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This field of small dunes is located on the floor of an unnamed crater in the southern hemisphere of Mars.

Source: THEMIS - Mars Odyssey Mission

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The ridge in the center of this image occurs on the plains north of Reull Vallis. No other ridges occur in the region. The debris on the southern slope of the ridge has flow-type features which may indicate the ice is present.

Source: THEMIS - Mars Odyssey Mission

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The layering of the south polar cap is evident in this image.

Source: THEMIS - Mars Odyssey Mission

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This large landslide is located within an unnamed crater to the WSW of Holden Crater.

Source: THEMIS - Mars Odyssey Mission

Sharp Views Show Ground Ice on Mars Is Patchy and Variable

05.02.07

Using observations by NASA's Mars Odyssey orbiter, scientists have discovered that water ice lies at variable depths over small-scale patches on Mars.

The findings draw a much more detailed picture of underground ice on Mars than was previously available. They suggest that when NASA's next Mars mission, the Phoenix Mars Lander, starts digging to icy soil on an arctic plain in 2008, it might find the depth to the ice differs in trenches just a few feet apart. The new results appear in the May 3, 2007, issue of the journal Nature.


Image above: This color-coded map indicates the depth to icy layers at
a site in southern Mars. The dense, icy layer retains heat better than the
looser soil above it, so where the icy layer is closer to the surface, the
surface temperature changes more slowly than where the icy layer is
buried deeper.
Image credit: NASA/JPL/ASU

"We find the top layer of soil has a huge effect on the water ice in the ground," said Joshua Bandfield, a research specialist at Arizona State University, Tempe, and author of the paper. His findings come from data sent back to Earth by the Thermal Emission Imaging System camera on Mars Odyssey. The instrument takes images in five visual bands and 10 heat-sensing (infrared) ones.

The new results were made using infrared images of sites on far-northern and far-southern Mars, where buried water ice within an arm's length of the surface was found five years ago by the Gamma Ray Spectrometer suite of instruments on Mars Odyssey. The smallest patches detectable by those instruments are several hundred times larger than details detectable by the new method of mapping depth-to-ice, which sees differences over scales of a few hundred yards or meters.

The new approach uses thermal imaging as a thermometer to measure how fast the ground changes temperature during local spring, summer and fall. The dense, icy layer retains heat better than the looser soil above it, so where the icy layer is closer to the surface, the surface temperature changes more slowly than where the icy layer is buried deeper.

The resulting maps show that the nature of the surface soil makes a difference in how close to the surface the ice lies. Areas with many rocks at the surface, Bandfield explained, "pump a lot of heat into the ground and increase the depth where you'll find stable ice." In contrast, dusty areas tend to insulate the ice, allowing it to survive closer to the surface. "These two surface materials -- rock and dust -- vary widely across the ground, giving underground ice a patchy distribution," he said.

Computer models helped him interpret the temperature observations, he said. "They show areas where water ice would be only an inch or so under the soil, while in other areas ice could lie many feet below the surface."

The results fit long-term climatic models for Mars. These show the planet has been both warmer and colder in the past, similar to glacial cycles on Earth. Bandfield said, "The fact that ice is present near the depth of stability in the current Martian climate shows that the ground ice is responding to climate cycles." In turn, he added, this implies that water ice in the ground can swap places with water vapor in the atmosphere as the climate changes.

Philip Christensen of Arizona State University, Tempe, principal investigator for the Thermal Emission Imaging System, said, "Scientists have known for more than a decade that water is on Mars, mostly in the form of ice. What's exciting is finding out where the ice is in detail and how it got there. We've reached the next level of sophistication in our questions."

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, Calif., manages Mars Odyssey for NASA's Science Mission Directorate. Odyssey's Thermal Emission Imaging System is operated by Arizona State University. For additional information about Odyssey and the new findings, visit http://www.nasa.gov/mars and http://themis.asu.edu.


