The Northern Arizona University (NAU) press release is reproduced below:

Applying techniques used to scope out caves on Earth to probe the possibility of caves on Mars is paying off.

NAU researchers Glen Cushing and Jut Wynne, working at the U.S. Geological Survey, propose that photos from the Mars Odyssey mission reveal football-field size holes that could be entrances to caves.

"If there is life on Mars, there is a good chance you'd find it in caves," said Wynne, an NAU graduate student in biological sciences and project leader for the USGS Earth-Mars Cave Detection Program.

Researchers propose these images of seven black spots near a massive Martian volcano may actually be caves rather than impact craters. The images were taken from the Thermal Emission Imaging System aboard NASA's Mars Odyssey orbiter.

He said the possible discovery could lead to more focused Mars explorations.

Martian caves are considered the "best potential havens for life" because they would be protected from surface radiation and other factors, he said.

"The Martian surface is an extremely harsh environment, so the significance of caves is in their protective nature," said Cushing, a graduate teaching assistant in NAU's Department of Physics and Astronomy, who was the first to spot the black areas on the photographs. "Caves on Mars could become habitats for future explorers, or could be the only structures that preserve evidence of past or present microbial life."

Cushing and Wynne, along with Tim Titus, an astrophysicist with USGS, and Phil Christensen, the chief scientist for the NASA imaging instrument and a researcher from Arizona State University, recently submitted their findings in a research paper at the 38th Lunar and Planetary Science Conference.

"We're suggesting that the seven black spots are skylights to areas where the surface may have collapsed into a chamber below," Wynne said. "Preserved evidence of past life on Mars might only be found in caves, and such discovery would be of unparalleled significance."

The claim for caves is based on an analysis of photographs from the Thermal Emission Imaging System aboard NASA's Mars Odyssey orbiter, which revealed seven black spots near a massive Martian volcano, Arsia Mons. Although this area of Mars is known for geological occurrences, the researchers said the dark spots do not look like impact craters because they don't have raised rims or blast patterns.

"This is a very interesting discovery with positive implications," said Nadine Barlow, an associate professor in physics and astronomy at NAU and expert on Martian impact craters. "Caves on Mars could be good places for long-term ice accumulation and that would make them ideal locations to look for life on Mars as well as valuable reservoirs for water to support future human exploration of the planet."

The Earth-Mars Cave Detection Program's overall objective is to develop techniques for systemically detecting caves on Earth in the thermal infrared and then applying these techniques to searching for caves on Mars, Wynne explained.

The team reported possible caverns ranging from 330 to 825 feet wide and 425 feet deep They've been named after loved ones of the researchers: Dena, Chloe, Wendy, Annie, Abbey, Nikki and Jeanne.

Christensen said the first avenue for further observations could be provided by NASA's latest Red Planet probe, the Mars Reconnaissance Orbiter.

"The spacecraft's high-resolution camera could take a closer look at the seven sisters—including sidelong glances that might show whether the features open up into wider chambers beneath," Christensen said.

Source: NAU News Release

The press release is reproduced below:

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown@nasa.gov

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278
guy.webster@jpl.nasa.gov

RELEASE: 07-207

NASA Orbiter Finds Possible Cave Skylights on Mars
PASADENA, Calif. -- NASA's Mars Odyssey spacecraft has discovered entrances to seven possible caves on the slopes of a Martian volcano. The find is fueling interest in potential underground habitats and sparking searches for caverns elsewhere on the Red Planet.

Very dark, nearly circular features ranging in diameter from about 328 to 820 feet puzzled researchers who found them in images taken by NASA's Mars Odyssey and Mars Global Surveyor orbiters. Using Mars Odyssey's infrared camera to check the daytime and nighttime temperatures of the circles, scientists concluded that they could be windows into underground spaces.

Evidence that the holes may be openings to cavernous spaces comes from the temperature differences detected from infrared images taken in the afternoon and in the pre-dawn morning. From day to night, temperatures of the holes change only about one-third as much as the change in temperature of surrounding ground surface.

"They are cooler than the surrounding surface in the day and warmer at night," said Glen Cushing of the U.S. Geological Survey's Astrogeology Team and of Northern Arizona University, Flagstaff, Ariz. "Their thermal behavior is not as steady as large caves on Earth that often maintain a fairly constant temperature, but it is consistent with these being deep holes in the ground."

A report of the discovery of the possible cave skylights by Cushing and his co-authors was published online recently by the journal Geophysical Research Letters.

"Whether these are just deep vertical shafts or openings into spacious caverns, they are entries to the subsurface of Mars," said co-author Tim Titus of the U.S. Geological Survey in Flagstaff. "Somewhere on Mars, caves might provide a protected niche for past or current life, or shelter for humans in the future."

