May 28, 2011

Science of Spirit: Obituary of Mars’s robot geologist

Filed under: Cool, Gadgets, Inner Solar System, Mars, Space Exploration, Space Ships — bferrari @ 9:35 am
Spirit overhead self portrait

Spirit overhead self portrait

From surviving bouts of amnesia to an escape from a sandy dungeon, sometimes it seemed that NASA’s Mars rover Spirit had at least nine lives. But yesterday, after hearing not a peep since March 2010, NASA decided to cut communications with the rover, putting an end to a six-year Martian mission during which it travelled 7730.5 metres. Daredevil escapes aside, here we assess the scientific legacy of this robot geologist.

Spirit was part of a robotic duo, along with its twin Opportunity. One of the aims of their joint mission was to look for signs of water, and from the start Spirit helped to gather clues towards this goal.

The rover’s adventure began on 3 January 2004 when it landed safely in the 170-kilometre-wide Gusev crater in the Martian southern hemisphere, a location chosen because orbital images suggested Gusev might once have held a giant lake. By 12 January, using a mini-Thermal Emission Spectrometer (mTES) – an infrared instrument that indicated the composition of nearby soils and rocks – the rover had already beamed back images of minerals associated with water.

Once it had left its landing platform, Spirit set off on a 2.5-kilometre trek across Martian plains, a journey that revealed little but basaltic lava flows. But upon reaching the Columbia hills in July, the rover uncovered more evidence for water by comparing the mineral content of the plains with that of the hills.

In February 2005, it found more evidence of water in an outcrop of rock dubbed Peace that contained a lot of sulphur. Two possible formation mechanisms, both involving water, were suggested.

Aside from water, Spirit was also tasked with hunting for clues to the forces and events that shaped the development of the young Red Planet. Spirit’s ascent of Husband Hill in 2005 revealed a diversity of rocks and meteorites whose structure and high nickel content hinted at an explosive history.

Then, in September 2005, Spirit snapped a 3D panoramic view from the top of the hill, providing a unique view of “the geological promised land”. Almost a year later, in June 2006, Spirit went on to discover metallic meteorites, echoing a discovery found by its twin Opportunity the year before.

Spirit also made discoveries of an unplanned nature, including taking Mars’s temperature using its mTES, a feat not thought possible before the rover landed. Also unplanned was the length of Spirit’s active life: it was originally designed to last just a few months.

Spirit’s scientific abilities became severely limited in April 2009, when its wheels broke a thin surface crust and got stuck in loose sand. After months unsuccessfully trying to free the rover, NASA announced in January 2010 that it would remain a stationary mission.

Now, after 10 months of calling out to Spirit without response, NASA engineers have decided to end communications completely. Equipment and assets that the rover used are needed for the Mars Science Laboratory, aka Curiosity, due to launch towards the Red Planet next year.

There is however, a sliver of hope for Spirit. Dave Lavery, NASA’s programme executive for solar system exploration, says, “While we no longer believe there is a realistic probability of hearing from Spirit, the Deep Space Network may occasionally listen for any faint signals when the schedule permits.”

Meanwhile, Opportunity is still rolling across the surface of the Red Planet today.



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