by bystander » Wed Oct 03, 2012 7:17 pm
Eldar Noe wrote:Remnants of a Viscous Flow on Mars (ESP_028352_2245)
Lobate flows are common in the Martian mid latitude region (30-45 degrees latitude). Some are pristine-looking and highly reminiscent of terrestrial glaciers, whereas others appear more degraded. The flow deposit shown here is a good example of a degraded flow deposit.
The uphill "head" toward the right of the image has carved out an amphitheater-shape into the escarpment, and the "toe", to the right, is lobate in shape. The surface is highly degraded and eroded, and the deposit shows evidence of deflation (loss of volume, probably from the sublimation of ice), as lateral moraines (ridges running along the length of the feature) are visible.
Lazslo Kestay wrote:Ancient Layers on Mars (ESP_028487_2180)
This image shows the details of layers that were identified in previous lower resolution images. The terrain is along the boundary between the ancient highlands and the younger lowlands of Mars.
There are many erosional channels in this area, some of which expose layers. These geologic layers should be like pages in a book, telling us the story of how this part of Mars formed.
However, at HiRISE resolution it is clear that the surface has been reworked by small impact craters, dust, and ice processes. The result is that the pages are covered up by these later events. This is a common story across much of Mars. The more recent geologic activity has covered the ancient story of a possible warmer wetter past and one must dig into the subsurface to get to the distant past.
Ingrid Daubar wrote:Slope Streak Details and a New Streak (ESP_028642_1800)
Slope streaks are small, dark (occasionally bright) marks visible in many dusty areas on Mars. Some people have proposed that they are the traces of liquid water, but most scientists think that they form when very thin layers of fine dust is disturbed and slides downhill.
Fine details of these streaks can only be seen by HiRISE - for example,
the streak on the right encountered a crater as it moved downhill, leaving gaps below it where the dark streak did not continue. Why might it have been interrupted by that crater, but the streak on the left was not interrupted by either crater in its midst? The right streak also seems to follow along the ridges at the south end, traveling up the sides a little, but not overtopping them. What could that tell us about the material that is moving downhill, or its speed? There are also faint markings inside the streaks that run parallel to the streak edges - maybe this is another clue as to how they form.
Take a look at where all the streaks start in this image (slope streaks usually start at a point and widen as they move downhill, so that will also tell you which direction is downhill in this scene). Many of them start
at a small outcrop of a rocky layer. Perhaps falling rocks from those steep hills initiated the dust avalanches that formed the streaks.
Since this is what we call a monitoring image, we can also compare it with past images of the same spot. In this case,
at least one new slope streak has formed in the last five years! Studying repeated images of the same spot like this can tell us how often new streaks form, how old streaks are, and how they brighten over time.
Alfred McEwen wrote:Colorful Layers Exposed in the Walls of an Impact Crater (ESP_028693_1535)
This image covers most of an impact crater about 6 to 7 kilometers wide. Partway down from the crater rim is a prominent bright layer of bedrock.
The
full-resolution color data shows three distinct bedrock colors: yellow, light blue-green, and dark blue (in enhanced infrared colors). (North is down in the cutout, so the crater rim is near the top, which helps my brain to interpret the geometry.) These layers must correspond to different types of rock that were deposited as nearly flat-lying sheets, perhaps a combination of lava flows and sediments.
The relatively blue colors in HiRISE infrared color often correspond to minerals like olivine and pyroxene that are common in lava.
Credit: NASA/JPL/University of Arizona
<< Previous HiRISE Update[quote="Eldar Noe"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_028352_2245.jpg[/img3][/float][url=http://www.uahirise.org/ESP_028352_2245][b][i]Remnants of a Viscous Flow on Mars (ESP_028352_2245)[/i][/b][/url]
Lobate flows are common in the Martian mid latitude region (30-45 degrees latitude). Some are pristine-looking and highly reminiscent of terrestrial glaciers, whereas others appear more degraded. The flow deposit shown here is a good example of a degraded flow deposit.
