Hieroglyphic-like Features Point to Past Subsurface Water on Mars

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Although these strange features on Mars look a bit like hieroglyphics or geoglyphs such as the mysterious Nazca lines on Earth, they are completely natural features, ones that are found on Earth too.

This is one of the latest images from the

HiRISE camera on the Mars Reconnaissance Orbite

r.

Called 'rootless cones,' they form on lava flows that interact with subsurface water or ice. Their formation comes from an explosive interaction of lava with ground ice or water contained within the regolith beneath the flow. Vaporization of the water or ice when the hot lava comes in contact causes an explosive expansion of the water vapor, causing the lava to shoot upward, creating a rootless cone.

Dr. Alfred McEwen, HiRISE Principal Investigator, described the ancient lava flow as 'inflated.' "Lava inflation is a process where liquid is injected beneath the solid (thickening) crust and raises the whole surface, often raising it higher than the topography that controlled the initial lava emplacement," he wrote on the HiRISE website.

The scene above is located in Amazonis Planitia on Mars, a vast region covered by flood lava. McEwen said if this image were in color, we'e see the surface is coated by a thin layer of reddish dust, which avalanches down steep slopes to make dark streaks.

Similar features are found in Iceland, where flowing lava encountered water-saturated substrates.

[caption id="attachment_100193" align="aligncenter" width="250"]

Rootless cones (a) on Mars and (b) in Iceland. The scale of the Martian and terrestrial cones are comparable. Credit: University of Hawaii/Mars Orbiter Camera/MSSS.[/caption]

Just how big are these strange features on Mars and how old are they? "The cones are on the order of a hundred meters across and ten meters high," Colin Dundas from the US Geological Survey told Universe Today. "The age of these specific cones isn't known. They are on a mid- to late-Amazonian geologic unit, which means that they are young by Martian standards but could be as much as a few hundred million to over a billion years old."

If subsurface water or ice was part of their formation, could it still be there, underground?

"The water or ice that led to the formation of these cones was likely within a few meters (or less) of the surface, and so it's probably not there anymore," Dundas said. "At this low latitude (22 degrees north), shallow ground ice is currently unstable, and should sublimate on timescales much less than the likely age of the cones."

Dundas added that since ice stability varies as the obliquity changes, it's even possible that ice has come and gone repeatedly since the lava erupted.

See more views of this region on Mars on the

HiRISE website

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com