NASA Mars Odyssey THEMIS Image: Alba Patera Collapse Pits

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Context image credit: NASA/Mars Orbiter Laser Altimeter (MOLA) Team
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We will be looking at collapse pits for the next two weeks. Collapse

pits on Mars are formed in serveral ways. In volcanic areas, channelized

lava flows can form roofs which insulate the flowing lava. These features

are termed lava tubes on Earth and are common features in basaltic flows.

After the lava has drained, parts of the roof of the tube will collapse

under its own weight. These collapse pits will only be as deep as the

bottom of the original lava tube. Another type of collapse feature

associated with volcanic areas arises when very large eruptions completely

evacuate the magma chamber beneath the volcano. The weight of the volcano

will cause the entire ediface to subside into the void space below it.

Structural features including fractures and graben will form during the

subsidence. Many times collapse pits will form within the graben.

In addition to volcanic collapse pits, Mars has many collapse pits formed

when volatiles (such as subsurface ice) are released from the surface

layers. As the volatiles leave, the weight of the surrounding rock

causes collapse pits to form.

These collapse pits are found within graben surrounding Alba Patera.

Alba Patera is an old volcano that has subsided after it’s magma chamber

was evacuated.

[Source: ASU THEMIS Science Team]

NASA’s Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA’s Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

Image Credit: NASA/JPL/Arizona State University