Nasa's Curiosity Mars rover has been placed on 'standby' after attempts to complete vital repairs to its computer systems were hampered by a massive solar flare.
The rover has been in 'safe mode' for about a week after a memory problem virtually knocked out its primary computer.
Nasa said that there was no cause for serious concern, and expected the process of switching to a backup 'B' computer to take about 10 days.
But that has been delayed after the sun expelled a "medium strength" flare which was so strong is placed the computer at fresh risk.
The storm sent a cloud of superheated gas towards the planet at 2 million mph.
Such storms also hit Earth fairly regularly, and can affect GPS satellites and utility grids as well as causing beautiful auroras at the poles. It's also not unknown for flares to affect craft orbiting Mars: in 2003 a solar storm took out the radiation detector on the Odyssey orbiter.
As a result the $2.5 billion Curiosity rover was placed back in safe mode, and left to wait out the storm:
"We're being more careful," said project leader Richard Cook at Nasa.
Nasa has already speculated that the original glitch may have been caused by high-energy cosmic rays striking the computer.
Meanwhile the other Mars craft - the Opportunity rover and the two orbiting satellites - are said to be operating normally.
The rover is currently being used to analyse rock powder as part of a two-year search for the chemical ingredients of life.