Giant cave found on Mars

A beautifully conical crater pit divots the flank of ancient volcano Pavonis Mons on Mars. This digital terrain model is color coded for elevation with red for higher terrain and blue lower. Click to enlarge. Credit: NASA/JPL/University of Arizona

Caves are nothing new to the Red Planet, but a recent photo taken by NASA’s Mars Reconnaissance Orbiter (MRO) reveals a particularly large example on the flanks of the shield volcano Pavonis Mons.

Highest resolution image of the crater pit cropped and enhanced so you can see the opening at the bottom and a hint of the debris pile. Credit: NASA/JPL/University of Arizona

The walls of the pit are very steep –  if they were any steeper, debris would crumble off the walls and roll down through the hole at the crater’s base. Material that once filled the pit drained down the walls to form a pile of debris in a subterranean chamber below. The top of this debris pile can be seen through the opening about 92 feet (28 meters) farther down, although only a hint of it appears in these photographs.

An approximate cross-section of the pit showing the tall pile of rock and soil on the floor of a possible lava tube cavern hidden beneath the extinct volcano Pavonis Mons. Credit: Bob King

Based on a digital model of the ancient volcano’s terrain, scientists can estimate how much material was once in the pit and how big the pile below must be. The results are amazing – a huge hill of soil and rocks some 203 feet (62 meters) tall stands below the opening in the crater’s floor. Given that the top of this pile is 92 feet below the rim of the central hole, this tells us that the empty cavity was once 295 feet deep (90 meters) deep, prior to collapse and infilling.

Natural light view of the crater pit and its central opening to a cavern below. Credit: NASA/JPL/University of Arizona

Only a few caves on Earth are this deep. Most of those are created when water dissolves limestone. Limestone remains elusive on Mars, so planetary astronomers look to lava tubes as the most likely source of the subterranean cavern beneath the pit.

A skylight over a lava tube still coursing with lava on Kilauea in Hawaii. Credit: Martin Ruzek, USGS Hawaiian Volcano Observatory

Most Martian volcanoes are built up from multiple lava flows pouring down their flanks eruption after eruption. Sometimes the surface lavas cool and solidify to form a roof over lavas that continue to flow in underground lava tubes.

As the tubes drain, they can leave empty caverns – caves as it were. Sections of the roof can later collapse forming openings into an underground network of skylights.

Perhaps that’s what were seeing here – a window into the past when lava coursed across the thickening slopes of Pavonis Mons. One wonders whether geothermal springs might still bubble and trickle within the cave’s recesses. Could thermophilic (heat-loving) bacteria have evolved on Mars as they did on Earth and gained a foothold there? And might their descendants still be holed up as the rest of the planet became a desert sterilized by ultraviolet light from the sun?  In my crystal ball I see future mini-drone missions to Martian caves followed by visits from astronauts.

Maybe someday we’ll see what’s up down that hole.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

10 thoughts on “Giant cave found on Mars

  1. Hey Bob, that picture from Hawaii is amazing. That’s a natural color image–not enhanced? Wow. But shouldn’t there be some smoke or fumes or indication of heat? Keep up the good work. –Norman

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