Moon Science: Silicic Volcanoes | NASA's Lunar Reconnaissance Orbiter

Moon Science: Silicic Volcanoes | NASA's Lunar Reconnaissance Orbiter

The silicic volcano Mairan T (41.79°N, 311.61°E) stands over 600 meters tall and in stark albedo contrast to the surrounding dark mare basalts of Oceanus Procellarum. The view is from west-to-east and this scene is 6.6 kilometers wide.

Oceanus Procellarum is a vast lunar mare on the western edge of the near side of the Moon. It is the only one of the lunar maria to be called an "Oceanus" (ocean), due to its size. Oceanus Procellarum is the largest of the maria ("seas"), stretching more than 2,500 km (1,600 mi) across its north–south axis and covering roughly 4,000,000 km2 (1,500,000 sq mi), accounting for 10.5% of the Moon's total surface area.

The Mairan T dome is a large silicic volcanic structure with a pronounced summit depression. Remote sensing indicates that the composition of the volcanic material (lava) making up the dome is enriched in silica (SiO2). This rock type would be classified as either rhyolite or dacite on Earth, and the composition starkly contrasts with the dark, iron-rich mare basalts that embay the Mairan T dome. Most of the volcanism on the Moon is basaltic or iron-rich. Still, silicic volcanism also occurred on the Moon. Indeed, bits and pieces of similar materials were found in the Apollo samples; however, all are small fragments delivered to the Apollo sites as material ejected from distant impact events. One of the great questions for lunar science is how the silicic materials formed. On Earth, specific tectonic settings and higher water contents in the rocks favor the formation of such lavas; however, the Moon lacks plate tectonics and water-rich sediments. NASA is planning a Commercial Lunar Payload Services (CLPS) lander mission to another, larger silicic volcano, one of the Gruithuisen domes, to address this question.  

The Mairan T dome formed before the emplacement of the surrounding mare basalts. The large central depression represents the collapse of the central vent during the final stages of eruption. The volcano may also have spewed material—ash and dust—over the surrounding plains, but evidence of such erupted materials, known as pyroclastic deposits, would have been long since covered over by the basaltic lavas. Since then, continued degradation of the steep slopes of the cone by small impact events has spread silicic materials out onto the nearby basaltic plains. Explore this magnificent oblique view and see if you can find evidence for this late-stage mass wasting.

This year, NASA's Lunar Reconnaissance Orbiter (LRO) celebrates its 16th anniversary orbiting the Moon (2009-2026). This mission has given scientists the largest volume of data ever collected by a planetary science mission at NASA. Considering that success and the continuing functionality of the spacecraft and its instruments, NASA awarded the mission an extended mission phase to continue operations. LRO continues to be one of NASA's most valuable tools for advancing lunar science.

Learn more about NASA's LRO:
https://science.nasa.gov/mission/lro/

Image Credit: NASA/GSFC/Arizona State University, NAC M1387416559LR 
Text Credit: Mark Robinson
Release Date: Oct. 11, 2022

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