Mysterious Mars rock formation has explosive explanation

The bizarre Medusae Fossae landscape likely traces back to volcanic eruptions.

Amanda Kooser
Freelance writer Amanda C. Kooser covers gadgets and tech news with a twist for CNET. When not wallowing in weird gear and iPad apps for cats, she can be found tinkering with her 1956 DeSoto.
Amanda Kooser
2 min read

NASA's Mars Reconnaissance Orbiter captured this infrared-color image of a section of Medusae Fossae.

NASA/JPL-Caltech/Univ. of Arizona

The Medusae Fossae Formation rises near the equator of Mars. The soft rock has been carved by wind erosion into a collection of ridges, valleys and striking mesas. It's massive. It's strange. And scientists are now tracing its origin to explosive volcanic activity in Mars' deep past.

NASA has referred to Medusae Fossae as "an enigmatic pile of eroding sediments." UFO enthusiasts once spotted what they believed to be a UFO there, which is mainly a testament to the exotic shapes formed in the wind-blasted area. 


A wind-eroded hill in Medusae Fossae.

High Resolution Stereo Camera/European Space Agency.

Researchers have suggested several possible explanations for the sedimentary formation, including the presence of ice-rich deposits or volcanic deposits. 

A study published in the Journal of Geophysical Research: Planets now traces Medusae Fossae to violent volcanic eruptions dating to over 3 billion years ago.

The researchers from Johns Hopkins University in Baltimore used data from Mars-orbiting spacecraft to measure the density of Medusae Fossae. They determined the porous formation must have developed from explosive volcanic deposits and not icy deposits. 

"The eruptions that created the deposit could have spewed massive amounts of climate-altering gases into Mars's atmosphere and ejected enough water to cover Mars in a global ocean," suggests study co-author Lujendra Ojha in a release Monday from the American Geophysical Union.

The study's authors say Medusae Fossae is "the largest known pyroclastic deposit in the solar system." Wind erosion has taken a toll over the many years, with up to half of the original rock now eroded away, leaving us with the scenic ridges and valleys now visible from orbit. 

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