A European space lander reached Mars on Wednesday in what scientists hope will mark a major milestone in exploration of the red planet, but whether it touched down on the surface safely was far from certain.
Older European and US spacecraft already in orbit relayed data of the lander's six-minute descent. Then transmission stopped, leaving questions over what state the disc-shaped 577kg Schiaparelli probe was in.
"It is clear that these are not good signs," said Paolo Ferri, the European Space Agency's (ESA) head of mission operations.
However, the primary part of the mission, bringing the lander's mothership into orbit around Mars to search for signs of life, was a success, the agency said.
"To fly to Mars is a very big challenge. To fly and be in safe orbit is a very big challenge," ESA director general Jan Woerner said at ESA's Space Operations Centre in Darmstadt, Germany.
Schiaparelli, which is testing technologies for a rover due to follow in 2020, represents only the second European attempt to land a craft on the red planet. Britain's Beagle 2 was ejected from the Mars Express spacecraft in 2003 but never made contact after failing to deploy its solar panels on landing.
At the time it was dubbed "a heroic failure".
ESA said more information about Schiaparelli should be available on Thursday, when scientists have had a chance to analyse data from the orbiting craft.
"Cross your fingers, we still have hope," Woerner said.
Landing on Mars, currently some 56 million kilometres away from its nearest planetary neighbour Earth, is a notoriously difficult task that has thwarted most efforts by Russia and given US space agency NASA trouble as well.
The planet's hostile environment has not detracted from its allure, with US President Barack Obama recently highlighting his pledge to send people to the surface by the 2030s.
"With this mission we're laying the foundation for going there," astronaut Alexander Gerst, who is set to become the first German commander of the International Space Station in 2018, told Reuters TV.
Elon Musk's SpaceX is developing a massive rocket and capsule to transport large numbers of people and cargo to Mars with the ultimate goal of colonising the planet, and the U.S. entrepreneur has said he would like to launch the first crew as early as 2024.
LIFE ON MARS
The primary goal of ExoMars is to find out whether life has ever existed on Mars. The spacecraft on which the Schiaparelli lander travelled to Mars, Trace Gas Orbiter (TGO), carries an atmospheric probe to study trace gases such as methane around the planet.
Scientists believe that methane, a chemical that on Earth is strongly tied to life, could stem from micro-organisms that either became extinct millions of years ago and left gas frozen below the planet's surface, or that some methane-producing organisms still survive.
"If there is life in our solar system beyond Earth, then Mars is the most interesting planet," ESA's Woerner said.
The second part of the ExoMars mission, delayed to 2020 from 2018, will deliver a European rover to the surface of Mars. It will be the first with the ability to both move across the planet's surface and drill into the ground to collect and analyse samples.
The ExoMars 2016 mission is led by the European Space Agency (ESA), with Russia's Roscosmos supplying the launcher and two of the four scientific instruments on the trace gas orbiter. The prime contractor is Thales Alenia Space, a joint venture between Thales and Finmeccanica.
The cost of the ExoMars mission to ESA, including the second part due in 2020, is expected to be about €1.3 billion ($NZ1.8 billion). Russia's contribution comes on top of that.