Media contacts: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

Robert Burnham 480-458-8207
Arizona State University, Tempe

2007-049

Source: NASA Missions - Mars Odyssey

Depth-to-Ice Map of an Arctic Site on Mars

05.02.07

Color coding in this map of a far-northern site on Mars indicates the change in nighttime ground-surface temperature between summer and fall. This site, like most of high-latitude Mars, has water ice mixed with soil near the surface. The ice is probably in a rock-hard frozen layer beneath a few centimeters or inches of looser, dry soil. The amount of temperature change at the surface likely corresponds to how close to the surface the icy material lies.

The dense, icy layer retains heat better than the looser soil above it, so where the icy layer is closer to the surface, the surface temperature changes more slowly than where the icy layer is buried deeper. On the map, areas of the surface that cooled more slowly between summer and autumn (interpreted as having the ice closer to the surface) are coded blue and green. Areas that cooled more quickly (interpreted as having more distance to the ice) are coded red and yellow.

The depth to the top of the icy layer estimated from these observations, as little as 5 centimeters (2 inches), matches modeling of where it would be if Mars has an active cycle of water being exchanged by diffusion between atmospheric water vapor and subsurface water ice.

This map and its interpretation are in a May 3, 2007, report in the journal Nature by Joshua Bandfield of Arizona State University, Tempe. The Thermal Emission Imaging System camera on NASA's Mars Odyssey orbiter collected the data presented in the map. The site is centered near 67.5 degrees north latitude, 132 degrees east longitude, in the Martian arctic plains called Vastitas Borealis. It was formerly a candidate landing site for NASA's Phoenix Mars Lander mission. This site is within the portion of the planet where, in 2002, the Gamma Ray Spectrometer suite of instruments on Mars Odyssey found evidence for water ice lying just below the surface. The information from the Gamma Ray Spectrometer is averaged over patches of ground hundreds of kilometers or miles wide. The information from the Thermal Emission Imaging System allows more than 100-fold higher resolution in mapping variations in the depth to ice.

The Thermal Emission Imaging System observed the site in infrared wavelengths during night time, providing surface-temperature information, once on March 13, 2005, during summer in Mars' northern hemisphere, and again on April 8, 2005, during autumn there. The colors on this map signify relative differences in how much the surface temperature changed between those two observations. Blue indicates the locations with the least change. Red indicates areas with most change. Modeling provides estimates that the range of temperature changes shown in this map corresponds to a range in depth-to-ice of 5 centimeters (2 inches) to more than 18 centimeters (more than 7 inches). The sensitivity of this method for estimating the depth is not good for depths greater than about 20 centimeters (8 inches).

The temperature-change data are overlaid on a mosaic of black-and-white, daytime images taken in visible-light wavelengths by the same camera, providing information about shapes in the landscape. The 10-kilometer scale bar is 6.2 miles long.

NASA's Jet Propulsion Laboratory manages the Mars Odyssey mission for NASA's Science Mission Directorate, Washington, D.C. The Thermal Emission Imaging System was developed by Arizona State University in collaboration with Raytheon Santa Barbara Remote Sensing. Lockheed Martin Space Systems, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

Image Credit: NASA/JPL/ASU

+ High resolution JPEG

Source: NASA Missions - Mars - Images

Depth-to-Ice Map of a Southern Mars Site Near Melea Planum

05.02.07

Color coding in this map of a far-southern site on Mars indicates the change in nighttime ground-surface temperature between summer and fall. This site, like most of high-latitude Mars, has water ice mixed with soil near the surface. The ice is probably in a rock-hard frozen layer beneath a few centimeters or inches of looser, dry soil. The amount of temperature change at the surface likely corresponds to how close to the surface the icy material lies.

The dense, icy layer retains heat better than the looser soil above it, so where the icy layer is closer to the surface, the surface temperature changes more slowly than where the icy layer is buried deeper. On the map, areas of the surface that cooled more slowly between summer and autumn (interpreted as having the ice closer to the surface) are coded blue and green. Areas that cooled more quickly (interpreted as having more distance to the ice) are coded red and yellow.

