The failed British mission to Mars Beagle 2 came "excruciatingly close" to succeeding, scientists say.
New analysis of pictures of the Beagle 2 spacecraft shows that it did not crash-land on the Martian surface but did land and open at least three of its four solar panels successfully.
The Beagle 2 lander was part of a the European Space Agency's Mars Express mission.
It was presumed lost in 2003 for more than a decade after it failed to make contact on landing.
However, satellite images from the Mars Reconnaissance Orbiter (MRO), revealed traces of the missing lander in 2014.
In the latest study, researchers from De Montfort and Leicester Universities used 3D modelling to find best fit with satellite images.
They found a match by simulating the sunlight angles and configurations.
Comparing the two sets of images, they believe almost all of its solar panels were deployed.
It remains unclear why the lander lost contact, but solar panels failing to deploy properly could have blocked signals getting through.
The analysis also suggests that the probe may even have worked for several months, but was unable to send its data back to Earth.
Nick Higgett of De Montfort University said: "We are delighted to say that we have gone way beyond the original plan to reach this exciting conclusion that Beagle 2 did not crash, but landed and probably deployed most of its panels.
"Hopefully these results help to solve a long held mystery and will benefit any future missions to Mars."
The work shows frustratingly that Beagle 2 came so close to working as intended on Mars.