Complex crater on the summit of "north spot" volcano, Ascraeus Mons, appears in this photograph taken Dec. 17, 1971. The darkest parts of the rim are most free of dust; lower lands of the mountain are obscured by bright dust clouds.

Ascraeus Mons is a large shield volcano located in the Tharsis region of the planet Mars. It is the northernmost and tallest of three shield volcanoes collectively known as the Tharsis Montes. Ascraeus Mons was discovered by the Mariner 9 spacecraft in 1971. The volcano was originally called North Spot because it was the northernmost of only four spots visible on the surface due to a global dust storm that was then enshrouding the planet. As the dust cleared, the spots were revealed to be extremely tall volcanoes whose summits had projected above the dust-laden, lower atmosphere. The volcano’s name officially became Ascraeus Mons in 1973.

Mariner 9 was launched on May 30, 1971 and arrived on November 14, 1971.

Photojournal Note: This caption was updated on January 9, 2017. The image title has also been changed to reflect the official volcano name of Ascraes Mons, correcting the previous Olympus Mons.