A tiny lander that crashed on Mars last month flew into the red planet at 540km/h (335mph) instead of gently gliding to a stop, after a computer misjudged its altitude, the European Space Agency has said.
Schiaparelli was on a test-run for a future rover meant to seek out evidence of life, past or present, but it fell silent seconds before its scheduled touchdown on 19 October.
After trawling through vast amounts of data, the ESA said on Wednesday that while much of the mission went according to plan, a computer that measured the rotation of the lander hit a maximum reading, knocking other calculations off track.
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That led the navigation system to think the lander was much lower than it was, causing its parachute and braking thrusters to be deployed prematurely.
“The erroneous information generated an estimated altitude that was negative – that is, below ground level,” the ESA said in a statement.
“This in turn successively triggered a premature release of the parachute and the backshell [heat shield], a brief firing of the braking thrusters and finally activation of the on-ground systems as if Schiaparelli had already landed. In reality, the vehicle was still at an altitude of around 3.7km (2.3 miles).”
The €230m ($251m) Schiaparelli had spent seven months travelling 496m kilometres (308m miles) onboard the so-called Trace Gas Orbiter to within a million kilometres of Mars when it set off on its own mission to reach the surface.
After a scorching, supersonic dash through Mars’s thin atmosphere, it was supposed to glide gently towards the planet’s surface.
For a safe landing, Schiaparelli had to slow from 21,000km/h (13,000mph) to zero, and survive temperatures of more than 1,500C (2,730F) generated by atmospheric drag.
It was equipped with a discardable, heat-protective shell, a parachute and nine thrusters to decelerate, and a crushable structure in its belly to cushion the final impact.
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Giant crater seen in ESA images of Schiaparelli’s crash landing on Mars
A previous attempt to reach the surface of Mars, in 2003, also ended in disappointment when the British-built Beagle 2 robot lab disappeared without trace after separating from its mothership, Mars Express. More than a decade later, it was found that the lander had in fact touched down on the surface, but it wasn’t fully operational.
Since the 1960s, more than half of US, Russian and European attempts to operate craft on the Martian surface have failed.
Schiaparelli and the Trace Gas Orbiter comprised phase one of a project dubbed ExoMars through which Europe and Russia are seeking to join the US in operating a successful rover on the planet.
The next part of the mission is the start of the Trace Gas Orbiter’s mission in 2018, sniffing Mars’s atmosphere for gases potentially excreted by living organisms.
The rover will follow, due for launch in 2020, equipped with a drill to search for remains of past life, or evidence of current activity, up to two metres below the surface.
While life is unlikely to exist on the barren, radiation-blasted surface, scientists say traces of methane in the atmosphere may indicate something is stirring underground – possibly single-celled microbes.
European space officials have insisted that any problems encountered by Schiaparelli would inform the design of the future rover.
“In some ways, we’re lucky that this weakness in the navigation system was discovered on the test landing, before the second mission,” ESA’s Schiaparelli manager, Thierry Blancquaert, said.
“This is still a very preliminary conclusion,” David Parker, ESA’s director of human spaceflight and robotic exploration, said of Wednesday’s findings. “The full picture will be provided in early 2017 by the future report of an external independent inquiry board.”
• This article was amended on 25 November 2016. An earlier version said Beagle 2 had failed to land on Mars. This has been corrected.
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