Giant volcano on Mars hiding in plain sight

• Scientists discovered a giant Martian volcano hiding in plain sight near the planet’s equator.
• The heavily eroded volcano provides insight into Mars’ evolution over time.
• Conditions for life may exist there, as possible glacial remains lie at the volcano’s base, creating a potential destination for future scientific exploration.

SETI published this original article on March 13, 2024. Edits by EarthSky.

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Giant volcano on Mars hiding in plain sight

At the 55th Lunar and Planetary Science Conference held in The Woodlands, Texas, scientists revealed the discovery of a giant volcano and a possible sheet of buried glacial ice. The discovery is from the eastern part of Mars’ Tharsis volcanic province, near the planet’s equator. Mars-orbiting spacecraft have imaged this region repeatedly since Mariner 9 in 1971. But the region is deeply eroded beyond easy recognition, so the giant volcano had been hiding in plain sight for decades.

The newly found volcano lies in one of Mars’ most iconic regions. It’s at the boundary between the heavily fractured maze-like Noctis Labyrinthus (Labyrinth of the Night) and the monumental canyons of Valles Marineris (Valleys of Mariner).

Giant volcano on Mars named Noctis volcano

Temporarily designated Noctis volcano pending an official name, the structure’s center is at 7° 35′ S, 93° 55′ W. It reaches 9,022 meters (29,600 feet) in elevation and spans 450 kilometers (280 miles) in width. The volcano’s gigantic size and complex modification history indicate it’s been active for a very long time. Its southeastern sections have a thin, recent volcanic deposit beneath which glacial ice is likely still present. This combined giant volcano and possible glacial ice discovery is significant. It points to an exciting new location to study Mars’ geologic evolution through time, search for life and explore with robots and humans in the future.

Discovery of the giant volcano on Mars

Pascal Lee, a planetary scientist with the SETI Institute and the Mars Institute based at NASA Ames Research Center, was the lead author of the study. Lee said:

We were examining the geology of an area where we had found the remains of a glacier last year when we realized we were inside a huge and deeply eroded volcano.

Several clues give away the volcanic nature of the jumbled, layered mesas and canyons in this part of Noctis Labyrinthus. The central summit area has several elevated mesas forming an arc. These areas reach a regional high and slope downhill away from the summit area. The gentle outer slopes extend out to 225 kilometers (140 miles) away in different directions. A caldera remnant – the remains of a collapsed volcanic crater – is near the center of the structure. Lava flows, pyroclastic deposits (made of volcanic particulate materials such as ash, cinders, pumice and tephra) and hydrated mineral deposits occur in several areas within the structure’s perimeter.

A smoking gun

Sourabh Shubham, a graduate student at the University of Maryland’s Department of Geology and the study’s co-author, explained:

This area of Mars is known to have a wide variety of hydrated minerals spanning a long stretch of Martian history. A volcanic setting for these minerals had long been suspected. So, it may not be too surprising to find a volcano here. In some sense, this large volcano is a long-sought ‘smoking gun’.

The study also reports the discovery of a large, 5,000-square-kilometer (1,930-sq-mi) area of volcanic deposits. The deposits within the volcano’s perimeter consist of many low, rounded and elongated, blister-like mounds. Scientists interpret this “blistered terrain” as a field of “rootless cones,” mounds produced by explosive steam venting or swelling. This venting happens when a thin blanket of hot volcanic materials comes to rest on top of a water or ice-rich surface.

Remains of a glacier

Just a year ago, Lee, Shubham and their colleague John W. Schutt had identified the spectacular remains of a glacier. They did so through a sizeable erosional opening in the same volcanic blanket. The researchers saw a light-toned deposit of sulfate salt with the morphologic traits of a glacier. They interpreted the sulfate deposit – made mainly of jarosite (a hydrous sulfate) – formed when the blanket of volcanic pyroclastic materials came to rest on a glacier and reacted chemically with the ice. Breached rootless cones identified in the current study show similar occurrences of polyhydrated sulfates. This further suggests the blistered volcanic blanket may be hiding a vast sheet of glacial ice underneath it.

The history of the volcano

The Noctis volcano presents a long and complex history of modification. That history may be from a combination of fracturing, thermal erosion and glacial erosion. Researchers believe the volcano is a vast shield of layered accumulations of pyroclastic materials, lavas and ice. The ice resulted from repeated buildups of snow and glaciers on its flanks through time. As fractures and faults eventually developed – in particular in connection with the uplift of the broader Tharsis region on which the volcano sits – lavas began to rise. The lava rose through different parts of the volcano, leading to thermal erosion and the removal of vast amounts of buried ice. Eventually, it led to the catastrophic collapse of entire sections of the volcano.

Subsequent glaciations continued their erosion, giving many canyons within the structure their present distinctive shape. In this context, the “relict glacier” and the possible buried sheet of glacial ice around it might be remnants of the latest glaciation episode affecting the Noctis volcano.

Mysteries remain

But much about the newly discovered giant volcano remains a mystery. Although it’s clear it’s been active for a long time and began to build up early in Mars’ history, it’s unknown how early. Similarly, although it experienced eruptions in modern times, it’s unknown if it’s still volcanically active and might erupt again. And if it’s been active for a long time, could the combination of sustained warmth and water from ice have allowed the site to harbor life?

The site is already emerging as an exciting new location to study Mars’ geologic evolution, search for life and plan future robotic and human exploration. The possible presence of glacial ice at shallow depths near the equator means humans could potentially explore a less frigid part of the planet while still being able to extract water for hydration and manufacturing rocket fuel.

Reasons to be excited

Lee said:

It’s really a combination of things that makes the Noctis volcano site exceptionally exciting. It’s an ancient and long-lived volcano so deeply eroded that you could hike, drive or fly through it to examine, sample and date different parts of its interior to study Mars’ evolution through time. It has also had a long history of heat interacting with water and ice, which makes it a prime location for astrobiology and our search for signs of life. Finally, with glacial ice likely still preserved near the surface in a relatively warm equatorial region on Mars, the place is looking very attractive for robotic and human exploration.

Bottom line: A giant volcano on Mars has been hiding in plain sight. It has experienced eruptions in “modern times” and could erupt again. It’s also the site of glacial ice, which has implications for finding life on Mars or for human exploration of the planet.

Via SETI

Read more: More evidence Mars is still volcanically alive