by bystander » Wed Jan 09, 2013 11:57 pm
Nathan Bridges wrote:Climbing in Nereidum Montes (ESP_029608_1390) (video)
This image shows the southern part of a dune field in Nereidum Montes, which is being monitored for changes in dune and ripple positions.
Many of the dunes in this image are overlying steep slopes. The slopes are dipping to the south, yet the dunes, as evidenced by the north-facing orientation of their steep slip faces, are being blown upslope, to the north. Such "climbing dunes" have been found elsewhere on Mars, such as in Valles Marineris and in this case, indicate relatively strong southerly winds.
A close-up image shows one of these slip faces. In addition, several apparent landslide troughs are present. These are interpreted as sand that has slumped down the slope. Subsequently, the wind has remobilized some of the sand and formed climbing ripples within the troughs. This and other HiRISE images show the dynamic interplay between wind and gravity, two of many processes occurring on Mars today.
Alfred McEwen wrote:An Overflow Channel from Athabasca Vallis (ESP_029864_1880) (video)
A MOC image over this area showed a channel spilling out of the larger Athabasca Vallis (trending east-west at the north end of this image) and flowing to the south.
The channel splits into multiple branches, creating about ten streamlined mesas. Vague bumps were visible on the channel floor in the MOC image--perhaps large boulders that were deposited by floodwaters?
Our HiRISE image reveals the bumps to be rootless cones that form from lava-water interaction. The entire channel system appears to be coated by lava. There are two leading hypotheses for the origin of these channels: (1) they were carved by water and later coated by lava, or (2) the channels were eroded by the lava itself. If eroded by lava, a source of water was still needed to create the rootless cones, but could have been a much smaller quantity of water than that needed to carve the channels.
Credit: NASA/JPL/University of Arizona
<< Previous HiRISE Update[quote="Nathan Bridges"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_029608_1390.jpg[/img3][/float][url=http://www.uahirise.org/ESP_029608_1390][b][i]Climbing in Nereidum Montes (ESP_029608_1390)[/i][/b][/url] [b][i]([url=http://www.youtube.com/watch?v=kzaaOViv2OI]video[/url])[/i][/b]
This image shows the southern part of a dune field in Nereidum Montes, which is being monitored for changes in dune and ripple positions.
Many of the dunes in this image are overlying steep slopes. The slopes are dipping to the south, yet the dunes, as evidenced by the north-facing orientation of their steep slip faces, are being blown upslope, to the north. Such "climbing dunes" have been found elsewhere on Mars, such as in Valles Marineris and in this case, indicate relatively strong southerly winds.
[url=http://www.uahirise.org/images/2013/details/cut/ESP_029608_1390-1.jpg][b]A close-up image[/b][/url] shows one of these slip faces. In addition, several apparent landslide troughs are present. These are interpreted as sand that has slumped down the slope. Subsequently, the wind has remobilized some of the sand and formed climbing ripples within the troughs. This and other HiRISE images show the dynamic interplay between wind and gravity, two of many processes occurring on Mars today. [/quote]
[quote="Alfred McEwen"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_029864_1880.jpg[/img3][/float][url=http://www.uahirise.org/ESP_029864_1880][b][i]An Overflow Channel from Athabasca Vallis (ESP_029864_1880)[/i][/b][/url] [b][i]([url=http://www.youtube.com/watch?v=-dL1kTh8y_4]video[/url])[/i][/b]
A MOC image over this area showed a channel spilling out of the larger Athabasca Vallis (trending east-west at the north end of this image) and flowing to the south.
The channel splits into multiple branches, creating about ten streamlined mesas. Vague bumps were visible on the channel floor in the MOC image--perhaps large boulders that were deposited by floodwaters?
Our HiRISE image reveals the bumps to be rootless cones that form from lava-water interaction. The entire channel system appears to be coated by lava. There are two leading hypotheses for the origin of these channels: (1) they were carved by water and later coated by lava, or (2) the channels were eroded by the lava itself. If eroded by lava, a source of water was still needed to create the rootless cones, but could have been a much smaller quantity of water than that needed to carve the channels. [/quote]
[b][i]Credit: NASA/JPL/University of Arizona[/i][/b]
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