NASA鈥檚 Mars rover Spirit will soon begin to trundle towards a slope on which it will try to ride out the coming winter 鈥� its third on the Red Planet. The slope will help maximise the sunlight reaching the rover鈥檚 power-producing solar panels, which are still coated with dust from a global dust storm that darkened the planet鈥檚 skies for much of July and August.
For months, Spirit has been exploring a 90-metre-wide raised plateau called Home Plate that was likely formed by an ancient, explosive volcanic eruption (see image at right).
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But winter is approaching in the planet鈥檚 southern hemisphere, where the rover is, so mission scientists have been searching for northern-tilting slopes that would allow Spirit to soak up the most sunlight, ensuring its power stays above the minimum needed.
They had considered some nearby sites that offered slopes of 20掳, but now, they have decided to send the rover about 60 metres away, to the northern end of Home Plate, which boasts steeper slopes of 25掳. That extra 5掳 of tilt will provide the rover with an extra 10 watt-hours of power per Martian day, says project manager John Callas in an online update. 鈥淸It] can mean the difference between surviving and not surviving the cold, dark winter.鈥�
The extra power is especially important because Spirit鈥檚 solar panels are still coated with dust from widespread dust storms that arose in late June and didn鈥檛 abate until August. 鈥淩ight now we鈥檝e got a really dirty rover,鈥� says rover chief scientist Steve Squyres of Cornell University in Ithaca, New York, US.
鈥淎nd we can鈥檛 count on a gust of wind to wipe it off,鈥� he adds, explaining that the region of Mars where Spirit is exploring usually has no wind, although there are occasional strong gusts. The situation is very different at its twin Opportunity鈥檚 site on the opposite side of the planet 鈥� there, lots of little wind gusts are constantly cleaning the rover.
Sprint south
The mission team hopes to have Spirit safely ensconced on its winter slope by 1 January 2008. 鈥淗ow long we need to be there depends on what kind of tilt we can achieve and whether we can get lucky with wind gusts,鈥� says Squyres. 鈥淚n the worst case, we have to be in place eight months or something.鈥�
After the winter, the team hopes to send Spirit 鈥渟printing to the south鈥� to some intriguing geological features that lie beyond Home Plate, Squyres says. These include a steep-sided mesa nicknamed 鈥榲on Braun鈥� whose top is resistant to erosion, and a 鈥渃razy looking鈥� hole in the ground called Goddard that may have been created by a volcanic explosion.
Meanwhile, on the other side of Mars, Opportunity is carefully scrutinising layers of rock inside the 800-metre-wide Victoria Crater. The meteorite impact that gouged out Victoria crater exposed layers of bedrock 30 metres deep, about six times deeper than anything the rover has had the chance to examine before.
The top part of the exposed rock is made up of three distinct layers, and Opportunity is now studying the second of those layers. 鈥淥ne hypothesis is that the lower layer has been soaked in water to a greater extent than the other ones,鈥� Squyres told New 杏吧原创 (see Surging groundwater solves Martian evaporite mystery). 鈥淲e鈥檒l see what Mars tells us.鈥�
Instrument problems
Opportunity will look for clues about how big a role ground water played at the site by digging into the rock with its rock abrasion tool (RAT) and studying its chemistry with the Alpha Particle X-Ray Spectrometer.
It will not be able to study its surroundings with its infrared spectrometer, however, because too much dust has accumulated on the mirror used to point the instrument 鈥� a problem mission members are trying to solve.
Fortunately, Squyres says it will not have much impact on the rover鈥檚 ability to do science, as the infrared spectrometer is a 鈥渂road brush鈥� instrument that may have already done all it can in the region. 鈥淲e鈥檙e to the point now where the interesting things we鈥檙e looking for [are] way down into the subtleties of this rock,鈥� he says.
Such instrument problems are getting increasingly common on the rovers, which landed on the planet in January 2004. 鈥淭hese rovers are getting old, and we鈥檙e having to get more and more clever to keep them going,鈥� says Squyres.
Mars Rovers 鈥� Mars is full of surprises; learn more in our continually updated .