The discovered holes, dubbed "Seven Sisters," are at some of the highest altitudes on the planet, on a volcano named Arsia Mons near Mars' tallest mountain.

"These are at such extreme altitude, they are poor candidates either for use as human habitation or for having microbial life," Cushing said. "Even if life has ever existed on Mars, it may not have migrated to this height."

The new report proposes that the deep holes on Arsia Mons probably formed as underground stresses around the volcano caused spreading and faults that opened spaces beneath the surface. Some of the holes are in line with strings of bowl-shaped pits where surface material has apparently collapsed to fill the gap created by a linear fault.

The observations have prompted researchers using Mars Odyssey and NASA's newer Mars Reconnaissance Orbiter to examine the Seven Sisters. The goal is to find other openings to underground spaces at lower elevations that are more accessible to future missions to Mars.

"The key to finding these was looking for temperature anomalies at night -- warm spots," said Phil Christensen of Arizona State University, Tempe, principal investigator for the Thermal Emission Imaging System on Mars Odyssey. That instrument produced both visible-light and infrared images researchers used for examining the possible caves.

"No other instrument at Mars could give the thermal information crucial to this research," said the project scientist for Mars Odyssey, Jeffrey Plaut of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This is a great example of the exciting discoveries Odyssey continues to make." Mars Odyssey reached Mars in 2001, years before any of the other spacecraft currently examining the planet. Its predecessor, Mars Global Surveyor, ended its mission last year.

The Jet Propulsion Laboratory manages Mars Odyssey and Mars Reconnaissance Orbiter for the NASA Science Mission Directorate, Washington. Arizona State University operates the Mars Odyssey's Thermal Emission Imaging System. For additional information about Mars Odyssey and the new findings, visit:


Source: NASA Press Release 07-207

Seven Possible Cave Skylights on Mars



Seven very dark holes on the north slope of a Martian volcano have been proposed as possible cave skylights, based on day-night temperature patterns suggesting they are openings to subsurface spaces. These six excerpts of images taken in visible-wavelength light by the Thermal Emission Imaging System camera on NASA's Mars Odyssey orbiter show the seven openings. Solar illumination comes from the left in each frame. The volcano is Arsia Mons, at 9 degrees south latitude, 239 degrees east longitude.

The features have been given informal names to aid comparative discussion. They range in diameter from about 100 meters (328 feet) to about 225 meters (738 feet). The candidate cave skylights are (A) "Dena," (B) "Chloe," (C ) "Wendy," (D) "Annie," (E) "Abby" (left) and "Nikki," and (F) "Jeanne." Arrows signify north and the direction of illumination.

Mars Odyssey is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The orbiter's Thermal Emission Imaging System was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing, Santa Barbara, Calif., and is operated by Arizona State University.

Image credit: NASA/JPL-Caltech/ASU/USGS

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+ Full resolution (without labels) 359Kb

Source: NASA - Missions - Odyssey

Temperature Behavior of Possible Cave Skylight on Mars



Each of the three images in this set covers the same patch of Martian ground, centered on a possible cave skylight informally called "Annie," which has a diameter about double the length of a football field. The Thermal Emission Imaging System camera on NASA's Mars Odyssey orbiter took all three, gathering information that the hole is cooler than surrounding surface in the afternoon and warmer than the surrounding surface at night. This is thermal behavior that would be expected from an opening into an underground space.

The left image was taken in visible-wavelength light. The other two were taken in thermal infrared wavelengths, indicating the relative temperatures of features in the image. The center image is from mid-afternoon. The hole is warmer than the shadows of nearby pits to the north and south, while cooler than sunlit surfaces. The thermal image at right was taken in the pre-dawn morning, about 4 a.m. local time. At that hour, the hole is warmer than all nearby surfaces.

Annie and six other features with similar thermal behavior are on the northern slope of a high Martian volcano named Arsia Mons, which is at 9 degrees south latitude, 239 degrees east longitude.

Mars Odyssey is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The orbiter's Thermal Emission Imaging System was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing, Santa Barbara, Calif., and is operated by Arizona State University.

Image credit: NASA/JPL-Caltech/ASU/USGS

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Source: NASA - Missions - Odyssey

Very interesting, Waspie, thanks for sharing. From what I learnt in astronomy, Mars did not have any volcanic activity, that the core had cooled. So, this would kind of put that into question, wouldn't it? If there is heat coming out of these caves, then there would have to be some kind of activity still in there. Or am I wrong?

