Fears grow for European Schiaparelli Mars lander
There are growing fears a European probe that attempted to land on Mars on Wednesday has been lost.
Tracking of the Schiaparelli robot's radio signals was dropped less than a minute before it was expected to touch down on the Red Planet's surface.
Satellites at Mars have attempted to shed light on the probe's status, so far without success.
One American satellite even called out to Schiaparelli to try to get it to respond.
The fear will be that the robot has crashed and been destroyed. The European Space Agency, however, is a long way from formally calling that outcome.
Its engineers will be running through "fault trees" seeking to figure out why communication was lost and what they can do next to retrieve the situation.
This approach could well last several days.
One key insight will come from Schiaparelli's "mothership" - the Trace Gas Orbiter (TGO).
As Schiaparelli was heading down to the surface, the TGO was putting itself in a parking ellipse around Mars. But it was also receiving telemetry from the descending robot.
That telemetry could now hold vital clues as to what happened in the crucial minute before the expected touchdown.
Esa experts and those from the industries that built Schiaparelli will examine the downlinked data overnight. They will hold a press conference at 10:00 local time (09:00 BST; 08:00 GMT) on Thursday.
Paolo Ferri, the head of mission operations here at Esa's control centre in Darmstadt, Germany, told reporters: "People will spend the night looking at this data. I'm pretty confident that this telemetry will tell us what action was interrupted when we lost the communications. I would say we have a very good chance tomorrow morning to either know that the lander is lost or to know what attempts we can make to recover it."
If the mood here surrounding Schiaparelli's fate is sombre, there is at least good cheer in the performance of the TGO in getting into its right orbit above Mars.
This satellite is really the key part of the mission formally called ExoMars 2016 - a joint endeavour with the Russian space agency (Roscosmos). The TGO is going to spend the coming years studying the behaviour of gases such as methane, water vapour and nitrogen dioxide in the Red Planet's atmosphere.
Although present in only small amounts, these components - methane in particular - hold clues about Mars' current state of activity. They may even hint at the existence of life on the planet today.
Landing on Mars is always a daunting prospect.
It is necessarily a high-speed approach that has to be got just right or the spacecraft runs the risk of smashing into the ground.
Schiaparelli had a heatshield, a parachute and rocket thrusters in order to slow its approach to the surface.
If the robot is later confirmed as lost, it will clearly be a major blow to Esa which suffered the disappointment of the Beagle-2 lander's failure at Mars in 2003.
But officials here have underlined the fact that Schiaparelli was always viewed within the agency as a technology demonstrator - a project to give Europe the learning experience and the confidence to go ahead and land a more ambitious six-wheeled rover on Mars in 2021.
"This is typical for a test," said Prof Jan Woerner, Esa's director general. "We did this in order to get data on how to land on Mars with European technology. Therefore, all the data we will get this night will be used to understand how to manage the next landing when we go with the rover."
This future vehicle is expected to use some of the same technology as Schiaparelli, including its doppler radar to sense the distance to the surface on descent, and its guidance, navigation and control algorithms.
What will concern commentators is that the budget for the rover is not yet secure. If Schiaparelli is indeed lost, Esa officials may find themselves having to work harder to explain to member states why the extra investment remains worthwhile.