Opportunity digs Mars
BY JUSTIN RAY
Posted: February 17, 2004
The Mars Exploration Rover Opportunity is putting its mark on the Red Planet, digging a small hole so its suite of science instruments can probe soil enriched with hematite, a mineral that typically forms in the presence of water.
"We dug a nice big hole on Mars," rover planner Jeffrey Biesiadecki quipped during a news conference Tuesday.
Using its right front wheel, the craft carved a trench 10 centimeters (4 inches) deep, 20 centimeters (8 inches) wide and 50 centimeters (20 inches) long.
"We start with the right front wheel digging by itself, turning half of a degree in the negative direction, digging a small pile of material in front of it, and we image that with the front (hazard avoidance cameras) so we can see the initial scraping of material that we dig up in the first move.
"Then the rover will turn-in-place to its right about 12 degrees followed by another running of the right front wheel all by itself, this time in the opposition direction, kicking up material behind the wheel.
"It will turn-in-place back to the left, going a little bit further than where it started from, again running the right front wheel in the reverse direction, increasing the pile that is forming.
"It continues this process over and over again as long as we let it, growing a wider and deeper trench as it goes.
"On each end before we reverse direction, the rover will actually drive onto the pile of material that is forming on each side and that's to compress and compact that material so it doesn't slide back down into the hole we are digging.
"Finally, as we are driving from one end to the other we have the rover pause in the middle of the trench. It stops, runs the right front wheel again by itself, kicks up material in the direction it is traveling, drives over that material and kicks it up again towards the side of the trench. This is to prevent a mound from forming in the middle of the trench. This extra scraping in the middle helps reduce the size of that mound."
The wheel digging took six minutes, but that time was actually spread out over 22 minutes. The rover took breaks between spins to snap images and allow its motors to cool down and prevent overheating.
"What we are looking at is the mineralogy, the chemistry (and) the texture of the undisturbed surface and the surface where material is excavated," said Ray Arvidson, rover deputy principal investigator.
Initial pictures of the trench have already grabbed scientists' curiosity.
"Some of the things catching the attention of the science team include the clotty nature of the soil seen along the upper walls as well as the contrast in brightness -- from the brighter floor material with the material outside the trench," said Rob Sullivan, science team member from Cornell University.
The instruments on Opportunity's arm -- the Alpha Particle X-Ray Spectrometer, Mossbauer Spectrometer and Microscopic Imager -- will be studying the hole over the next couple of days. The rover also will take images with its other cameras.
"In the next couple of days we will be getting these results in. We should be getting better images to look at as well," Sullivan said.
"Why are we here? Earlier, Mini-TES had looked around the interior of the crater that we are in and found that the area that the rover has currently driven to is richer in hematite than other places," Sullivan said.
Once finished examining the trench, Opportunity will drive back to the exposed bedrock along the crater wall for science work, including using its Rock Abrasion Tool (RAT) to drill into the outcropping.
"The intent is to move to El Capitan, which is back to the wall rocks and do a full suite of measurements including pre- and post-RAT'ing on the key outcrops," Arvidson said.
"And after that, we will exit the crater and probably drive to the crater that is approximately 600 meters to our east. The idea there is to do a radial ejecta traverse, very similar to what we are doing with (Spirit at) Bonneville. But that is all being debated and it is subject to the exploration and discovery that we expect make."
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