[meteorite-list] Mars Express Image: Crater Dunes in Argyre Planitia / BARKHANE

From: Michel Franco <michel_at_meteoritecentral.com>
Date: Tue Aug 24 10:41:27 2004
Message-ID: <00e701c489e8$68865ab0$0201a8c0_at_cailloubi12zzr>

Hello Ron and List

Astonishing photo !

FYI: Barkhane are isolated structures.

here is a free translation of "Glossaire de geomorphologie", by Fernand
Joly ;

Metric dunes ( 10 meters high or over ) with a cressent shaped convex
up-wind smooth slope and steeper and concave downwind slope. Mobile in the
wind bed, it progresses with its horn on front. When they are not symetric,
with a longer horn, they are called "elb". ( plural alab) .
The word barkhane come from Turkestan.

 Isolated crescent-shaped sand dune lying transverse to the direction of the
prevailing wind, wings or horns of the crescent pointing downwind, and a
steep concave leeward slope inside the horns. ( mix compilation of different
european sources)

Usually barkane are found in fields with numerous individual not touching
each other. Higher barkhanes in the world are reported in the Gobi desert
with 60 meters.
Many barkhane fields in Western Sahara, not far from the coast in the
Laayoune area ( For those who travel this country, they are nicer a bit on
the south, say 70 km north of Dakhla. ) ( 15 to 20 metrs high.)

Here is a link of barkhanes on Mars
http://www.msss.com/mars_images/moc/3_11_99_nili/. Please note that some are
already forming a system in coalescence, i.e. mixing together.

and a photo of a typical planet earth barkhane

http://www.tec.army.mil/research/products/desert_guide/images/p165.gif shows
a complex barkhane with stripped convex side.

my two cents.

Best regards


----- Original Message -----
From: "Ron Baalke" <baalke_at_zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list_at_meteoritecentral.com>
Sent: Monday, August 23, 2004 10:31 PM
Subject: [meteorite-list] Mars Express Image: Crater Dunes in Argyre

> http://www.esa.int/export/SPECIALS/Mars_Express/SEMYRSW4QWD_0.html
> Crater dunes in Argyre Planitia
> European Space Agency
> Mars Express
> 23 August 2004
> These images, taken by the High Resolution Stereo Camera (HRSC) on board
> ESA's Mars Express spacecraft, show a Martian crater with a dune field
> on its floor.
> The images were taken during orbit 427 in May 2004, and show the crater
> with a dune field located in the north-western part of the Argyre
> Planitia crater basin.
> The images are centred at Mars longitude 303? East and latitude 43?
> South. The image resolution is approximately 16.2 metres per pixel.
> Crater dunes in 3D
> The crater is about 45 kilometres wide and 2 kilometres deep. In the
> north-eastern part of this crater, the complex dune field is 7
> kilometres wide by 12 kilometres long.
> In arid zones on Earth, these features are called ?barchanes?, which are
> dunes having an asymmetrical profile, with a gentle slope on the
> wind-facing side and a steep slope on the lee-side.
> The dune field shown here suggests an easterly wind direction with its
> steeper western part. The composition of the dune material is not
> certain, but the dark sands could be of basaltic origin.
> Crater dunes
> The colour image has been created from the HRSC?s nadir (vertical view)
> and three colour channels. The 3D anaglyph image has been created using
> the nadir and stereo channels.
> The perspective views have been calculated from the digital terrain
> model derived from the stereo channels.
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Received on Tue 24 Aug 2004 10:41:14 AM PDT

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