Mars had massive volcanic activity. The largest known volcano, Olympus Mons (3 times taller than Everest) is on Mars. However that volcanism seems to be long in the past.


If I understand the articles correctly it is not that these possible caves are giving off heat, it's that they have a different temperature to the surrounding surface. From the third post:

If the caves were giving off heat then you would expect them to be warmer than the surrounding surface day and night. The behaviour as seen suggests that they take longer to warm up than the surrounding area when the sun rises but take longer to cool down once the sun sets.

From the photographs they look quite symmetrical?

I agree, Evil, they are quite symmetrical. And it is quite interesting how they seem to retain the heat.

Some of them are reasonably symmetrical, but not unnaturally so, and to call the fourth one symmetrical is stretching the point a bit.



I googled "Skylight caves" and found lots of images of similar caves on Earth. They look remarkably similar to these Martian features. They are caused when the roof of a lava tube collapses. It souldn't really be surprising that they are fairly round, it you have ever seen a road collapse over an underground pipe that tends to leave a roundish hole too. It's the same principle on a larger scale.


Again this is nothing unexpected. During the day the sun will be shinning on the surrounding land, warming it up, whilst the cave is still in shadow. The surrounding land will be warmer than the cave. When the sun sets the ground quickly radiates it's heat away. The air in the cave, however, is trapped. There is only the entrance hole for the warmer air to escape from hence the cave will appear warmer than the surrounding land at night.

September 21, 2007: NASA's Mars Odyssey spacecraft has discovered entrances to seven possible caves on the slopes of a Martian volcano. The find is fueling interest in potential underground habitats and sparking searches for caverns elsewhere on the Red Planet.

Very dark, nearly circular features ranging in diameter from about 328 to 820 feet puzzled researchers who found them in images taken by NASA's Mars Odyssey and Mars Global Surveyor orbiters. Using Mars Odyssey's infrared camera to check the daytime and nighttime temperatures of the circles, scientists concluded that they could be windows into underground spaces.

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The Arizona State University (ASU) press release is reproduced below:

A heat-sensitive camera designed at Arizona State University and flying on NASA's Mars Odyssey orbiter has led a team of Mars geologists to find seven small, deep holes on the flanks of Arsia Mons, a giant volcano on Mars. The holes may be openings, called skylights, in the ceilings of underground caves. The discovery is announced in a scientific paper published recently in Geophysical Research Letters.

The team of scientists includes Philip Christensen of ASU, plus Glen Cushing and Tim Titus of the U.S. Geological Survey in Flagstaff, and Judson Wynne of Northern Arizona University. Cushing is the lead author on the paper.

Christensen, a Regents Professor of geological science in ASU's School of Earth and Space Exploration, designed the Thermal Emission Imaging System (THEMIS), the instrument the team used to make the discovery. THEMIS has been photographing the Red Planet at five visual and 10 infrared wavelengths since February 2002.

Says Christensen, "THEMIS is the only heat-sensing imager currently orbiting Mars." Temperature data was the key in spotting the potential cave skylights, he notes.

The features the team found are dark, nearly circular holes in the ground with diameters ranging from 100 to 250 meters (yards). The holes appear in images of Arsia Mons taken by Mars Odyssey and Mars Global Surveyor orbiters. Located in the volcanic region of Tharsis, Arsia is one of the larger volcanoes on Mars, and like the rest of Tharsis, it has a heavy coating of dust.

"We examined the flanks of the volcano in nighttime infrared images, looking for temperature anomalies – warm spots," explains Christensen. "Then when we re-examined the locations in daytime images, we saw the small, deep holes in the ground."

Dusty surfaces, he says, become hot during the day, both on Earth and Mars. But at night, dust and sand give up heat quickly, becoming very cold shortly before sunrise. The holes, however, changed temperature by only two-thirds as much as the surface.

Says Christensen, "We saw that we had dark holes that are warm at night, but cool by day. The best way to explain that is to have a deep hole with vertical walls, so you're looking at a rocky surface free from sand and dust."

The team suggests that the deep holes on Arsia Mons probably formed as faults created stresses that opened spaces underground. Some of the holes are in line with strings of bowl-shaped pits where the surface has collapsed.

The observations have been discussed at meetings with other Mars scientists earlier this year, and they have prompted researchers using Mars Odyssey and NASA's newer Mars Reconnaissance Orbiter to search for other openings to underground spaces.

Christensen adds, "The temperature data is what really separated these unique holes from millions of run-of-the-mill craters, volcanic vents, and collapse pits."
Robert Burnham, robert.burnham@asu.edu
(480) 458-8207
School of Earth and Space Exploration
College of Liberal Arts and Sciences

Source: ASU News Release