[meteorite-list] At the Foot of the Red Planet's Giant Volcano (Mars Express)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 8 Jul 2013 15:18:54 -0700 (PDT)
Message-ID: <201307082218.r68MIssr023488_at_zagami.jpl.nasa.gov>

http://www.esa.int/Our_Activities/Space_Science/Mars_Express/At_the_foot_of_the_Red_Planet_s_giant_volcano
    
At the foot of the Red Planet's giant volcano
European Space Agency
4 July 2013

[Image]
Hundreds of individual lava flows are seen frozen in time on the
flanks of Olympus Mons, the largest volcano in the Solar System.

The images, taken on 21 January 2013 by ESA's Mars Express, focus
on the southeast segment of the giant volcano, which towers some
22 km above the surrounding plains. This is more than double the
height of Mauna Kea, the tallest volcano on Earth at 10 km, when
measured from its oceanic base to summit.

[Image]
Olympus Mons in context

Like Mauna Kea, Olympus Mons is a shield volcano, with gently
sloping sides that extend outwards at low angles. But unlike other
shield volcanoes, it has an abrupt cliff edge, or scarp,
separating it from the surrounding plains.

The scarp circles the entire volcano, in places reaching 9 km
high. It was likely formed during a number of catastrophic
landslides on the flanks of the volcano, during which the
resulting debris was transported several hundred kilometres
beyond the extent of these images.

Lava flows cover the base of the volcano, punctuated by a handful
of pointy and flat-topped blocks that were either rotated or
uplifted during the collapse.

[Image]
Olympus Mons flank topography

The transition from the towering heights of the volcano down onto
the flat lava plain at the base of the scarp can be easily seen in
the colour-coded topography image.

In the leading colour image and perspective views, extensive
networks of narrow, overlapping lava flows are proof of an
extremely active volcanic past. The lava, long since solidified,
once spilled down the natural contours of the volcano, spreading
out into broad fans as it reached the scarp and plains below.

Flows that ended before reaching the scarp did so with rounded
tongues, as the lava cooled and crept to a stop.

[Image]
Perspective view of Olympus Mons flanks

Some lava flows are bounded by steep channel walls, while others
were contained in lava tubes. Zooming in to the top left portion
of the flank in the leading image reveals one example of an
ancient lava tube, its winding track partially exposed in channel
segments where the roof of the tunnel has since collapsed.

[Image]
Perspective view of Olympus Mons flanks

The chaotic lava flows on the flanks provide a stark contrast to
the smooth plains seen surrounding the volcano.

Here, only two prominent features are visible: a "wrinkle ridge"
in the lower centre of the main image, which formed as lava cooled
and contracted to buckle up and distort the surface, and a channel
system that branches out into a horseshoe shape. This channel was
likely carved by lava, but water may have once flowed here, too.

[Image]
The flank of Olympus Mons in 3D

The occurrence of only a few small impact craters in this scene
shows that it is relatively young compared with more heavily
cratered regions elsewhere on Mars - the older the surface, the
greater the exposure time to impact events by asteroids or comets.

Furthermore, by looking at how the lava flows overlap, one can
determine their relative ages: those that lie on top, cutting
through and overprinting other flows, are the youngest.

For example, the vast lava plain surrounding the volcano truncates
the majority of lava flows extending from the flanks, suggesting
it is younger still, and that it originated from a location
outside of this scene.

The volcanic region hosting Olympus Mons and several other large
volcanoes is thought to have been active until tens of millions of
years ago, relatively recent on the planet's geological timescale
that spans 4.6 billion years.
Received on Mon 08 Jul 2013 06:18:54 PM PDT