https://phys.org/news/2024-03-giant-volcano-mars.html
by Rebecca McDonald, SETI Institute
In a groundbreaking announcement at the 55th Lunar and Planetary Science Conference held in The Woodlands, Texas, scientists revealed the discovery of a giant volcano and possible sheet of buried glacier ice in the eastern part of Mars' Tharsis volcanic province near the planet's equator.
Imaged repeatedly by orbiting spacecraft around Mars since Mariner 9 in 1971—but deeply eroded beyond easy recognition, the giant volcano had been hiding in plain sight for decades in one of Mars' most iconic regions, 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).
Provisionally designated "Noctis volcano" pending an official name, the structure is centered at 7° 35' S, 93° 55' W. It reaches +9022 meters (29,600 feet) in elevation and spans 450 kilometers (280 miles) in width. The volcano's gigantic size and complex modification history indicate that it has been active for a very long time. In its southeastern part lies a thin, recent volcanic deposit beneath which glacier ice is likely still present.