أخدود (المريخ)

أخاديد في المرتفعات الجنوبية في المريخ، جنوب أنگير پلانيتيا. صورة التقطها كامير هيريس على مارس ريكونيسانس أوربيتر.

أخاديد المريخ Martian gullies، هي شبكات صغيرة متبترة من القنوات الضيقة والمنحدرات الرسوبية المرتبطة بها، عُثر عليها على كوكب المريخ. سميت على اسم شبيهاتها من الأخاديد الأرضية. أكتشفت لأول مرة في صور التقطها مساح المريخ العالمي، وتقع على المنحدرات، خاصة على جدران الحفر.قد يكون عاد لكل أخدود كوة تصريف على رأسه، ومئزر مروحي الشكل عند قاعدته، ومجرى فردي من القنوات يصل بين الأخدودين، مما يعطي الأخدود بالكامل شكل الساعة الرملية. يقدر حتى عمر هذه الأخاديد صغير نسبياً لأن بها عدد قليل من الحفر، إذا وجدت. كما تم العثور على مجموعة فرعية من الأخاديد قبالة الكثبان الرملية، والتي تعتبر في حد ذاتها صغيرة صغيرة العمر نسبياً.

التشكل

Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Since there are no craters on this gully, it is thought to be rather young. Picture was taken by HiRISE under HiWish program. Location is Phaethontis quadrangle.

Group of gullies on north wall of crater that lies west of the crater Newton. The alcove and apron of one gully are labelled. These gullies are associated with moraine-like ridges at their downslope ends, which suggests they have formed at the site of a now-absent flowing ice. Note that they are cut into a mantle, which is much smoother than the rough-textured underlying material. Image taken by Mars Global Surveyor.

Gullies on wall of crater, as seen by HiRISE under HiWish program Location is the Mare Acidalium quadrangle.
Close-up of gully channels, as seen by HiRISE under HiWish program. This image shows many streamlined forms and some benches along a channel. These features suggest formation by running water. Benches are usually formed when the water level goes down a bit and stays at that level for a time. Picture was taken with HiRISE under HiWish program. Location is the Mare Acidalium quadrangle. Note this is an enlargement of a previous image.
Gullies in crater in Phaethontis quadrangle, as seen by HiRISE under HiWish program
Close-up of channels in gullies showing that the paths of the channels changed over time. This feature suggest formation by running water with a high load of sediment. Picture was taken with HiRISE under HiWish program. Location is the Mare Acidalium quadrangle. Note this is an enlargement of a previous image in Phaethontis quadrangle.
Gullies in crater, as seen by HiRISE under HiWish program. Location is Eridania quadrangle.
Close up of gullies in crater showing channels within larger valleys and curves in channels. These characteristics suggest they were made by flowing water. Note: this is an enlargement of the previous image by HiRISE under HiWish program. Location is Eridania quadrangle.
Close up of gully network showing branched channels and curves; these characteristics suggest creation by a fluid. Note: this is an enlargement of a previous wide view of gullies in a crater, as seen by HiRISE under HiWish program. Location is Eridania quadrangle.

المياه الجوفية

CTX image of the next image showing a wide view of the area. Since the hill is isolated it would be difficult for an aquifer to develop. Rectangle shows the approximate location of the next image.
Gully on mound as seen by Mars Global Surveyor, under the MOC Public Targeting Program. Images of gullies on isolated peaks, like this one, are difficult to explain with the theory of water coming from aquifers because aquifers need large collecting areas.
CTX image of part of Ross Crater showing context for next image from HiRISE.
Gullies in Ross Crater, as seen by HiRISE under the HiWish program. Because the gullies are on the narrow rim of a crater and they start at different heights, this example is not consistent with the model of gullies being caused by aquifers.
Gullies in two levels of a crater wall, as seen by HiRISE under HiWish program. Gullies at two levels suggests they were not made with an aquifer, as was first suggested. Location is Phaethontis quadrangle.
Lohse Crater Gullies on Central Peak. Image located in Argyre quadrangle. Having gullies on a central peak runs counter to the idea that they were formed by an aquifer, as was first suggested.

كثافة السلوج

انصهار الجليد الأرضي

أحدث التغيرات في الأخاديد

كيفية تغير آثار الإنحدار على المناخ

The straight on rays of the sun prevent snow from accumulating in mid-latitude craters when the tilt of Mars is high.

Shade on the pole-facing wall of a mid-latitude crater promotes snow accumulation. Note the snow will be grey to black due to dust.
By winter a large mass of snow has accumulated in the pole-facing pole of a crater. As the seasons warm, this snow deposit will melt to produce gullies.

Sharp-featured recent gullies (blue arrows) and older degraded gullies (gold) in the same location on Mars. These suggest cyclical climate change within the last two million years

صور الأخاديد

Group of gullies on north wall of crater that lies west of the crater Newton (41.3047 degrees south latitude, 192.89 east longitide). Image taken with Mars Global Surveyor under the MOC Public Targeting Program.
Atlantis Chaos, as seen by HiRISE. Click on image to see mantle covering and possible gullies. The two images are different parts of the original image. They have different scales.
Gullies. Notice how channels curve around obstacles, as seen by HiRISE.
MOLA context image for the series of three images to follow of gullies in a trough and nearby crater.
Gullies in a trough and nearby crater, as seen by HiRISE under the HiWish program. Scale bar is 500 meters long.
Close-up of gullies in crater, as seen by HiRISE under the HiWish program.
Close-up of gullies in trough, as seen by HiRISE under the HiWish program. These are some of the smaller gullies visible on Mars.
Gullies near Newton Crater, as seen by HiRISE, under the HiWish program. Place where there was an old glacier is labeled.
HiRISE image, taken under HiWish program, of gullies in a crater in Terra Sirenum.
Gullies with remains of a former glacier in crater in Terra Sirenum, as seen by HiRISE under HiWish program.
Gullies near Newton Crater, as seen by HiRISE under the HiWish Program.
Gullies in a crater in Terra Sirenum, as seen by HiRISE under the HiWish Program.
Close-up of gully showing multiple channels and patterned ground, as seen by HiRISE under the HiWish program.
Gullies in crater in Phaethontis quadrangle, as seen by HiRISE under HiWish program
Close-up of channels in gullies showing that the paths of the channels changed over time. This feature suggest formation by running water with a high load of sediment. Picture was taken with HiRISE under HiWish program. Location is the Mare Acidalium quadrangle. Note this is an enlargement of a previous image in Phaethontis quadrangle.

