[meteorite-list] Mars Express: A Radiating Beauty on Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 5 Sep 2013 11:59:00 -0700 (PDT)
Message-ID: <201309051859.r85Ix0xS006060_at_zagami.jpl.nasa.gov>

http://www.esa.int/Our_Activities/Space_Science/Mars_Express/A_radiating_beauty_on_Mars

A radiating beauty on Mars
European Space Agency
5 September 2013

Exceptional structures deposited and shaped by water and winds
adorn these interlocking craters and sculpt radiating patterns in
the sands of Mars.

[Image]
Becquerel crater in context

This mosaic, which focuses on Becquerel crater in Arabia Terra, is
composed of four images taken by the high-resolution stereo camera
on ESA's Mars Express. Arabia Terra is in the transition zone
between the southern highlands and the northern lowlands of Mars.

Becquerel crater is named for the 19th-century French physicist
Antoine Henri Becquerel (1852-1908), winner of the Nobel Prize in
physics in 1903 along with Marie and Pierre Curie for the
discovery of radioactivity.

It is the largest crater in this scene, with a diameter of 167 km,
and drops to a depth of about 3.5 km below the surrounding
terrain. A second large crater lies within Becquerel, punching
even deeper into the surface, as seen in the Mars Express
topography and 3D images.

[Image]
Becquerel crater topography

The perspective view below reveals an intriguing, large mound
within Becquerel's crater walls, reminiscent of Mount Sharp in
Gale crater, currently being explored by NASA's Curiosity rover.

The mound rises about 1 km above the crater floor and comprises
hundreds of layers of light-toned sediments, each just a few
metres thick, made of sulphate-bearing rocks. On Earth, sulphates
are most often formed via the evaporation of water, so the
presence of these minerals in Becquerel crater suggests that water
may once have pooled here in a vast crater lake, before
evaporating away.

[Image]
Layered mound inside Becquerel crater

It is likely that the entire crater floor was once covered with
such sediments, but over billions of years much of it has been
eroded away by wind, leaving just a polished, rounded mound behind.

Similar light-toned sulphate-bearing deposits are seen all over
Arabia Terra, including in the crater walls in this scene,
pointing to a large-scale process that affected the entire region.

One popular theory is that large changes in the tilt of the
rotational axis of Mars leads to significant changes in its
climate, reflected in the thickness and repeating patterns found
in the layers of sediment. A change in the environmental
conditions would affect the way in which the sediments were
initially deposited, as well as their subsequent resistance to
erosion.

The deposits were laid down 3.8-3.5 billion years ago, at a time
when Mars was evolving from a warm, wet world into the cold and
dry planet we see today.

[Image]
Wind-blown sediments around Becquerel crater

Although water may no longer flow on the Red Planet, wind still
plays a key role in shaping the environment. Dark dunes and
wind-blown sediments streak through this scene, in vivid contrast
to the bright mound.

Rather than having originated locally, the dark material inside
Becquerel crater likely blew in from elsewhere - perhaps even from
volcanic eruptions.

A dark streak seems to drag the material out from the craters in a
wide swath towards the upper left of the main colour image (bottom
right of the perspective view above). A number of tiny craters
with tail-like structures lie along this track: their raised rims
influence the flow of wind over them such that the material
immediately downwind of the crater remains undisturbed in
comparison to the surrounding, exposed plains.

Another streak of dust follows a radial path out of Becquerel
crater; it likely traces out a gentle topographic depression,
beyond the eroded rim of the neighbouring old crater.

Meanwhile, dark sediments inside the small crater towards the far
left of the main image appear to have been blown out in a similar
direction by the powerful prevailing wind.

[Image]
Becquerel crater in 3D

These blowing sands continue to change the martian landscape even
today, exposing ancient rock formations in some locations, while
eradicating or covering younger features in others. Detailed
studies of these wind-blown patterns can often yield interesting
insights into the history of the Red Planet.
Received on Thu 05 Sep 2013 02:59:00 PM PDT