We have been looking out over a gigantic volcano on Mars for 50 years

A gigantic volcano bigger than Mount Everest has been discovered on Mars – but perhaps most amazingly, it was right there in the images collected by Mariner 9 in 1972. It is suspected that there is a layer of glacial ice underneath, and the likely combination of water and heat means that if there is life on Mars, this is one of the most likely places to find it.

When Mariner 9 reached Mars in November 1971, it marked the first time a spacecraft had successfully orbited another planet. Besides being a significant victory for America in the space race (two Russian vehicles were launched before that, but arrived afterwards), it revealed the planets’ gigantic volcanoes. However, it turns out there was another volcano in the footage that no one noticed, and we’ve been missing it ever since – until now.

Volcanoes on Mars are large but not numerous, making every new discovery important. The volcanic province of Tharsis consists of a gigantic bulge, the most prominent geographical feature on Mars, topped by three gigantic former volcanoes. Just west of Tharsis lies Olympus Mons, which rises 21.9 kilometers (14 miles) above the surrounding land and is the size of Poland, making it the largest single volcano ever found.

The new discovery, tentatively named ‘Noctis Volcano’, is located on the eastern side of Tharsis province. The summit is 9,028 meters (29,619 feet) above the surrounding sand, so it’s no match for Olympus Mons, but it’s still the seventh highest spot in the world. At 450 kilometers (280 miles) wide, it is three times wider than the island of Hawai’i.

Despite this, and at a location less than 8 degrees south of Mars’ equator, Noctis was not spotted because its collapsed shape does not resemble other volcanoes. Its discovery was indeed quite accidental.

Noctis Volcano with Noctis Labyrinthus to the west and the mighty Valles Marineris to the east

Noctis volcano with a labyrinth of the same name to the west and the mighty Valles Marineris to the east

Image credits: Background images: NASA Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) mosaic and Mars Global Surveyor (MGS) Mars Orbiter Laser Altimeter (MOLA) digital elevation model. Geological interpretation and annotations by Pascal Lee & Sourabh Shubham 2024).

“We were investigating 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,” said Dr. Pascal Lee of the SETI Institute in a statement. Lee and Sourabh Shubham, a graduate student at the University of Maryland, used images taken by seven orbiter missions, from Mariner 9 to those still active, to make and confirm the discovery.

Some of Mars’ shield volcanoes have a classic cone shape almost worthy of Mount Fuji, but Noctis is a jumble of plateaus and canyons surrounded by a gentle outer slope, which conceals its nature. At its center is a collapsed volcanic crater – and once Lee and Shubham looked closely, they could see lava flows and deposits of ash and pumice covering a combined area of ​​5,000 square kilometers (1,930 square miles).

“This area of ​​Mars is known to contain a wide variety of hydrated minerals spanning a long period of Martian history. A volcanic environment for these minerals has long been suspected,” Shubham said. “So it might not be surprising to find a volcano here. In a sense, this great volcano is a long-sought ‘smoking gun’.”

The glacier is covered by a sulfate deposit that formed when volcanic material reacted with the ice, prompting the couple to search for the source of the material. Lee and Shubham suspect that the glacier they found is just the edge of a huge sheet of ice, some of which is buried only 1 to 3 meters deep.

High-resolution imaging of the Noctis volcano compared to altimeters revealing the height of the parts above the Martian background

High-resolution imaging of Noctis volcano compared to altimetry revealing the height of its parts above the Martian background

Image credits: Left: Mars Express HRSC color mosaic © ESA/DLR/FU Berlin CC BY-SA 3.0 IGO; Right: Background image: same as Left; NASA MGS MOLA digital elevation model. Geological interpretation and annotations by Pascal Lee and Sourabh Shubham 2024).

Volcanoes on Mars are so large not only because they have less gravity to overcome, but also because they suffer nothing from the amount of erosion that similar structures on Earth would experience. However, Noctis has been exposed to more erosion than its counterparts, as the heat of rising lava and the cold of the ice interacted to cause fractures and catastrophic collapses.

Because it is so much more eroded than its counterparts, it is easily assumed that Noctis must be much older than Olympus Mons or the other Thasis volcanoes. Although its origins are likely ancient, there are signs of relatively recent activity – and the discoverers are not ruling out that the volcano could erupt again.

As a location with clear water and most likely residual heat, Noctis may be one of the best opportunities to find life on Mars.

The discovery of the volcanoes on Mars was a dramatic moment in the exploration of the solar system. Mariner 9 and the Russian probes Mars 2 and Mars 3 all arrived during a planet-wide dust storm, and initially almost no detail was visible on the surface. As the dust settled, the massive volcanoes – the largest in the solar system – were the first features to emerge, giving an indication of how rich Mars is geologically.

Noctis Volcano is near the starting point of the Valles Mariners, a 2,500-mile-long gorge that could be Arizona’s version of the whole and barely noticeable. As such, it was already on a list of places NASA was keen to send a rover to. That priority has just been increased.

When it comes to human landing sites, a spot with easy access to (frozen) water near the equator meets some of the most important requirements.

The discovery was presented at the 55e Lunar and Planetary Science Conference with accompanying article available online.

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