Mars Rover Struggles to Weather Severe Dust Storm
Saturday, July 21, 2007
The hardy Mars rover Opportunity is struggling to stay alive amid a severe and long-lasting Martian dust storm -- posing the greatest threat so far to the unexpectedly long-lived vehicle.
The series of dust storms has blocked 99 percent of the direct sunlight that the rover needs to generate power, and on Wednesday, the panels were generating only 148 watt hours -- barely enough to keep the vehicle functioning. Without power to warm its electronic instruments and computers, the rover would grind to a halt for good.
"We're rooting for our rovers to survive these storms, but they were never designed for conditions this intense," said Alan Stern, associate administrator of NASA's Science Mission Directorate.
The dust storms kicked up late last month just as Opportunity was poised to make a dramatic entry into the Victoria Crater -- the deepest and most intriguing descent either of the Mars rovers would be attempting. NASA scientists believe that the layered rocks exposed in the crater could tell them much about the history of Mars, and especially whether life forms ever existed there.
The Martian dust, which NASA scientists say is more like smoke than sand, has been blowing for more than a month. It is common for winds to kick up the dust in the Martian summer, but officials said that these storms are the worst they have witnessed and could continue for days or even weeks.
While Opportunity and its twin rover Spirit have both been affected by the dust, the region around Opportunity has borne the brunt of the storm. Some of the dust is on or near ground level, but the most harmful kind is high in the Martian atmosphere, where it is blocking the sunlight.
All driving and science observations by Opportunity were suspended some time ago, but the rover was still using more energy this week than its solar panels could generate.
"The only thing left to cut were some of the communication sessions," said John Callas, project manager for the rovers at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
On Wednesday, mission controllers sent commands instructing Opportunity not to communicate with Earth for two days -- the first time either rover has been told to skip transmissions for more than one day. NASA engineers believe that step could lower its daily energy use to less than 130 watt hours -- a little more than the electricity needed to run two 60-watt light bulbs for one hour each.
Opportunity and Spirit have survived on the harsh Martian surface far longer than anticipated. They landed in January 2004 and were expected to last 90 days. Instead, they have been exploring Mars for more than 1,080 days.
One reason they have functioned for so long is, ironically, that the winds of previous dust storms cleaned off the solar panels, enabling the rovers to continue generating power.
Reflecting the severity of the situation, a NASA release yesterday said that "a possible outcome of this storm is that one or both rovers could be damaged permanently or even disabled. Engineers will assess the capability of each rover after the storm clears."
NASA plans to launch another Mars lander mission next month. Called Phoenix, it is scheduled to land near the planet's icy North Pole next May. Unlike Opportunity and Spirit, however, Phoenix will remain stationary and dig down into the icy Martian soil.