The depth to the top of the icy layer estimated from these observations suggests that in some areas, but not others, water is being exchanged by diffusion between atmospheric water vapor and subsurface water ice. Differences in what type of material lies above the ice appear to affect the depth to the ice. The area in this image with the greatest seasonal change in surface temperature corresponds to an area of sand dunes.

This map and its interpretation are in a May 3, 2007, report in the journal Nature by Joshua Bandfield of Arizona State University, Tempe. The Thermal Emission Imaging System camera on NASA's Mars Odyssey orbiter collected the data presented in the map. The site is centered near 67 degrees south latitude, 36.5 degrees east longitude, near a plain named Melea Planum. This site is within the portion of the planet where, in 2002, the Gamma Ray Spectrometer suite of instruments on Mars Odyssey found evidence for water ice lying just below the surface. The information from the Gamma Ray Spectrometer is averaged over patches of ground hundreds of kilometers or miles wide. The information from the Thermal Emission Imaging System allows more than 100-fold higher resolution in mapping variations in the depth to ice.

The Thermal Emission Imaging System observed the site in infrared wavelengths during night time, providing surface-temperature information. It did so once on Dec. 27, 2005, during late summer in Mars' southern hemisphere, and again on Jan. 22, 2006, the first day of autumn there. The colors on this map signify relative differences in how much the surface temperature changed between those two observations. Blue indicates the locations with the least change. Red indicates areas with most change. Modeling provides estimates that the range of temperature changes shown in this map corresponds to a range in depth-to-ice of less than 1 centimeter (0.4 inch) to more than 19 centimeters (more than 7.5 inches). The sensitivity of this method for estimating the depth is not good for depths greater than about 20 centimeters (8 inches).

The temperature-change data are overlaid on a mosaic of black-and-white, daytime images taken in infrared wavelengths by the same camera, providing information about shapes in the landscape. The 20-kilometer scale bar is 12.4 miles long.

NASA's Jet Propulsion Laboratory manages the Mars Odyssey mission for NASA's Science Mission Directorate, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University in collaboration with Raytheon Santa Barbara Remote Sensing. Lockheed Martin Space Systems, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

Image Credit: NASA/JPL/ASU

+ High resolution JPEG

Source: NASA Missions - Mars - Images

about time

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The dust storm season in the southern hemisphere of Mars is well underway. This image of an unnamed crater southeast of Hellas Basin shows the encroachment of a storm in the region.

Source: THEMIS - Mars Odyssey Mission

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This Image of the Day is the 1,200th posted since the series began March 27, 2002. It shows a strip of ground in the Daedalia Planum region of the giant volcanic provice of Tharsis.

The lava flows come from the Arsia Mons volcano. Its summit lies about 300 miles (500 kilometers) to the right of the image, which measures 11 miles (18 kilometers) wide by 39 miles (63 km) long.

The rough textured lava surface traps dust and sand, while the impact craters act as obstacles to the wind. The combination of readily available dust and turbulent winds passing the craters creates the bright and dark 'tails' extending to the west of the craters. These wind streaks indicate the wind was blowing from east to west (right to left).

Source: THEMIS - Mars Odyssey Mission

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Gullies dissect the crater rim and dunes cover part of the floor of the unnamed crater east of Russell Crater.

Source: THEMIS - Mars Odyssey Mission

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The highstanding material in this image are old, fractured lava flows. The fracturing created the maze-like western part of Valles Marineris called Noctis Labyrinthus. Younger lava flows from the Tharsis volcanos have filled the low areas.

Source: THEMIS - Mars Odyssey Mission

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This field of dunes in located of the floor of an unnamed crater north of Proctor Crater.

Source: THEMIS - Mars Odyssey Mission

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The vertical features that look like long puffy streamers in this image are actually the clouds at the margin of a large dust storm.

