Mars Rover Opportunity Gets Green Light To Enter Crater

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Guy Webster (818) 354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
Donald Savage (202) 358-1547
NASA Headquarters, Washington, D.C.
NEWS RELEASE: 2004-142 June 4, 2004
Mars Rover Opportunity Gets Green Light To Enter Crater
NASA has decided the potential science value gained by sending
Opportunity into a martian impact crater likely outweighs the risk of
the intrepid explorer not being able to get back out.
Opportunity has been examining the rim of the stadium-sized "Endurance
Crater" since late May. The rover team used observations of the
depression to evaluate potential science benefits of entering the
crater and the traversability of its inner slopes.
The soonest Opportunity could enter Endurance is early next week. It
will drive to the top of a prospective entry-and-exit route on the
southern edge of the crater and make a final check of the slope. If
the route is no steeper than what recent testing runs at NASA's Jet
Propulsion Laboratory, Pasadena, Calif., suggest a rover can climb,
controllers plan to radio Opportunity the command to go into the
"This is a crucial and careful decision for the Mars Exploration
Rovers' extended mission," said Dr. Edward Weiler, NASA's associate
administrator for space science. "Layered rock exposures inside
Endurance Crater may add significantly to the story of a watery past
environment that Opportunity has already begun telling us. The
analysis just completed by the rover team shows likelihood that
Opportunity will be able to drive to a diagnostic rock exposure,
examine it, and then drive out of the crater. However, there's no
guarantee of getting out again, so we also considered what science
opportunities outside the crater would be forfeited if the rover
spends its remaining operational life inside the crater."
Opportunity and its twin, Spirit, successfully completed their primary
three-month missions on Mars in April.
At a rock outcrop in a small impact feature nicknamed, "Eagle Crater,"
where Opportunity first landed, the rover found small-scale rock
textures and evaporite mineral compositions testifying that a body of
salty water covered the site long ago.
The wet environment may have been a suitable habitat for life, if it
ever existed on Mars. However, only the uppermost layer of the
region's layered crust was exposed at Eagle Crater, not deeper layers
that could reveal what the environment was like earlier.
The rock layer seen at Eagle Crater appears at Endurance Crater, too.
At Endurance, though, it lies above exposures of thicker, older
layers, which are the main scientific temptation for sending
Opportunity inside the crater.
"Answering the question of what came before the evaporites is the most
significant scientific issue we can address with Opportunity at this
time," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y.,
principal investigator for the science instruments on both rovers.
"We've read the last chapter, the record of the final gasps of an
evaporating body of water. What came before? It could have been a
deep-water environment. It could have been sand dunes. It could have
been a volcano. Whatever we learn about that earlier period will help
us interpret the upper layer's evidence for a wet environment and
understand how the environment changed."
Richard Cook, project manager at JPL for the rovers, said that
reaching one exposure of the older rock layers inside Endurance
requires driving only about 5 to 7 meters (16 to 23 feet) into the
130-meter-diameter (140-yard-diameter) crater. The rover is on the rim
at that site, which had been dubbed "Karatepe."
"We'll take an incremental approach, edging our way down to the
target," Cook said. The plan is to use the tools on Opportunity's
robotic arm to analyze the exposed layers for several days, then drive
in reverse back up the slope and exit the crater. The slope between
the rim and the layered outcrop at Karatepe is about 25 degrees.
"We have done testing that says we can do 25 degrees, provided the
wheels are on a rock surface and not loose sand," Cook said. Engineers
and scientists on the rover team built a test surface mimicking the
rocks and sand seen in Opportunity's images of Endurance Crater. The
surface was tilted to 25 degrees, and a test rover climbed it. If
portions of the route to the outcrop turn out to be between 25 and 30
degrees, the team plans to proceed slowly and use Opportunity to
assess the amount of traction the rover is getting.
JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Exploration Rover project for NASA's Office of Space
Science, Washington, D.C. Images and additional information about the
project are available from JPL at
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and from Cornell University, Ithaca, N.Y., at
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They did tests on Earth. Wouldn't the lesser gravity on Mars (1/3 Earth normal) make it possible to climb steeper slopes, as the rover be only 1/3 of the weight, or did they lighten the simulation rover by removing stuff?
Reply to
Bart Declercq
It's more complicted than that. Soil doesn't hold together in exactly the same way it does on Earth. That is to say the angle of repose is slightly different.
--Chris Vancil
Reply to
CL Vancil
No, because as a result, it also has only 1/3 of the traction. (It would need only 1/3 as much *power* for the climb, but at the speed the rovers move, that's a lesser issue.)
If I recall correctly, to a first approximation, questions of *stability* (whether of the rover or the soil underneath it) are independent of gravity, because the major factors that influence stability scale up and down together as gravity changes.
Looked at more closely, that isn't quite true, because secondary issues which don't scale the same way have some influence.
A more important factor for Opportunity is that the properties of the soil under its wheels are not known very precisely. That introduces large uncertainties into any attempt to predict such things.
Reply to
Henry Spencer
I believe that news release states that they expect to go in and out of the creator on a rock surface. Didn't we have a discussion in this newsgroup (at nauseam) about traction in reduced gravity :-) I wonder why the plans have changed,they had said they were going to get other things done on the plains before going in,now it's seems like they want to get in there right away. Maybe the rovers power is more critical then what we previously thought.....
Reply to
"Henry Spencer" skrev i en meddelelse news:
That's my impression too
I'll guess that the spherules are the danger. Riding on solid rock should be safe, but a sudden slide on the spherules can bring the rover into unforeseeable situations.
I were a bit 'piqué' when some JPL staff member was prized for his ability to bring the missions into public attention - it made me, as a scientific observer, feel possibly manipulated by the choice of published material. I wonder weather the decision of going in is in part to catch a bit more public attention. It's non the less a courageous one that I look forward to follow. How much trouble do they get for loosing the rower in the attempt? I suspect that part of the problem in taking the decision is, that even in the crater, the rower will not be able to 'climb up' to the exposed profiles.
Does anyone by the way have an idea of how come the rock-surfaces are so plane. Is it a function of the very blast, or is it a later erosional feature. The topology and stratified nature of the crater-rim as seen in the profile seems to me to suggest a horizontal compression that 'thickened' the strata into an elevated rim more than the ejected material have made a build up on top of the familiar 'evaporitic' strata. Maybe the lack of ejected blocks next to the crater, more than anything else, gives a clue about the kind of blast that has taken place. Aren't these craters the first unique opportunity for the astro/planetary people to study a 'pristine' crater?
Reply to
Carsten Troelsgaard
that's what I thought the concern would be also the spherules.Like riding over hundreds of ball bearings on a slope,could be tricky !? I believe that Steve Squyres in the May 6th briefing said that all the layers were laid out there where the crater is the most easily accessible so there shouldn't be any trouble getting to all the layers.
Reply to
This is one advantage a legged robot will have over a wheeled one :)
Reply to
Larry O.
So let me get this straight-- the heatherns at NASA actually have the gall to send a robot INTO GOD?
Reply to
Darren Garrison
to send a robot INTO GOD?
Not a prayer.
Sir Charles W. Shults III
Reply to
Sir Charles W. Shults III
send a robot INTO GOD?
And back out again, if you'd believe it! And on a rock surface, no less!
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