[meteorite-list] One Mars Rover Gets Stuck In, The Other Chills Out

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Jun 2 00:07:16 2006
Message-ID: <200606012055.NAA20845_at_zagami.jpl.nasa.gov>

http://www.newscientistspace.com/article/dn9253-one-mars-rover-gets-stuck-in-the-other-chills-out.html

One Mars rover gets stuck in, the other chills out
Maggie McKee
New Scientist
01 June 2006

The Mars rover Opportunity is working to free itself from a patch of
loose soil it got stuck in on Monday. But rover scientists are hopeful
it will escape relatively easily, since it got out of a similar
predicament last year simply by spinning its wheels backwards.

The rover was attempting to drive along a trough between the crests of
ripples in the Martian soil when it got stuck. But it is not mired as
deeply as it was in April 2005, when it was trapped for about five weeks
on a 30-centimetre-high ripple of soil, nicknamed "Purgatory Dune".

"At Purgatory, all six wheels were just about completely buried," says
Steve Squyres, principal investigator for the rovers and a planetary
scientist at Cornell University in New York, US. This time, only the
rover's rear wheels are buried deeply.

That is because the rover team implemented periodic "slip checks" after
the prolonged stay at Purgatory. These checks stop the wheels from
turning if onboard cameras show the rover has not moved as much as
expected based on the number of times the wheels have turned.

In this case, Opportunity was meant to have driven for 24 metres, but
ended up travelling just 1.5 m. "The rover detected a problem and
terminated the drive, which is why we didn't get in any deeper than we
did," Squyres told New Scientist.

Quick and easy

The Purgatory experience also led mission managers to develop a
successful escape mechanism. "Essentially you just drive the wheels
continuously in the opposite direction," says Squyres. "With each
rotation, the treads on the wheels move sand from in front of the wheel
to behind it - and slowly you work your way out."

Commands for the escape were due to be transmitted to the trapped rover
at about 0130 GMT on Thursday. Ray Arvidson, the mission's deputy
principal investigator and a planetary scientist at Washington
University at St Louis, US, is confident: "I think we'll pop out
relatively quickly."

If the rover does extricate itself, mission managers want to study the
area where it got trapped. "We're going to carefully assess the geometry
of this sand trap to figure out why this one got us," Squyres says.

All going well, the rover will continue its drive south towards a gaping
800-metre-wide crater called Victoria, which it has been targeting for
more than a year. The rover had been making treks of about 30 m per day
before it got stuck, and Victoria still lies about 900 m away.

"We have been driving the vehicle pretty aggressively for some time now,
and we will continue to push as hard as we can," Squyres told New Scientist.

Soaking up the sun

Meanwhile, on the other side of the planet, the Spirit rover is also
stuck in one place - but this time by design. Because it is in the midst
of the local winter on Mars, Spirit is subsisting on just 320 watt-hours
of solar power, compared to the 900 watt-hours it boasted after landing
in January 2004.

The rover is trying to maximise the light it receives by sitting on a
slope tilted 11? to the north, towards the Sun. "We're just sitting
there, enjoying what little sunshine we can get," Arvidson told New
Scientist.

But the rover is making the best of its situation, taking measurements
of the rock and soil beneath it and the sky overhead. It is also just
over halfway through making a 360? panorama of its surroundings with all
13 of its colour filters. Called McMurdo, the panorama will be a
"phenomenal data set", says Arvidson.

Spirit is expected to remain immobile through to August, after which it
may rotate its position to study some bedrock currently beyond the reach
of its robotic arm. But it will probably not begin driving again until
late 2006, when the local Martian winter ends.
Received on Thu 01 Jun 2006 04:55:11 PM PDT