What happened to the UK's Beagle 2 Mars probe on Christmas Day 2003 is once more unclear.
In December 2008, engineers led by Madhat Abdel-Jawad at the University of Queensland thought they had cracked it when their simulations showed Beagle 2's gyroscopic spin was too fast for it to remain stable - so it would have tumbled and burned up in the Martian atmosphere (New Scientist, 20 December 2008, p 24).
The Beagle 2 team is far from convinced. Arthur Smith of Fluid Gravity Engineering in Emsworth, Hampshire, UK, says the Australian team failed to simulate atmospheric entry in a gravity field, or allow for Beagle 2's offset centre of gravity, meaning the simulations were flawed. With the parameters set correctly, Smith's simulations show that Beagle 2 did not tumble.
Smith and colleagues at the Open University and Aerospace firm EADS Astrium in the UK plan to explain their analysis in a forthcoming research paper.
Abdel-Jawad and his colleagues are looking forward to reading it. "All our assumptions were valid over the time of flight we analysed," he says. "We would be delighted to accept the findings of the Beagle team's new study if it were found to be valid after we review their analysis."
This was first published in August 2009