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Opportunity Turns Its Wheels

Twilight At Gusev
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    Here is the martian twilight sky at Gusev crater, as imaged by the panoramic camera on NASA's Mars Exploration Rover Spirit around 6:20 in the evening of the rover's 464th martian day, or sol (April 23, 2005).

    Spirit was commanded to stay awake briefly after sending that sol's data to Mars Odyssey at sunset. This small panorama of the western sky was obtained using camera's 750-nanometer, 530-nanometer and 430-nanometer color filters. This filter combination allows false color images to be generated that are similar to what a human would see, but with the colors exaggerated.

    In this image, the bluish glow in the sky above where the Sun had just set would be visible to us if we were there, but the redness of the sky farther from the sunset is exaggerated compared to the daytime colors of the martian sky. These kinds of images are beautiful and evocative, but they also have important scientific purposes. Specifically, twilight images are occasionally acquired by the science team to determine how high into the atmosphere the martian dust extends, and to look for dust or ice clouds.

    Other images have shown that the twilight glow remains visible, but increasingly fainter, for up to two hours before sunrise or after sunset. The long martian twilight compared to Earth's is caused by sunlight scattered around to the night side of the planet by abundant high altitude dust. Similar long twilights or extra-colorful sunrises and sunsets sometimes occur on Earth when tiny dust grains that are erupted from powerful volcanoes scatter light high in the atmosphere. These kinds of twilight images are also more sensitive to faint cloud structures, though none were detected when these images were acquired. Clouds have been rare at Gusev crater during Spirit's 16-month mission so far.

  • Ithica CA (JPL) May 17, 2005
    The Mars Rover teams have contunied their slow and methodical approach to getting their 400 million dollar robot out of a sand dune on Mars some 191 million kilometers away.

    Now, in his latest Mars Mission Update rover chief scientist Steven Squyres reports on the extraction process at Meridiani, which got underway on the weekend.

    "So far we've executed three sols worth of activity. On the first one we simply straightened the wheels, which worked fine. The next two sols were executed over the weekend, and each commanded two meters worth of wheel turns. We were pleased with the outcome of those, too.

    The rover moved more than a centimeter in the expected direction during each maneuver, which was just the kind of behavior we were hoping for. (In fact, the motion was actually more than I was personally expecting to see this early in the game.) We clearly moved some soil in the process, and there was an encouraging amount of clearing of caked-up debris from between cleats on some of the wheels.

    We'll be continuing to work at this over the coming week. Each day, for the next few days at least, we'll command some number of meters worth of wheel turns, based on the results we got from the prior sol.

    Today we chose 4 meters, based on the good progress that each of the 2-meter sols gave us over the weekend. After that we may keep it at 4 meters for awhile, drop it back to 2, or bump it up to something even higher, depending on what we see.

    Anyway, we're real pleased with the results so far, and we'll keep chugging away, bit by bit, until we're out.

    Over at Gusev, life is good. We've finished our work on Jibsheet, the composition and texture of which both fit nicely into an evolving story that we have on all the rocks here on Cumberland Ridge.

    With Jibsheet done, we're now planning a drive back toward Larry's Lookout. This will be a long one, at least by Columbia Hills standards, but since it's mostly downhill we expect it to go pretty quickly.

    The plan is to drive to a point that's on safe ground a few meters shy of the east side of the Lookout. There are some rocks there that lie stratigraphically older than anything we have seen yet... in fact, they may be the oldest rocks that we have yet seen at Gusev.

    We'll look at them from a safe distance first, and see what we see. After that, we've got some decisions to make. Back when we had lots of dust on the solar arrays, we had to get around to the south side of Husband Hill quickly or the rover would die.

    With clean arrays now, though, it's a different world, and we've got a lot of options. We're going to be making some very interesting strategic decisions with Spirit over the next couple of weeks.

    Steve Squryes mission updates are published by Cornell University and are updated on an ad hoc basis. To see the very latest news check in at Cornell's Athena Mars website.





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    Opportunity Rover Begins Careful Rollout
    Pasadena CA (JPL) May 15, 2005
    NASA's Mars Exploration Rover Opportunity rotated its wheels on sol 463 for the first time since the rover dug itself into a sand dune more than two weeks earlier.



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