Gullies in a crater in Eridania, north of the large crater Kepler. Also, features that may be remains of old glaciers are present. One, to the right, has the shape of a tongue. Image taken with Mars Global Surveyor under the MOC Public Targeting Program.
HiRISE image showing gullies. The scale bar is 500 meters. Picture taken under the HiWish program.
Gullies and layers in mantle on a wall, as seen by HiRISE under HiWish program. Location is Eridania quadrangle.
Gullies, as seen by HiRISE under HiWish program.
Close-up of some gullies from previous image, as seen by HiRISE under HiWish program.
Close-up of apron on one of the gullies from previous image. Image was taken by HiRISE, under the HiWish program
Gullies on two different levels in crater, as seen by HiRISE under HiWish program

Jezza Crater,as seen by HiRISE. North wall (at top) has gullies. Dark lines are dust devil tracks. Scale bar is 500 meters long.
Scene in Argyre quadrangle with gullies, alluvival fans, and hollows, as seen by HiRISE under HiWish program. Enlargements of parts of this image are below.
Several levels of alluvial fans, as seen by HiRISE under HiWish program. Locations of these fans are indicated in the previous image.
Gullies in Nereidum Montes, as seen by HiRISE under HiWish program.
Wide view of gullies in Arkhangelsky Crater, as seen by HiRISE under HiWish program
Close-up of small channels in gullies in Arkhangelsky Crater, as seen by HiRISE under HiWish program Patterned ground in the shape of polygons can be seen to the right. Note: this is an enlargement of the previous image from Arkhangelsky Crater.
Close-up of a gully showing a channel going across the apron, as seen by HiRISE under HiWish program. Note: this is an enlargement of a previous image from Arkhangelsky Crater.

Group of gullies, as seen by HiRISE under the HiWish program.
Enlargement of part of previous image showing smaller gullies inside larger ones. Water probably flowed in these gullies more than once.

Gullies and massive flow of material, as seen by HiRISE under HiWish program. Gullies are enlarged in next two images. Location is Bamberg crater.
Close up view of some gullies, as seen by HiRISE under the HiWish program.
Close up view of another gully in same HiRISE picture. Picture taken under HiWish program.
Gullies, as seen by HiRISE under HiWish program.
Gullies in a crater, as seen by HiRISE under HiWish program.
Close-up of gullies in a crater from previous image. Image taken by HiRISE under HiWish program.
Gullies on wall of crater, as seen by HiRISE under HiWish program Location is the Mare Acidalium quadrangle.
Close-up of gully channels, as seen by HiRISE under HiWish program. This image shows many streamlined forms and some benches along a channel. These features suggest formation by running water. Benches are usually formed when the water level goes down a bit and stays at that level for a time. Picture was taken with HiRISE under HiWish program. Location is the Mare Acidalium quadrangle. Note this is an enlargement of a previous image.

A variety of gullies originating at different levels are visible in this HiRISE image that was taken under the HiWish program.
This enlargement of a small part of the previous image shows terraces along a gully channel. The terraces were created when a new channel cut through the old surface. This means that the gully was not in a single event. Water must have flowed more than once in this location.
Gullies in a crater. Some seem to be young, others are well developed. Picture was taken by HiRISE under the HiWish program.

Wide view of group of gullies, as seen by HiRISE under HiWish program. Note that part of this image is enlarged in the following image.
Close-up of gullies, as seen by HiRISE under HiWish program.

أخدود نواكيس الرباعي

Gullies on the wall of a crater, as seen by HiRISE under HiWish program
Gullies on mound in Asimov Crater, as seen by HiRISE.

أخدود كاسيوس الرباعي

Gullies in crater, as seen by HiRISE under HiWish program

انظر أيضاً

أرگير الرباعي
مناخ المريخ
إريدانيا الرباعي
جيولوجيا المريخ
فايثونتيس الرباعي
ثوماسيا الرباعي
المياه على المريخ

المصادر

^ Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.
^ G. Jouannic, J.Gargani, F. Costard, G. Ori, C. Marmo, F. Schmidt, A. Lucas (2012). "Morphological and mechanical characterization of gullies in a periglacial environment : The case of the Russell crater dune (Mars)". Planetary and Space Science. 71: 38–54.CS1 maint: multiple names: authors list (link)

وصلات خارجية

VEDIE et al., 2008 : Laboratory simulations of martian gullies on the Russel crater sand dunes <http://www.agu.org/pubs/crossref/2008/2008GL035638.shtml>
[1] Gives a general review of many of the theories involving the origin of gullies.
Dickson, J; Head, J; Kreslavsky, M (2007). "Martian gullies in the southern mid-latitudes of Mars: Evidence for climate-controlled formation of young fluvial features based upon local and global topography" (PDF). Icarus. 188: 315–323. Bibcode:2007Icar..188..315D. doi:10.1016/j.icarus.2006.11.020. Gives a good review of the history of the discovery of gullies.