Research reveals possibly active tectonic system on the Moon

April 30, 2020

PROVIDENCE, R.I. [Brown University] -- Researchers have discovered a system of ridges spread across the nearside of the Moon topped with freshly exposed boulders. The ridges could be evidence of active lunar tectonic processes, the researchers say, possibly the echo of a long-ago impact that nearly tore the Moon apart.

"There's this assumption that the Moon is long dead, but we keep finding that that's not the case," said Peter Schultz, a professor in Brown University's Department of Earth, Environmental and Planetary Sciences and co-author of the research, which is published in the journal Geology. "From this paper it appears that the Moon may still be creaking and cracking -- potentially in the present day -- and we can see the evidence on these ridges."

Most of the Moon's 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 Moon's bedrock is exposed are vanishingly rare. But Adomas Valantinas, a graduate student at the University of Bern who led the research while a visiting scholar at Brown, used data from NASA's Lunar Reconnaissance Orbiter (LRO) to spot strange bare spots within and surrounding the lunar maria, the large dark patches on the Moon's nearside.

"Exposed blocks on the surface have a relatively short lifetime because the regolith buildup is happening constantly," 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, Valantinas used the LRO's Diviner instrument, which 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 Diviner, Valantinas 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, Schultz says. 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. 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," Schultz said.

Valantinas and Schultz mapped out all of the exposures revealed in the Diviner data and found an interesting correlation. In 2014, NASA's GRAIL mission found a network of ancient cracks in the Moon's crust. Those cracks became channels through which magma flowed to the Moon's surface to form deep intrusions. Valantinas and Schultz showed that the blocky ridges seemed to line up just about perfectly with the deep intrusions revealed by GRAIL.

"It's almost a one-to-one correlation," Schultz said. "That makes us think that what we're seeing is an ongoing process driven by things happening in the Moon's interior."

Schultz and Valantinas suggest that the ridges above these ancient intrusions arestill 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 they've found as ANTS, for Active Nearside Tectonic System.

The researchers believe that the ANTS was actually set in motion billions of years ago with a giant impact on the Moon's farside. In previous studies, Schultz and a co-worker proposed this impact, which formed the 1500-mile 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," Schultz said. "Giant impacts have long lasting effects. The Moon has a long memory. What we're seeing on the surface today is testimony to its long memory and secrets it still holds."
-end-


Brown University

Related Moon Articles from Brightsurf:

New mineral discovered in moon meteorite
The high-pressure mineral Donwilhelmsite, recently discovered in the lunar meteorite Oued Awlitis 001 from Apollo missions, is important for understanding the inner structure of the earth.

First measurements of radiation levels on the moon
In the current issue (25 September) of the prestigious journal Science Advances, Chinese and German scientists report for the first time on time-resolved measurements of the radiation on the moon.

Researchers develop dustbuster for the moon
A team led by the University of Colorado Boulder is pioneering a new solution to the problem of spring cleaning on the moon: Why not zap away the grime using a beam of electrons?

First global map of rockfalls on the Moon
A research team from ETH Zurich and the Max Planck Institute for Solar System Research in Göttingen counted over 136,000 rockfalls on the moon caused by asteroid impacts.

Going nuclear on the moon and Mars
It might sound like science fiction, but scientists are preparing to build colonies on the moon and, eventually, Mars.

Astronaut urine to build moon bases
The modules that the major space agencies plan to erect on the Moon could incorporate an element contributed by the human colonizers themselves: the urea in their pee.

How moon jellyfish get about
With their translucent bells, moon jellyfish (Aurelia aurita) move around the oceans in a very efficient way.

Does crime increase when the moon is full?
Noting that anecdotal beliefs can affect public policies and practices, a 'pracademics' team from NYU's Marron Institute of Urban Management worked with public safety personnel to examine the commonly held axiom that crime rises with the full moon -- and found that the evidence is just not there.

Soil on moon and Mars likely to support crops
Researchers at Wageningen University & Research in the Netherlands have produced crops in Mars and moon soil simulant developed by NASA.

Are we prepared for a new era of field geology on the moon and beyond?
Space agencies must invest more resources on field geology training of astronauts to take full advantage of scientific opportunities on the moon and other planetary bodies, Kip Hodges and Harrison Schmitt urge, in an Editorial.

Read More: Moon News and Moon Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.