TAMPA (Florida) • A massive dust storm raging across Mars has overcome Nasa's ageing Opportunity rover, putting the unmanned, solar-powered vehicle into sleep mode and raising concerns about its survival, the US space agency says.
The unusually severe dust storm has blocked out the Sun over a quarter of the Red Planet, blanketing an area spanning 35 million sq km, Nasa explained on Wednesday.
Opportunity, located in a spot called Perseverance Valley, "has fallen asleep and is waiting out the storm", said Mr John Callas, Opportunity project manager at Nasa's Jet Propulsion Laboratory. "We are concerned but we are hopeful that the storm will clear and the rover will be able to communicate with us."
The storm was first detected on May 30, and grew worse in recent days. The robotic vehicle - one of two currently operating on Mars - has shut everything down except its master clock, and last communicated with Earth on June 10.
Mr Callas declared a "spacecraft emergency" due to low power.
"In this point we are in a waiting mode. We are listening every day for possible signals from the rover," he said, likening the atmosphere among colleagues to having a loved one lying in a coma.
"If it was your 97-year-old grandmother, you would be very concerned. And we are," he said.
Opportunity, along with its twin named Spirit, was launched in 2003 and landed on Mars a year later to hunt for signs of past life. Its mission was meant to last just 90 days.
The rover "has made a number of discoveries about the Red Planet including dramatic evidence that long ago at least one area of Mars stayed wet for an extended period and that conditions could have been suitable for sustaining microbial life," Nasa said in a statement.
When the storm struck, Opportunity was tooling around near a channel to see if it might have been created by flowing water, wind erosion, or something else. Its partner rover, Spirit, became stuck in soft soil in 2009, and its mission was formally declared over in 2011.
Opportunity is expected to remain asleep until there is enough power to charge the battery above a certain threshold, at which point it would autonomously wake up, said Mr Callas.