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Explanation: What created this unusual hole in Mars? The hole was discovered by chance on images of the dusty slopes of Mars' Pavonis Mons volcano taken by the HiRISE instrument aboard the robotic Mars Reconnaissance Orbiter currently circling Mars. The hole appears to be an opening to an underground cavern, partly illuminated on the image right. Analysis of this and follow-up images revealed the opening to be about 35 meters across, while the interior shadow angle indicates that the underlying cavern is roughly 20 meters deep. Why there is a circular crater surrounding this hole remains a topic of speculation,...

LOS ANGELES (AP) - The twin Mars rovers, one suffering from a balky wheel, have found a wonderland of weird rocks and enticing dunes along with more evidence that the Red Planet once had water, NASA scientists said Wednesday. The robotic vehicles landed in January and first found signs in March that Mars had water eons ago. The Spirit rover has now rolled nearly two miles across the plains of its Gusev Crater landing site and into an area dubbed the Columbia Hills. Perched about 30 feet above a plain, it recently found indications that water had altered an outcropping...

Sleepy Hollow," a shallow depression in the Mars ground near NASA's Spirit rover, may become an early destination when the rover drives off its lander platform in a week or so. That possible crater and other features delighted engineers and scientists examining pictures from the Mars Exploration Rover Spirit's first look around. Press Releases January 5, 2004 Mars Team Energized About "Sleepy Hollow" Near Rover "Sleepy Hollow," a shallow depression in the Mars ground near NASA's Spirit rover, may become an early destination when the rover drives off its lander platform in a week or so. That possible crater and...

A Mars-orbiting satellite recently spotted seven dark spots near the planet's equator that scientists think could be entrances to underground caves. The football-field sized holes were observed by Mars Odyssey's Thermal Emission Imaging System (THEMIS) and have been dubbed the seven sisters --Dena, Chloe, Wendy, Annie, Abbey, Nikki and Jeanne--after loved ones of the researchers who found them. The potential caves were spotted near a massive Martian volcano, Arisa Mons. Their openings range from about 330 to 820 feet (100 to 250 meters) wide, and one of them, Dena, is thought to extend nearly 430 feet (130 meters) beneath the...

Aug. 30, 2011 -- On the slopes of the vast Martian shield volcano Pavonis Mons, a rather odd-looking crater resides. Originally spotted by NASA's Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) earlier this year, mission managers decided to zoom in on the suspect feature using the awesome power of the MRO's High Resolution Imaging Science Experiment (HiRISE) camera. Indeed, as HiRISE has confirmed, this is one very odd-looking crater. From a distance, the crater appeared to have a black spot in its center, looking almost like the bulls eye on a dartboard. But on closer scrutiny the spot turned out...

A group of seventh-graders in California has discovered a mysterious cave on Mars as part of a research project to study images taken by a NASA spacecraft orbiting the red planet. The 16 students from teacher Dennis Mitchell's 7th-grade science class at Evergreen Middle School in Cottonwood, Calif., found what looks to be a Martian skylight — a hole in the roof of a cave on Mars.

WASHINGTON (Reuters) - An orbiting spacecraft has found evidence of what look like seven caves on the slopes of a Martian volcano, the space agency NASA said on Friday. The Mars Odyssey spacecraft has sent back images of very dark, nearly circular features that appear to be openings to underground spaces. "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 Northern Arizona University. "Their thermal behavior is not as steady as large caves on Earth that often maintain a fairly constant temperature, but it...

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 100 to 250 meters (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....

A very dark spot on Mars could be an entrance to a deep hole or cavern, according to scientists studying imagery taken by NASA's Mars Reconnaissance Orbiter. The geological oddity measures some 330 feet (100 meters) across and is located on an otherwise bright dusty lava plain to the northeast of Arsia Mons, one of the four giant Tharsis volcanoes on the red planet. The hole might be the sort of place that could support life or serve as a habitat for future astronauts, researchers speculated. Must be deep The Mars Reconnaissance Orbiter (MRO) used its High Resolution Imaging Science...

Today's set of image releases from the Mars Reconnaissance Orbiter HiRISE team included this one, of a fairly bland-looking lava plain to the northeast of Arsia Mons. Bland, that is, except for a black spot in the center. What's that black spot? It's a window onto an underground world.....

Nasa release on the topography of the south polar region of Mars Scientists studying pictures from Nasa's Odyssey spacecraft have spotted what they think may be seven caves on the surface of Mars.The candidate caves are on the flanks of the Arsia Mons volcano and are of sufficient depth their floors mostly cannot be seen through the opening. Details were presented here at the Lunar and Planetary Science Conference in Houston, Texas. Temperature data from Mars Odyssey's Themis instrument support the idea. The authors say that the possible discovery of caves on the Red Planet is significant. The caves...

Scientists studying pictures from Nasa's Odyssey spacecraft have spotted what they think may be seven caves on the surface of Mars. The candidate caves are on the flanks of the Arsia Mons volcano and are of sufficient depth their floors mostly cannot be seen through the opening. Details were presented here at the Lunar and Planetary Science Conference in Houston, Texas. Temperature data from Mars Odyssey's Themis instrument support the idea. The authors say that the possible discovery of caves on the Red Planet is significant. The caves may be the only natural structures capable of protecting primitive life forms...