NASA Reveals Bizarre Picture of Mysterious Hole on Slopes of Massive Martian Volcano

NASA has posted an image of an unusual hole on the slopes of a giant Martian volcano known as Pavonis Mons.

In the photo,which was snapped in 2011 by the space agency's Mars Reconnaissance Orbiter (MRO), a circular crater can be seen with very steep walls. At the center of this crater is an opening measuring around 115 feet across, which is the entrance to an underground cavern.

Much of the material that once filled the crater has sunk through the hole forming a pile of debris inside the cavern, according to the University of Arizona's Lunar & Planetary Laboratory (LPL.)

Using a digital model of the terrain around the hole, researchers have estimated that this debris pile is at least 203 feet tall. Furthermore, the top of the pile lies about 92 feet below the rim of the central opening, indicating that the underground cavity was once 295 feet deep, before the material from the crater fell inside.

Pavonis Mons hole, Mars
An image of the hole on the slopes of Pavonis Mons captured by the Mars Reconnaissance Orbiter. NASA, JPL, U. Arizona

This is intriguing from a geological perspective because it means the void is larger than most caves on Earth, according to the LPL. The caves on our planet that are larger than the Martian void were all formed through the process of water dissolving underground limestone. This process is unlikely to occur on Mars because these substances are not found in anywhere near the same quantities as they are on Earth.

Researchers think that on Mars, caverns like this could be the result of ancient volcanic activity. Pavonis Mons, which stands higher than Everest at 46,000 feet tall, is a shield volcano, which was formed by successive lava flows cooling and stacking on top of each other.

When hot lava flowed on the surface after eruptions, it would have cooled and hardened. In some cases, this may have insulated the lava below, allowing it to continue flowing. When this underground lava drained away, it may have left behind so-called "lava tube" caves.

These lava tubes are found on Earth in volcanic hotspots such as Hawaii, Iceland, and the Galapagos Islands. There are several potential candidates of lava tubes on both the moon and Mars.

Research presented by a team of scientists at the European Planetary Science Congress 2017 suggested these potential lava tube caves could have an important role to play in future space missions.

The team, led by Riccardo Pozzobon from the University of Padova, Italy, carried out the first comparison of lava tube caves on Earth and candidate lava tube caves on the moon and Mars. They found these caverns could potentially house human space settlements or even be promising places to search for signs of life, on Mars at least.

"The comparison of terrestrial, lunar and Martian examples shows that, as you might expect, gravity has a big effect on the size of lava tubes," Pozzobon said in a press release at the time. "On Earth, they can be up to 30 meters [98 feet] across. In the lower gravity environment of Mars, we see evidence for lava tubes that are 250 meters [820 feet] in width. On the Moon, these tunnels could be a kilometer [0.6 miles] or more across and many hundreds of kilometers in length."

He continued: "These results have important implications for habitability and human exploration of the moon but also for the search for extra-terrestrial life on Mars.

"Lava tubes are environments shielded from cosmic radiation and protected from micrometeorites, potentially providing safe habitats for future human missions. They are also, potentially, large enough for quite significant human settlements."