[meteorite-list] At The Mouth of the Red Valley (Mars Express)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 14 Feb 2013 12:23:38 -0800 (PST)
Message-ID: <201302142023.r1EKNcCp025147_at_zagami.jpl.nasa.gov>

http://www.esa.int/Our_Activities/Space_Science/At_the_mouth_of_the_red_valley
    
At the mouth of the red valley
European Space Agency
14 February 2013

[Image]

ESA's Mars Express took a high-resolution stereo image on 13
January of the southeast corner of the Amenthes Planum region on
Mars, near to Palos crater and the mouth of a well-known sinuous
valley, Tinto Vallis.

At the bottom-centre of the full-colour image above, and up close
in the first perspective image, is a nearby shorter and wider
valley, which is fed by a number of tributaries before it joins
the mouth of Tinto Vallis as both empty into Palos crater, just
off the bottom of the image.

The 190 km-long Tinto Vallis is seen in the context image and is
named after the famous Rio Tinto river in the Andalucia region of
Spain. It is believed to have formed around 3.7 billion years ago,
during the early history of Mars.

[Image]
Valley feeding Palos Crater

The network of shorter valleys shown in the first perspective
image is thought to have formed through volcanic activity melting
subsurface ice and liberating water to the martian surface via
seeps and springs.

If underground water emerges to the surface from the side of a
slope - a process that planetary geologists call "groundwater
sapping" - it weakens the ground above it, causing it to collapse.
Over time, this process may lead to the formation of steep-sided
U-shaped valleys.

Groundwater sapping is believed to be responsible for erosion seen
in many of the valley networks on the Red Planet.

[Image]
Amenthes Planum in context

Another eye-catching feature is the relatively deep 35 km-wide
crater seen in the left-hand portion of the colour, topographic
and 3D images. Spectacular landslides along the crater's walls can
be seen and are particularly evident along the broken southern
(left) rim.

This crater sits on top of at least three older craters, the
largest of which is 100 km wide and dominates the whole top left
half of the 2D and 3D anaglyph images. The western rim of this
crater continues beyond the image frame, and can be more easily
distinguished in the context image.

[Image]
Amenthes Planum topography

The floor of this 100 km-wide crater is chaotic, with flat-topped
geological features called mesas, and their smaller siblings,
buttes, littering the floor. These are probably the result of the
removal of subsurface water ice leading to the collapse of weaker
material around them, leaving these more resistant high-sided
features behind.

On Earth, the desert regions in Utah are home to many examples of
these types of formation.

[Image]
Trough feeding Amenthes Planum

Toward the north (right) side of the 2D images, several smaller
craters display very smooth and flat floors, from infilling by
sediments.

The darker regions to the far north and south shown most clearly
in the first colour image are covered in wind-transported basaltic
sands.

The smooth low-lying region to the far right and shown in the
second perspective image is a small trough that feeds into the
broader lava field of Amenthes Planum. The trough has likely been
modified by the outflow of material from the ancient lake that may
have once existed in Palos crater, the rim of which can only just
be seen at the bottom of the colour, topographic and 3D images.

This smooth, channel-like feature brushes against the rim of a 30
km-wide crater, and both have been covered with dark wind-blown
materials.

[Image]
Amenthes Planum in 3D

With these recent images, Mars Express continues to show the
similarities between regions on Mars with those on our home planet.
Received on Thu 14 Feb 2013 03:23:38 PM PST