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Last Updated: Tuesday, 13 January, 2004, 20:10 GMT
Mars rover to visit deep crater
Spirit and Opportunity: Nasa space robots' Mars exploration mission

The US space agency Nasa has unveiled a list of targets on the Martian surface which it plans to explore using its robot rover Spirit.

Areas earmarked for investigation include a nearby crater, where a meteorite may have exposed some of Mars's mysterious underground geology.

The rover will then proceed toward distant hills to learn more about the processes that shaped Mars.

Spirit should leave its landing pad to roll on to the surface on Thursday GMT.

"We know where we are now and we also know where we're going," Cornell University scientist Steve Squyres told a news conference.

"With that knowledge we can now intelligently plan a mission-long traverse, a mission-long plan of exploration for this landing site."

Mission objectives

Scientists decided on the plan following analysis of the terrain using radio techniques and photographic data from the rover.

"The goal of this [mission] is to find materials that will tell us whether or not Gusev Crater once contained a lake and what the conditions were like in that lake," said Professor Squyres.

"We will soon know what the material we are on is like, but what lies beneath that? And what's higher up? Those are the questions we'd like to answer by traversing."

We know where we are now and we also know where we're going
Steve Squyres, Cornell University
Spirit will first carry out analysis of nearby rocks strewn about its landing site.

Following that, it will investigate a crater 200 metres (656 feet) across that lies 250 m (820 ft) to the north-east of Spirit's current position.

"This is an extremely attractive target. It will have dug down to a depth of tens of metres. It will probably have a rim that might be - I don't know what - three, four, five metres high," said Professor Squyres.

He explained that he did not know what tasks Spirit would carry out when it finally got to the crater.

But as Spirit gets closer to the crater's edge, it will move into the "ejecta blanket" - the material thrown out perhaps from 30 metres (98 feet) below the surface by the impact of the meteorite.

"It will provide a window into the sub-surface of Mars," said Professor Squyres.

"After we've done that, we will have seen as deep into Mars as we can ever hope to see in this mission. That's the biggest crater that's accessible to us."

Mission scientist Tim Parker said the profile of the crater had been partially buried or stripped away, perhaps either by the action of water or wind.

"The interior is certainly not as deep as a fresh bowl-shaped crater is, relative to its diameter," he explained.

Head for the hills

After this, the rover will head towards the "eastern hills" that can be seen in the distance from Spirit's Gusev Crater landing site. But these hills are some 3,000 m (2 miles) from Spirit's current position. The rover was only designed to travel 600 metres (2,000 feet) from its initial position.

There are no firm plans to go as far as the hills, but it is hoped that the rover will come across rocks that originated in them as it goes closer to them.

This will give scientists a reference point with which to compare the other rocks from the Gusev Crater and allow them to determine whether water once swilled around in this Martian basin.

Spirit has fired a pyrotechnic device to cut the last umbilical cable that shackled it to the landing pad and is now free to position itself for "egress" or to roll three metres on to the Martian surface.

Scientists also revealed that the rover bounced 28 times on its landing and may have encountered updrafts of wind as it touched down.

Mars infographic

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