The onset of Martian winter weather is taking its toll on NASA's rovers Spirit and Opportunity. Lower temperatures, shorter days and the steady accumulation of dust on the rovers' solar panels are gradually reducing the amount of work each can accomplish.
Opportunity, which is circling a large crater, has been hardest hit. It has been plagued throughout the mission by a heater switch that is stuck in the on position, draining away its power. It can now do no more than two hours of science each day.
Last week it was reprogrammed to go into a deep sleep mode each night, which cuts off power to the main electronics systems including the heater. This has more than doubled its useful daily work time but has endangered one of the rover's most productive instruments, the mini-Thermal Emission Spectrometer, which analyses rocks. Without heating, the instrument is unlikely to survive temperatures lower than -50 °C. Night time temperatures have already dropped to -46 °C.
Spirit has suffered occasional computer glitches, but has already travelled more than three-quarters of the 2.5 kilometres to the layered hills north of its landing site. In the next few weeks NASA will decide which way Spirit should head once it arrives at the hills.
But just how long the rovers can keep going is anyone's guess. The Martian midwinter falls in mid-September, after which the days will get longer and warmer. This is when Mars passes behind the sun, blocking communications and creating a natural break in the mission. If the rovers are still working when NASA tries to make contact again in late September, they could just run and run.
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18:00 07 October 2008
17:56 07 October 2008
