Ageing Mars rover halts research, powers down in heavy dust storm

NASA’s solar-powered Opportunity Mars rover, seen here in an artist’s concept, has powered down and suspended science operations because of a widespread dust storm that has sharply reduced the energy reaching its solar cells. Image: NASA

NASA’s long-lived Opportunity Mars rover is hunkering down to conserve power in a bid to weather a huge dust storm blanketing the red planet that has, in effect, turned day into night for the solar-powered robot.

Science operations were suspended on 8 June, but a transmission received at the Jet Propulsion Laboratory in Pasadena, California, two days later showed the rover still had enough charge in its battery to phone home, a positive sign given the dust storm has been intensifying.

The opacity of the storm, an indication of how effectively it is blocking out sunlight, is at record levels for Opportunity, making it difficult for the rover’s solar arrays to fully charge its batteries. For comparison, a major 2007 dust storm had an opacity level, or tau, above 5.5 while the current storm had an estimated tau of 10.8 as of 6 June.

The most recent transmission from Opportunity “showed the rover’s temperature to be about minus 20 degrees Fahrenheit (minus 29 degrees Celsius),” NASA said in a status report. “One saving grace of dust storms is that they can actually limit the extreme temperature swings experienced on the Martian surface. The same swirling dust that blocks out sunlight also absorbs heat, raising the ambient temperature surrounding Opportunity.”

Program managers have requested additional communications coverage through NASA’s Deep Space Network to keep close tabs on the rover during its latest trial by dust.

Monitoring Opportunity’s power levels will indicate how successfully the rover is able to balance a lower-than-normal battery charge with the need to keep heaters operating to offset the frigid temperatures.

With a design life of 90 days, Opportunity landed on Mars in January 2004, three weeks after a twin rover – Spirit – touched down on the other side of the red planet. Both rovers vastly exceeded expectations and while Spirit, which got stuck in a sand dune, went off line in 2010, Opportunity continues to return valuable science.

But surviving the current dust storm could prove a major challenge for the ageing robot. Opportunity first detected the storm on 1 June and it has now grown to cover an area larger than North America, more than 18 million square kilometres (seven million square miles).

During the even more extensive 2007 dust storm, Opportunity spent two weeks in low power mode and was out of contact with Earth for several days. It is not yet clear low long the current storm might last.

“Full dust storms like this one are not surprising, but are infrequent,” NASA said in its status report. “They can crop up suddenly but last weeks, even months. During southern summer, sunlight warms dust particles, lifting them higher into the atmosphere and creating more wind. That wind kicks up yet more dust, creating a feedback loop that NASA scientists still seek to understand.”





The opacity of the dust