Images by the two probes show near-circular holes about 328 to 738 feet (100 to 225 meters) across. What is important in this discovery is the climate possible within the subterranean spaces. The range of temperatures inside the caves could be only one-third of the temperature range on the Martian surface. Such a desirable situation could harbor primitive life—either in the past or presently. In the future, such protective underground cavities could be places where astronauts live and work—away from the harsher conditions on the surface.

The original report on the seven caves was published in the journal Geophysical Research Letters under the title “THEMIS observes possible cave skylights on Mars”. Its authors are G.E. Cushing (Northern Arizona University, Flagstaff), T.N. Titus (U.S. Geological Survey), J.J. Wynne (Northern Arizona University), and P.R. Christensen (Arizona State University, Tempe).

The paper’s abstract states: “Seven possible skylight entrances into Martian caves were observed on and around the flanks of Arsia Mons by the Mars Odyssey Thermal Emission Imaging System (THEMIS). Distinct from impact craters, collapse pits or any other surface feature on Mars, these candidates appear to be deep dark holes at visible wavelengths while infrared observations show their thermal behaviors to be consistent with subsurface materials. Diameters range from 100 m to 225 m, and derived minimum depths range between 68 m and 130 m. Most candidates seem directly related to pit-craters, and may have formed in a similar manner with overhanging ceilings that remain intact.”

The Thermal Emission Imaging System (THEMIS) imaged the Martian caves while onboard the 2001 Mars Odyssey spacecraft. NASA’s robotic spacecraft lifted off on April 7, 2001 and arrived at Mars on October 24, 2001. (The name “2001 Mars Odyssey” is in reference to the movie “2001: A Space Odyssey”.) It began its scientific mapping of the planet on February 19, 2002—primarily searching for evidence of past or present water and volcanic activity on Mars, while also helping the Mars Exploration Rovers Spirit and Opportunity communicate with ground controllers on Earth.

For additional information on 2001 Mars Odyssey, go to http://mars.jpl.nasa.gov/odyssey/index.html.

The Mars Global Surveyor was launched in November 1996. Its mission was taken over by the 2001 Mars Odyssey spacecraft in 2001, but continued to operate until November 2006. NASA officially ended its mission in January 2007 after all contact with the probe was lost.

This article is based on the NASA article “NASA Orbiter Finds Possible Cave Skylights on Mars”.

{moscomment}