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Last Updated: Friday, 16 January, 2004, 18:49 GMT
Spirit begins Mars science work
Spirit arm, Nasa
The Instrument Deployment Device gets down to work
The US space agency rover Spirit has begun studying the red soil of Mars.

On the first day after leaving its landing pad, the probe manoeuvred its mechanical arm to allow its microscopic imager to see the ground.

Spirit also joined Europe's Mars Express orbiter to image the atmosphere - the first international experiment conducted on another planet.

Spirit is a "mobile geologist" that will explore Gusev Crater on Mars for signs of water, past or present.

Size of salt

On Sol 13, the thirteenth Martian day the rover has been on the planet, Spirit completed yet another series of firsts.

Spirit and Opportunity: Nasa space robots' Mars exploration mission

One was to swing its mechanical arm, or Instrument Deployment Device, out in front of itself and down towards the ground.

The arm has four instruments on the end. One is a microscopic imager which viewed a patch of soil just nine centimetres across.

"This is the highest resolution by far we have ever seen Mars at," said Ken Herkenhoff, who is in charger of the imager.

He added: "We're able to see sand-sized objects - the size of table salt - and conglomerates of finer dust particles."

'Magic' surface

The "cakey" surface of Mars at Spirit's landing site has intrigued scientists ever since they saw the first images showing how the rover's landing bags had pleated the surface as they dragged over it.

It has become known as the "magic carpet" of Mars.

Spirit viewed from above

"There is probably some cohesive component keeping the soil particles together," said Bob Sullivan, a member of the science team. Researchers want to know if the adhesion is the result of electrostatic forces or some other process.

One tantalising theory is that the carpet may contain sticky salts created when water evaporated through the upper layer of soil.

"The other instruments on the arm will test these hypotheses," said Sullivan.

Over the weekend, Spirit will use two German-made instruments, its Mossbauer and Alpha Particle X-ray spectrometers, to analyse the minerals and chemistry of the Martian soil.

Flight correction

One other major first on Friday was the combined effort with Europe's newly arrived orbiter Mars Express to take a close look at the atmosphere.

Soil, Nasa
The best images of Martian soil ever obtained
Spirit looked up through the Martian "air" in the same location and at the same time as Mars Express was looking down.

"This was the first ever coordinated international observation of Mars," said mission manager Mark Adler. "We have the data down but we haven't analysed it yet."

Spirit will spend a few days parked in front of its lander pad before trundling off across Gusev Crater.

Spirit's twin, Opportunity, lands on 24 January on the opposite side of the planet.

Nasa reported on Friday that some final trajectory adjustments would be needed to bring the probe closer to its planned landing zone.




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