Mars Express Images: Lava Tubes on Pavonis Mons

http://www.esa.int/SPECIALS/Mars_Exp...AD9ATME_0.html

Lava tubes on Pavonis Mons
Mars Express
European Space Agency
23 May 2006

These images, taken by the High Resolution Stereo Camera (HRSC) on
board
ESA's Mars Express, show Pavonis Mons, the central volcano of the three
'shield' volcanoes that comprise Tharsis Montes.


[Map showing Pavonis Mons in context]

ESA's Mars Express spacecraft obtained these images using the HRSC
during orbit 902 with a ground resolution of approximately 14.3 metres
per pixel. The images were acquired in the region of Pavonis Mons, at
approximately 0.6? South and 246.4? East.

The context map is centred on Pavonis Mons, one of the three volcanoes
called Tharsis Montes (the others being Arsia and Ascreus Montes,
aligned with Pavonis in a line nearly 1500 km long).


[Pavonis Mons in Tharsis Montes]

Pavonis Mons, rising roughly 12 km above the surrounding plains, is the
central volcano of the three 'shield' volcanoes that comprise Tharsis
Montes. Gently sloping shield volcanoes are shaped like a flattened
dome
and are built almost exclusively of lava flows.

The dramatic features visible in the colour image are located on the
south-west flank of Pavonis Mons. Researchers believe these are lava
tubes, channels originally formed by hot, flowing lava that forms a
crust as the surface cools. Lava continues to flow beneath this
hardened
surface, but when the lava production ends and the tunnels empty, the
surface collapses, forming elongated depressions. Similar tubes are
well
known on Earth and the Moon.


[Lava tubes on Pavonis Mons, in perspective]

The long, continuous lava tube in the northwest of the colour image
extends over 59 km and ranges from approximately 1.9 km to less than
280
m wide.

Pit chains, strings of circular depressions thought to form as the
result of collapse of the surface, are also visible within the colour
image. In the northeast, there is a clear distinction between the
brighter terrain at higher elevations and darker material located down
slope. In the southwest, the lava tubes appear to be covered by
subsequent lava flows.


[3D anaglyph of Pavonis Mons in Tharsis Montes]

By studying Martian volcanoes, scientists can obtain information
regarding this intriguing planet. For example, the gradual flank slopes
and the flattened, dome-like appearance of Pavonis Mons suggest that
low-viscosity lava formed this volcano.

The colour scene was derived from the three HRSC-colour channels and
the
nadir channel. The 3D anaglyph image was calculated from the nadir and
one stereo channel. Image resolution has been decreased for use on the
internet.

By studying Martian volcanoes, scientists can obtain information
regarding this intriguing planet. For example, the gradual flank slopes
and the flattened, dome-like appearance of Pavonis Mons suggest that
low-viscosity lava formed this volcano.


Low-viscosity lava may imply magma-phreatism, I think.

"z7-x332a" wrote in message
oups.com...
By studying Martian volcanoes, scientists can obtain information
regarding this intriguing planet. For example, the gradual flank slopes
and the flattened, dome-like appearance of Pavonis Mons suggest that
low-viscosity lava formed this volcano.


Low-viscosity lava may imply magma-phreatism, I think.

I think the existence of the lava tubes makes that obvious.

George