission due to be launched in 2020.
Initially slowed by the friction on its heat shield, the probe should have deployed its parachute at an altitude of about 11km (6.8 miles).
As it neared the ground, three clusters of retro rockets were supposed to fire, slowing the craft's speed to less than 7km/h (4.3mph) two metres (6.5ft) from the surface.
The rockets were then due to switch off, allowing the probe to drop the rest of the way.
A special crushable structure built into the spacecraft was meant to cushion against the final shock.
During the descent Schiaparelli was programmed to take pictures of the approaching Martian terrain.
The landing site is Meridiani Planum, a flat region that interests scientists because it contains an ancient layer of haematite. On Earth, the iron oxide mineral almost always forms in a watery environment.
Schiaparelli was due to spend about four days gathering weather data before its batteries ran out.