Volcanism on the Moon
Volcanism on the Moon is represented by the presence of volcanoes, pyroclastic deposits and vast lava plains on the lunar surface.
Calderas, large-scale collapse features generally formed late in a volcanic eruptive episode, are exceptionally rare on the Moon.
Lunar lava plains cover large swaths of the Moon's surface and consist mainly of voluminous basaltic flows.
In 1610, Italian astronomer Galileo Galilei misinterpreted the lunar lava plains as seas while observing the Moon through an early telescope.
The bowl-shaped depressions distributed throughout the lunar landscape were first suggested to be volcanoes in 1665 by British chemist Robert Hooke.
French astronomer Pierre Puiseux proposed that the Moon's craters were collapsed volcanic domes that had vented all their gases.
Pierre-Simon Laplace, another French astronomer, proposed in the 18th century that meteorites were volcanic projectiles ejected from lunar craters during major eruptions.
[1] British astronomer William Herschel, in one of his early papers, claimed to have seen three volcanoes on the Moon in the late 1700s, which later turned out to be earthshine.
[3] In contrast, positive topographic features such as domes, cones and shields represent only a tiny fraction of the lunar volcanic record.
The reason that the mare basalts are predominantly located on the near-side hemisphere of the Moon is still being debated by the scientific community.
Based on data obtained from the Lunar Prospector mission, it appears that a large proportion of the Moon's inventory of heat producing elements (in the form of KREEP) is located within the regions of Oceanus Procellarum and the Imbrium basin, a unique geochemical province now referred to as the Procellarum KREEP Terrane.
[33] Because gravity on the Moon is only one sixth of that on Earth, lunar volcanism is capable of throwing ejecta much further, leaving little to pile up near the vent.
[34][35] They consist of several cones and domes that occupy the summit of a broad topographic swell, which may be the lunar equivalent of a shield volcano.
Three main basalt units ranging in age from 3.51 to 3.71 billion years have been identified at Mons Rümker, although the youngest volcanic features may be steep-sided domes on the plateau surface as they show indications of having been active until the Eratosthenian.
[38] Mons Hansteen, a roughly triangular-shaped dome on the southern margin of Oceanus Procellerum, is another example of a rare non-basaltic lunar volcano.
It consists of high-silica material that was erupted roughly 3.5 to 3.7 billion years ago from vents along northeast, northwest and southwest-trending fractures.
It differs from other lunar volcanic features due to its evolved lithology, regional tectonic setting, its location being near the north pole, far from the Procellarum KREEP Terrane and its recent association with endogenic water.
Their existence is sometimes revealed by the presence of a "skylight", a place in which the roof of the tube has collapsed, leaving a circular hole that can be observed by lunar orbiters.
[44][47] In 2023–2024, radar imaging of the Mare Tranquillitatis pit crater from NASA's Lunar Reconnaissance Orbiter was analyzed and determined to have been formed by the collapse of a lava tube that resulted in the formation of a cave conduit at least tens of meters long, proving the existence of lunar caves.
[55] Many smaller pyroclastic deposits measure only a few kilometers in diameter and are almost always located near the mare or in large impact crater floors, although several also lie along clear fault lines.
[56] Extending about 7 km (4.3 mi) east-southeast from the CBVC is a highly reflective area that may be a pyroclastic flow deposit.
The large extent of this pyroclastic deposit is due to the Moon's low gravity, such that a giant explosive eruption from the CBVC was able to spread debris over an area much greater than would be possible on Earth.
[66][67][68][69] Just prior to this, evidence has been presented for 2–10 million years younger basaltic volcanism inside the crater Lowell,[70][71] located in the transition zone between the near and far sides of the Moon.
[72][73] There are currently no active volcanoes on the Moon, although moonquake data published in 2012 suggest that there is a substantial amount of magma under the lunar surface.
