by bystander » Thu Aug 29, 2013 1:07 am
HiRISE Science Team wrote:Oxbows and Cutoffs in Idaeus Fossae (ESP_029054_2165)
As rivers age they can meander and occasionally these meanders get so pronounced that the river cuts off these curving loops at their narrow end leaving them as isolated as oxbow lakes.
The objective of this observation is to check for the presence of these features. At HiRISE resolution, we should be able to test for traces of former meandering river channels in what looks like an oxbow feature in images from lower-resolution cameras.
HiRISE Science Team wrote:Breaching a Crater Rim in Tartarus Montes (ESP_029072_2040)
In this image,
we can see a small notch in a crater rim with a well-formed channel. Lava appears to have flowed through this notch and filled in this approximately 10-kilometer (6-mile) diameter crater.
Obtaining another image of the same area at a different angle (what we then call a "stereo pair") can help us see this terrain in three dimensions and answer some questions about what happened here, e.g., is the high-lava mark consistent with the lava overtopping the exterior? Did the crater fill to the level of the lava outside?
This is a stereo pair with
ESP_028637_2040.
Nathan Bridges wrote:Migrating and Static Sand Ripples on Mars (ESP_032616_1275)
Having operated at Mars for more than seven years, MRO and the HiRISE camera continue to make new discoveries. One of these is that many sand dunes and ripples are moving, some at rates of several meters per year.
In this observation, a dune field in a Southern hemisphere crater was observed approximately one Mars year apart, first on 2 September 2011 and then again on 11 July 2013 (a year on Mars is 687 Earth days). By taking images at the same time of year, solar illumination angles are the same, so that subtle apparent changes can be linked to true displacement on the surface and not artifacts.
In these two images, there is little distortion (a digital elevation model would remove more distortion). Here, we focus on the
southern and northern part of two adjacent dunes.
With an animated image, the displacement of ripples on the dunes relative to nearby rocks and dark ripples are clearly visible. It seems that the ripples on the southern dune are moving northeast, while those on the northern dune are moving west, indicating complex winds in this area. The static dark ripples may be composed of larger grains than those in the dunes and are therefore harder to move.
In most areas of Mars, darker-toned ripples are more mobile than lighter ones. This area is different, demonstrating that continued imaging of the Martian surface results in new findings and revisions of ideas.
This is a stereo pair with
ESP_032748_1275.
Credit: NASA/JPL/University of Arizona
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[quote="HIRISE Science Team"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_017741_1745.jpg[/img3][/float][size=110][url=http://www.uahirise.org/ESP_017741_1745][b][i]Basin in the West Candor Chasma Layered Deposits (ESP_017741_1745)[/i][/b][/url][/size]
This basin in Ceti Mensa exposes [url=http://uahirise.org/images/2013/details/cut/ESP_017741_1745-1.jpg][b]concentric rings[/b][/url] in the sedimentary layers. Dark sand ripples and [url=http://uahirise.org/images/2013/details/cut/ESP_017741_1745-2.jpg][b]textures in the bedrock[/b][/url] suggesting wind scouring are also apparent.
Wind is a powerful, erosive force, transporting fine-grain sediments that can shape topography and expose darker material underneath the surface. One such feature of wind-scour on Mars is in Gale Crater, where scouring has created a [url=http://www.uahirise.org/PSP_009927_1750][b]stair-step pattern[/b][/url].
This is a stereo pair with [url=http://www.uahirise.org/PSP_009460_1745][b]PSP_009460_1745[/b][/url]. [/quote]
[quote="HiRISE Science Team"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_029054_2165.jpg[/img3][/float][size=110][url=http://www.uahirise.org/ESP_029054_2165][b][i]Oxbows and Cutoffs in Idaeus Fossae (ESP_029054_2165)[/i][/b][/url][/size]
As rivers age they can meander and occasionally these meanders get so pronounced that the river cuts off these curving loops at their narrow end leaving them as isolated as oxbow lakes.
The objective of this observation is to check for the presence of these features. At HiRISE resolution, we should be able to test for traces of former meandering river channels in what looks like an oxbow feature in images from lower-resolution cameras. [/quote]
[quote="HiRISE Science Team"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_029072_2040.jpg[/img3][/float][size=110][url=http://www.uahirise.org/ESP_029072_2040][b][i]Breaching a Crater Rim in Tartarus Montes (ESP_029072_2040)[/i][/b][/url][/size]
In this image, [url=http://uahirise.org/images/2013/details/cut/ESP_029072_2040.jpg][b]we can see a small notch[/b][/url] in a crater rim with a well-formed channel. Lava appears to have flowed through this notch and filled in this approximately 10-kilometer (6-mile) diameter crater.
Obtaining another image of the same area at a different angle (what we then call a "stereo pair") can help us see this terrain in three dimensions and answer some questions about what happened here, e.g., is the high-lava mark consistent with the lava overtopping the exterior? Did the crater fill to the level of the lava outside?
This is a stereo pair with [url=http://www.uahirise.org/ESP_028637_2040][b]ESP_028637_2040[/b][/url]. [/quote]
[quote="Nathan Bridges"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_032616_1275.jpg[/img3][/float][size=110][url=http://www.uahirise.org/ESP_032616_1275][b][i]Migrating and Static Sand Ripples on Mars (ESP_032616_1275)[/i][/b][/url][/size]
Having operated at Mars for more than seven years, MRO and the HiRISE camera continue to make new discoveries. One of these is that many sand dunes and ripples are moving, some at rates of several meters per year.
In this observation, a dune field in a Southern hemisphere crater was observed approximately one Mars year apart, first on 2 September 2011 and then again on 11 July 2013 (a year on Mars is 687 Earth days). By taking images at the same time of year, solar illumination angles are the same, so that subtle apparent changes can be linked to true displacement on the surface and not artifacts.
In these two images, there is little distortion (a digital elevation model would remove more distortion). Here, we focus on the [url=http://uahirise.org/images/2013/details/cut/ESP_032616_1275-1.jpg][b]southern and northern part[/b][/url] of two adjacent dunes. [url=http://uahirise.org/images/2013/details/cut/ESP_032616_1275-2.gif][b]With an animated image[/b][/url], the displacement of ripples on the dunes relative to nearby rocks and dark ripples are clearly visible. It seems that the ripples on the southern dune are moving northeast, while those on the northern dune are moving west, indicating complex winds in this area. The static dark ripples may be composed of larger grains than those in the dunes and are therefore harder to move.
In most areas of Mars, darker-toned ripples are more mobile than lighter ones. This area is different, demonstrating that continued imaging of the Martian surface results in new findings and revisions of ideas.
This is a stereo pair with [url=http://www.uahirise.org/ESP_032748_1275][b]ESP_032748_1275[/b][/url]. [/quote]
[b][i]Credit: NASA/JPL/University of Arizona[/i][/b]
[url=http://asterisk.apod.com/viewtopic.php?t=31968][size=85][b][i]<< Previous HiRISE Update[/i][/b][/size][/url]