Source: THEMIS - Mars Odyssey Mission

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This image is located just outside the south polar cap region. The dark leaf-shaped features are material moving down slope and then down valley. Note that the broad end of the features are located over dark outcrops.

Source: THEMIS - Mars Odyssey Mission

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The floor of this unnamed crater east of Proctor Crater contains two types of dunes. To the north are coalescing small individual dunes. At the southern end of the group of small dunes there is a large linear dune that is becoming a sand sheet.

Source: THEMIS - Mars Odyssey Mission

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These small, bright, linear dunes are located on lava flows from Arsia Mons.

Source: THEMIS - Mars Odyssey Mission

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This image shows part of the Mangala Vallis channel system.

Source: THEMIS - Mars Odyssey Mission

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These small dunes are located on the rough floor of an unnamed crater next to the much larger Russell Crater. The bright material on the southern faces of the dunes is frost.

Source: THEMIS - Mars Odyssey Mission

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The rough and smooth lava flows in this image are part of the extensive flows from Arsia Mons.

Source: THEMIS - Mars Odyssey Mission

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The fractures at the top of this image are part of Mangala Fossae. The fractures in the lower half are part of the Memnonia Fossae system.

Source: THEMIS - Mars Odyssey Mission

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The windstreaks in this image are located of Arsia Mons lava flows in the Daedalia Planum region.

Source: THEMIS - Mars Odyssey Mission

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These small, dark dunes in Ruza Crater are moving from the crater floor to the crater rim. With the passage of time and continued wind activity the leading dunes will exit the crater completely.

Source: THEMIS - Mars Odyssey Mission

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These dust devil tracks are located in Noachis Terra, south of Proctor Crater.

Source: THEMIS - Mars Odyssey Mission

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This broad channel is located on the flank of Tyrrhena Patera, an old volcano in the southern hemisphere of Mars.

Source: THEMIS - Mars Odyssey Mission

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This sinuous ridge with an abrupt hook-shaped end is located in the south polar region.

Source: THEMIS - Mars Odyssey Mission

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These dark dunes are located on the floor of an unnamed crater north of Rabe Crater.

Source: THEMIS - Mars Odyssey Mission

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This images shows the edge of the south polar cap.

Source: THEMIS - Mars Odyssey Mission

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The fractures in this image are part of Memnonia Fossae. Large wrinkle ridges are being cut by the fractures.

Source: THEMIS - Mars Odyssey Mission

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This small field of dunes is located on the floor of an unnamed crater.

Source: THEMIS - Mars Odyssey Mission

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Only the tops of clouds of dust can be seen in this image. Southern spring is the time of dust storms, which typically start in the large Hellas and Argyre basins. This storm is located southwest of Hellas.

Source: THEMIS - Mars Odyssey Mission

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This dissected surface is located in highlands between Solis Planum and Aonia Terra. These channels were likely carved by running water.

Source: THEMIS - Mars Odyssey Mission

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This VIS image shows a small portion of the floor of Candor Chasma, part of Vallis Marineris. Different layers and textures are seen in this image.

Source: THEMIS - Mars Odyssey Mission

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This image shows part of Managala Vallis, including a streamlined island. The narrow tail of the island points downstream.

Source: THEMIS - Mars Odyssey Mission

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The landslide in this image occurs within Coprates Catena. The Catena parallels Vallis Marineris.

Source: THEMIS - Mars Odyssey Mission

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The small crater in this image is located bordering the much larger Oudemans Crater. The long landslide could have occurred during the formation of the small crater, or much later due to instabilities remaining after crater formation. Note the dust slide that continues downhill from the end of the landslide.

Source: THEMIS - Mars Odyssey Mission

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This infrared image covers a portion of the surface of Mars north of Proctor Crater. The sand dunes in the bottom of the crater at the top of the image show up bright in this daytime infrared image because they are warm. The dunes are dark in color. The THEMIS infrared camera is used to detect surface and atmospheric temperatures.

Source: THEMIS - Mars Odyssey Mission