Active Tectonic System Spotted on Moon’s Nearside | Planetary Science, Space Exploration – Sci-News.com

A system of wrinkle ridges on the nearside maria of the Moon is evidence of seismic activity set in motion 4.3 billion years ago that could be ongoing today, according to new research.

Global map of the albedo from the 750 nm filter of the UV-VIS camera onboard NASAs Clementine spacecraft. The image shows the near side and far side of the Moon in Lambert, equal-area projection. Image credit: NASA.

Most of the Moons surface is covered by regolith, a powdery blanket of ground-up rock created by the constant bombardment of tiny meteorites and other impactors.

Areas free of regolith where the lunar bedrock is exposed are vanishingly rare.

But University of Bern researcher Adomas Valantinas and Brown Universitys Professor Peter Schultz used data from NASAs Lunar Reconnaissance Orbiter to spot strange bare spots within and surrounding the lunar maria.

Exposed blocks on the surface have a relatively short lifetime because the regolith buildup is happening constantly, Professor Schultz said.

So when we see them, there needs to be some explanation for how and why they were exposed in certain locations.

For the study, the scientists used the Diviner Lunar Radiometer Experiment (DLRE), an instrument aboard the Lunar Reconnaissance Orbiter that measures the temperature of the lunar surface.

Just as concrete-covered cities on Earth retain more heat than the countryside, exposed bedrock and blocky surfaces on the Moon stays warmer through the lunar night than regolith-covered surfaces.

Using nighttime observations from DLRE, the team turned up more than 500 patches of exposed bedrock on narrow ridges following a pattern across the lunar nearside maria.

A few ridges topped with exposed bedrock had been seen before. But those ridges were on the edges of ancient lava-filled impact basins and could be explained by continued sagging in response to weight caused by the lava fill, Professor Schultz said.

But this new study discovered that the most active ridges are related to a mysterious system of tectonic features (ridges and faults) on the lunar nearside, unrelated to both lava-filled basins and other young faults that crisscross the highlands.

The distribution that we found here begs for a different explanation.

Infrared (upper left) and other images from NASAs Lunar Reconnaissance Orbiter revealed strange bare spots where the Moons ubiquitous dust is missing. Image credit: Valantinas & Schultz, doi: 10.1130/G47202.1.

Valantinas and Professor Schultz mapped out all of the exposures revealed in the DLRE data and found an interesting correlation.

In 2014, NASAs Gravity Recovery and Interior Laboratory (GRAIL) mission found a network of ancient cracks in the Moons crust. Those cracks became channels through which magma flowed to the lunar surface to form deep intrusions.

The study authors showed that the blocky ridges seemed to line up just about perfectly with the deep intrusions revealed by GRAIL.

Its almost a one-to-one correlation. That makes us think that what were seeing is an ongoing process driven by things happening in the Moons interior, Professor Schultz said.

The researchers suggest that the ridges above these ancient intrusions are still heaving upward.

The upward movement breaks the surface and enables regolith to drain into cracks and voids, leaving the blocks exposed.

Because bare spots on the Moon get covered over fairly quickly, this cracking must be quite recent, possibly even ongoing today.

They refer to what theyve found as the Active Nearside Tectonic System (ANTS).

They believe that the ANTS was actually set in motion billions of years ago with a giant impact on the Moons farside.

In previous studies, they proposed this impact, which formed the South Pole Aitken Basin, shattered the interior on the opposite side, the nearside facing the Earth.

Magma then filled these cracks and controlled the pattern of dikes detected in the GRAIL mission.

The blocky ridges comprising the ANTS now trace the continuing adjustments along these ancient weaknesses.

This looks like the ridges responded to something that happened 4.3 billion years ago, Professor Schultz said.

Giant impacts have long lasting effects. The Moon has a long memory. What were seeing on the surface today is testimony to its long memory and secrets it still holds.

The study was published in the journal Geology.

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A. Valantinas & P.H. Schultz. The origin of neotectonics on the lunar nearside. Geology, published online April 13, 2020; doi: 10.1130/G47202.1

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Active Tectonic System Spotted on Moon's Nearside | Planetary Science, Space Exploration - Sci-News.com