The Mars Exploration Rovers Spirit and Opportunity landed on Mars on January 4, 2004 and January 25, 2004, respectively. Spirit continued operating until contact was lost on March 22, 2010, a total of 2,269 Earth days, which is 2,208 days on Mars (sols)1. Spirit operated on the Martian surface 24.5 times as long as its design life of 90 sols.
Even more amazing: Opportunity has been operating on the Martian surface (as of this publication date) for 5,108 Earth days, which is 4,971 sols. That’s 55.2 times its design life of 90 sols!
Spirit and Opportunity faced their greatest challenge up to that point during the global Martian dust storm of July 2007. Here is what I wrote about it back then.
Spirit and Opportunity‘s Greatest Challenge (7-26-07)
The intrepid Mars Exploration Rovers Spirit and Opportunity—which have been operating on the surface of Mars over 14 times longer than planned—each carry two 8 amp-hour lithium batteries, and these batteries are charged by solar panels. Before dust storms began significantly reducing the amount of sunlight reaching the rovers’ solar panels, they were generating about 700 watt-hours of electricity each day—enough to power a 100-watt light bulb for seven hours. Not much, it may seem, but plenty enough to operate each rover’s internal heaters, motors, scientific instruments, and communication equipment.
In recent weeks, both rovers have seriously been affected by the dust storms, particularly Opportunity which last week was able to generate only 128 watt-hours of electricity on the worst day. With precious little energy to replenish the internal batteries, controllers have hunkered down the rovers to conserve energy for the most critical need—internal heaters to keep the core electronics warm enough to operate. Remember, the average surface temperature on Mars is -85° F!
At press time, weather conditions appear to be improving for both rovers, but there are still worries that the rovers could have been damaged by all that dust blowing at them for days on end.
As it turns out, after the global dust storm of 2007 subsided, the rovers benefited from subsequent “cleaning events” where the winds of Mars blew most of the dust off of the solar panels.
There have been no global dust storms on Mars since 2007; however, another one is anticipated later this year. Hopefully, our intrepid Opportunity will weather the storm and continue to generate enough life-giving power from its precious solar panels .
1A Martian day is called a sol and is slightly longer than an Earth day. A mean solar day on Earth is 24h00m00s, by definition, but a mean solar day on Mars is 24h39m35.244s Earth time. To convert Earth days to Martian sols, divide the number of Earth days by 1.0275.