Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2004 February 18 
Posted on 02/18/2004 5:04:05 AM PST by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2004 February 18
Explanation: The cloud poses no danger to the building. Appearing to float above a remote monastery in Sicily, Italy, the anvil cloud's shape shows several classic cloud features. The cloud itself is composed of millions of very small droplets of water and ice. The dramatically flat cloud bottom is caused by temperature falling in the lower atmosphere -- above a specific height water-saturated air is forced to condense out water droplets. The shape of the cloud middle is caused by the water-droplet-laden column of air being blown both upward and to one side. The anvil shape at the cloud top is likely caused by the upward air column reaching a stable atmospheric layer, likely the stratosphere, where horizontally moving air fans out the top of the cloud. The cumulonimbus cloud was captured out the front door of a house last year.
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.
 Opportunity dug this trench with its right front wheel. Credit: NASA/JPL/Ames |
"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.
 The brightness of the newly exposed soil is seen in this image taken by the rover's hazard-avoidance camera. The rock outcrop lining the inner edge of the small crater encircling the rover and lander can be seen on the horizon. Credit: NASA/JPL |
"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.
 This composite image maps the areas traveled by Opportunity at Meridiani Planum. Dotted lines represent areas the rover has already traveled. Solid lines represent areas still on the rover's travel agenda. Credit: JPL/NASA/Cornell/MSSS |
"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 to make."
Road trip to Bonneville Crater continues for Spirit
BY JUSTIN RAY
SPACEFLIGHT NOW
Posted: February 17, 2004
Proving to be a real Mars hotrod, the Spirit rover has become the most traveled vehicle on the Red Planet, surpassing the distance accumulated by the Pathfinder rover nearly seven years ago.
"We certainly knew that was likely to occur, but it is good to see that it did after about 45 days on the surface," Richard Cook, the newly named Mars Exploration Rover project manager, said Tuesday.
Pete Theisinger, project chief for the past few years, has been selected to manage NASA's nuclear-powered Mars Science Laboratory mission scheduled for launch in 2009.
 Spirit looking behind as its empty lander base and the tracks across the Martian surface. Credit: NASA/JPL Download a larger version of image here |
Spirit is heading to the impact crater nicknamed by scientists as Bonneville. Along the way, the rover is stopping to collect science data on rocks, tiny dunes and soil samples across the wind-swept Martian surface.
"We are doing robotic field geology," says Ray Arvidson, deputy principal investigator. "We are in the middle of a long set of drives with traverse science where we have started at the landing site and we are moving up to the rim of Bonneville Crater."
Mission officials elected to dispatch Spirit to the crater with the goal of studying rock layers and obtaining information about the planet's history, including the potential of a watery past.
"The idea is the impact crater would have overturned the stratigraphy and exposed it for our viewing pleasure," Arvidson said.
 This mosaic image from Spirit's panoramic camera shows a forward-looking view. Credit: NASA/JPL/Cornell Download a larger version of image here |
"It depends on what we find between where we are now and where we are going. We are looking for new materials to stop and to make detailed measurements of," Arvidson said.
"The focus is on the traverse science and getting to the rim of Bonneville over the next dozen or so sols (Martian days). We should get there expeditiously. The rate at which we get there depends on what we discover in terms of new materials. Then once we are on the rim and finish making measurements, then the issue becomes can we get into the crater? What are the slopes of the walls? Or should we head for the Southeast Hills?"
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I love this idea.
Thanks for bringing it to my attention.
And thanks for the ping to the APOD.
There's always something interesting here.
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