[url=http://www.uahirise.org/images/2012/details/cut/ESP_028352_2245.jpg][b]The uphill "head" toward the right[/b][/url] of the image has carved out an amphitheater-shape into the escarpment, and the "toe", to the right, is lobate in shape. The surface is highly degraded and eroded, and the deposit shows evidence of deflation (loss of volume, probably from the sublimation of ice), as lateral moraines (ridges running along the length of the feature) are visible. [/quote]
[quote="Lazslo Kestay"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_028487_2180.jpg[/img3][/float][url=http://www.uahirise.org/ESP_028487_2180][b][i]Ancient Layers on Mars (ESP_028487_2180)[/i][/b][/url]
This image shows the details of layers that were identified in previous lower resolution images. The terrain is along the boundary between the ancient highlands and the younger lowlands of Mars.
There are many erosional channels in this area, some of which expose layers. These geologic layers should be like pages in a book, telling us the story of how this part of Mars formed.
However, at HiRISE resolution it is clear that the surface has been reworked by small impact craters, dust, and ice processes. The result is that the pages are covered up by these later events. This is a common story across much of Mars. The more recent geologic activity has covered the ancient story of a possible warmer wetter past and one must dig into the subsurface to get to the distant past. [/quote]
[quote="Ingrid Daubar"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_028642_1800.jpg[/img3][/float][url=http://www.uahirise.org/ESP_028642_1800][b][i]Slope Streak Details and a New Streak (ESP_028642_1800)[/i][/b][/url]
Slope streaks are small, dark (occasionally bright) marks visible in many dusty areas on Mars. Some people have proposed that they are the traces of liquid water, but most scientists think that they form when very thin layers of fine dust is disturbed and slides downhill.
Fine details of these streaks can only be seen by HiRISE - for example, [url=http://www.uahirise.org/images/2012/details/cut/ESP_028642_1800-1.jpg][b]the streak on the right[/b][/url] encountered a crater as it moved downhill, leaving gaps below it where the dark streak did not continue. Why might it have been interrupted by that crater, but the streak on the left was not interrupted by either crater in its midst? The right streak also seems to follow along the ridges at the south end, traveling up the sides a little, but not overtopping them. What could that tell us about the material that is moving downhill, or its speed? There are also faint markings inside the streaks that run parallel to the streak edges - maybe this is another clue as to how they form.
Take a look at where all the streaks start in this image (slope streaks usually start at a point and widen as they move downhill, so that will also tell you which direction is downhill in this scene). Many of them start [url=http://www.uahirise.org/images/2012/details/cut/ESP_028642_1800-2.jpg][b]at a small outcrop of a rocky layer[/b][/url]. Perhaps falling rocks from those steep hills initiated the dust avalanches that formed the streaks.
Since this is what we call a monitoring image, we can also compare it with past images of the same spot. In this case, [url=http://www.uahirise.org/images/2012/details/cut/ESP_028642_1800-3.jpg][b]at least one new slope streak[/b][/url] has formed in the last five years! Studying repeated images of the same spot like this can tell us how often new streaks form, how old streaks are, and how they brighten over time. [/quote]
[quote="Alfred McEwen"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_028693_1535.jpg[/img3][/float][url=http://www.uahirise.org/ESP_028693_1535][b][i]Colorful Layers Exposed in the Walls of an Impact Crater (ESP_028693_1535)[/i][/b][/url]
This image covers most of an impact crater about 6 to 7 kilometers wide. Partway down from the crater rim is a prominent bright layer of bedrock.
The [url=http://www.uahirise.org/images/2012/details/cut/ESP_028693_1535.jpg][b]full-resolution color data[/b][/url] shows three distinct bedrock colors: yellow, light blue-green, and dark blue (in enhanced infrared colors). (North is down in the cutout, so the crater rim is near the top, which helps my brain to interpret the geometry.) These layers must correspond to different types of rock that were deposited as nearly flat-lying sheets, perhaps a combination of lava flows and sediments.
The relatively blue colors in HiRISE infrared color often correspond to minerals like olivine and pyroxene that are common in lava. [/quote]
[b][i]Credit: NASA/JPL/University of Arizona[/i][/b]
[url=http://asterisk.apod.com/viewtopic.php?t=29629][size=85][b][i]<< Previous HiRISE Update[/i][/b][/size][/url]