by bystander » Wed Mar 13, 2013 9:39 pm
Colin Dundas wrote:Recent Gully Activity on Mars (ESP_020661_1440)
Gully landforms like those in this image are found in many craters in the mid-latitudes of Mars. Changes in gullies were first seen in images from the Mars Orbiter Camera in 2006, and studying such activity has been a high priority for HiRISE. Many examples of new deposits in gullies are now known.
This image shows a new deposit in Gasa Crater, in the Southern mid-latitudes. The deposit is
distinctively blue in enhanced-color images. This image was acquired in southern spring, but the flow that formed the deposit occurred in the preceding winter.
Current gully activity appears to be concentrated in winter and early spring, and may be caused by the seasonal carbon dioxide frost that is visible in gully alcoves in the winter.
Shane Byrne wrote:A Crater Gets Torn in Half (ESP_030559_2135)
Planetary surfaces can be very complex and record many different events and modifications. Scientists try to reconstruct the history of these surfaces by looking to see how features overlap.
In this image you can see a circular impact crater about 2 kilometers (1.25 miles) across. Cutting through the crater is a trench running from the top of the image to the bottom. Geologists call these trenches "graben," which actually means trench in German. They are formed when the surface stretches apart to the left and right forming cracks. When these cracks open a block of rock can drop downwards, this block is the flat floor of the trench you see here.
In this case, the crater existed first before the graben formed. Half of the crater rim is sitting on the trench floor while the other half remains on the surrounding high ground. Despite being torn in two by the graben, both halves of the crater are in pristine condition indicating that these features are all geologically young.
Nathan Bridges wrote:Colorful Gully Walls in Terra Sirenum (ESP_030667_1395)
Gullies are found on many slopes in the middle and near-polar latitudes of Mars. Although they contain no liquid water today, whether and how much water may have been involved in their formation, and any water's origin, is a matter of considerable debate.
The gullies appear relatively young, so a current process, perhaps involving ground ice or condensed volatiles--water or carbon dioxide--may be at work. Regardless, HiRISE images provide insight on gully origins and processes.
In this image, we see gullies within two craters in Terra Sirenum.
One closeup shows gully alcoves touching a crater wall. Dark sand fills the alcoves and scattered boulders are apparent. Some bright rocks on the gully walls are visible, perhaps exposed by the processes that carved the gullies.
Another closeup shows gullies that are much larger than those to the north. Intriguing yellowish colors are visible on some of the walls. Determing whether this represents chemical alteration of the walls by water, or exposed, unaltered bright rock, will require further study.
Colin Dundas wrote:Eastern Rim of Endeavour Crater (ESP_030872_1775)
Endeavour Crater is a large impact crater formed on Mars billions of years ago. Erosion and burial have filled in the depression and reduced the rim to a broken-up ring of hills made of rock that is older than the surrounding plains.
The Mars Exploration Rover (MER) Opportunity is currently exploring the west rim of the crater, and studying new types of rock that are very different from anything seen earlier in the mission. HiRISE images of the rest of the crater help the MER team plan their operations and understand how particular sites visited by the rover fit into the big picture.
Credit: NASA/JPL/University of Arizona
<< Previous HiRISE Update[quote="Colin Dundas"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_020661_1440.jpg[/img3][/float][size=110][url=http://www.uahirise.org/ESP_020661_1440][b][i]Recent Gully Activity on Mars (ESP_020661_1440)[/i][/b][/url] [/size]
Gully landforms like those in this image are found in many craters in the mid-latitudes of Mars. Changes in gullies were first seen in images from the Mars Orbiter Camera in 2006, and studying such activity has been a high priority for HiRISE. Many examples of new deposits in gullies are now known.
This image shows a new deposit in Gasa Crater, in the Southern mid-latitudes. The deposit is [url=http://www.uahirise.org/images/2013/details/cut/ESP_020661_1440.jpg][b]distinctively blue in enhanced-color images[/b][/url]. This image was acquired in southern spring, but the flow that formed the deposit occurred in the preceding winter.
Current gully activity appears to be concentrated in winter and early spring, and may be caused by the seasonal carbon dioxide frost that is visible in gully alcoves in the winter. [/quote]
[quote="Shane Byrne"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_030559_2135.jpg[/img3][/float][size=110][url=http://www.uahirise.org/ESP_030559_2135][b][i]A Crater Gets Torn in Half (ESP_030559_2135)[/i][/b][/url] [/size]
Planetary surfaces can be very complex and record many different events and modifications. Scientists try to reconstruct the history of these surfaces by looking to see how features overlap.
In this image you can see a circular impact crater about 2 kilometers (1.25 miles) across. Cutting through the crater is a trench running from the top of the image to the bottom. Geologists call these trenches "graben," which actually means trench in German. They are formed when the surface stretches apart to the left and right forming cracks. When these cracks open a block of rock can drop downwards, this block is the flat floor of the trench you see here.
In this case, the crater existed first before the graben formed. Half of the crater rim is sitting on the trench floor while the other half remains on the surrounding high ground. Despite being torn in two by the graben, both halves of the crater are in pristine condition indicating that these features are all geologically young. [/quote]
[quote="Nathan Bridges"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_030667_1395.jpg[/img3][/float][size=110][url=http://www.uahirise.org/ESP_030667_1395][b][i]Colorful Gully Walls in Terra Sirenum (ESP_030667_1395)[/i][/b][/url] [/size]
Gullies are found on many slopes in the middle and near-polar latitudes of Mars. Although they contain no liquid water today, whether and how much water may have been involved in their formation, and any water's origin, is a matter of considerable debate.
The gullies appear relatively young, so a current process, perhaps involving ground ice or condensed volatiles--water or carbon dioxide--may be at work. Regardless, HiRISE images provide insight on gully origins and processes.
[url=http://www.uahirise.org/images/2013/details/cut/ESP_030667_1395-1.jpg][b]In this image[/b][/url], we see gullies within two craters in Terra Sirenum. [url=http://www.uahirise.org/images/2013/details/cut/ESP_030667_1395-2.jpg][b]One closeup[/b][/url] shows gully alcoves touching a crater wall. Dark sand fills the alcoves and scattered boulders are apparent. Some bright rocks on the gully walls are visible, perhaps exposed by the processes that carved the gullies.
[url=http://www.uahirise.org/images/2013/details/cut/ESP_030667_1395-3.jpg][b]Another closeup[/b][/url] shows gullies that are much larger than those to the north. Intriguing yellowish colors are visible on some of the walls. Determing whether this represents chemical alteration of the walls by water, or exposed, unaltered bright rock, will require further study. [/quote]
[quote="Colin Dundas"][float=left][img3=""]http://www.uahirise.org/images/wallpaper/800/ESP_030872_1775.jpg[/img3][/float][size=110][url=http://www.uahirise.org/ESP_030872_1775][b][i]Eastern Rim of Endeavour Crater (ESP_030872_1775)[/i][/b][/url] [/size]
Endeavour Crater is a large impact crater formed on Mars billions of years ago. Erosion and burial have filled in the depression and reduced the rim to a broken-up ring of hills made of rock that is older than the surrounding plains.
The Mars Exploration Rover (MER) Opportunity is currently exploring the west rim of the crater, and studying new types of rock that are very different from anything seen earlier in the mission. HiRISE images of the rest of the crater help the MER team plan their operations and understand how particular sites visited by the rover fit into the big picture. [/quote]
[b][i]Credit: NASA/JPL/University of Arizona[/i][/b]
[url=http://asterisk.apod.com/viewtopic.php?t=30817][size=85][b][i]<< Previous HiRISE Update[/i][/b][/size][/url]