Lunar radar data uncovers new clues about moon's ancient past

Date:
December 1, 2021
Source:
Penn State
Summary:
The dusty surface of the moon -- immortalized in images of Apollo
astronauts' lunar footprints -- formed as the result of asteroid
impacts and the harsh environment of space breaking down rock over
millions of years. An ancient layer of this material, covered
by periodic lava flows and now buried under the lunar surface,
could provide new insight into the Moon's deep past, according to
a team of scientists.



FULL STORY ==========================================================================
The dusty surface of the moon -- immortalized in images of Apollo
astronauts' lunar footprints -- formed as the result of asteroid impacts
and the harsh environment of space breaking down rock over millions of
years. An ancient layer of this material, covered by periodic lava flows
and now buried under the lunar surface, could provide new insight into
the Moon's deep past, according to a team of scientists.


========================================================================== "Using careful data processing, we found interesting new evidence
that this buried layer, called paleoregolith, may be much thicker than previously expected," said Tieyuan Zhu, assistant professor of geophysics
at Penn State.

"These layers have been undisturbed since their formation and could be important records for determining early asteroid impact and volcanic
history of the moon." The team, led by Zhu, conducted new analysis
of radar data collected by China's Chang'e 3 mission in 2013, which
performed the first direct ground radar measurements on the moon.

The researchers identified a thick layer of paleoregolith, roughly 16
to 30 feet, sandwiched between two layers of lava rock believed to be
2.3 and 3.6 billion years old. The findings suggest the paleoregolith
formed much faster than previous estimates of 6.5 feet per billion years,
the scientists said.

The moon has experienced volcanic activity throughout its history,
depositing lava rock on the surface. Over time, the rock breaks down
into dust and soil, called regolith, with repeated asteroid impacts
and space weathering, only to be buried by subsequent lava flows, the scientists said.

"Lunar scientists count craters on the moon and use computer models
to determine the rate that regolith is produced," Zhu said. "Our
findings provide a constraint on what happened between two and three
billion years ago. This is the very unique contribution of this work."
Previous studies have examined the dataset, created when the Yutu rover
sent electromagnetic pulses into the lunar underground and listened as
they echoed back. Zhu said his team developed a four-step data processing
flow to enhance the signal and suppress noise in the data.



==========================================================================
The scientists observed changes in polarity as the electromagnetic
pulses traveled down through the dense lava rock and the paleoregolith, allowing the team to distinguish between the different layers.

"Our paper is really providing the first geophysical evidence to see
this electromagnetic permittivity changed from a small value for the paleoregolith to a large value for the lava flows," Zhu said. "We
discovered this polarity change in the data and created a detailed
geophysical image of the subsurface up to a few hundred meters depth."
The results may indicate higher meteoric activity in the solar system
during this period billions of years ago, according to the team, who
recently reported their findings in the journal Geophysical Research
Letters.

Zhu said the data processing tools may have use for interpreting similar
data collected during future missions to the moon, Mars or elsewhere in
the solar system. His team is now working with machine learning technology
to further improve the findings.

"I would say we used traditional data processing techniques, but we looked
at the data with more care and designed its suitable workflow for such
lunar data because this is a very different environment than Earth," Zhu
said. "Here at Penn State, we already made this workflow as an open-source
code for colleagues." Jinhai Zhang and Yangting Lin, professors at the
Chinese Academy of Sciences, contributed to this research.

========================================================================== Story Source: Materials provided by Penn_State. Original written by
Matthew Carroll. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Tieyuan Zhu, Jinhai Zhang, Yangting Lin. Ultra‐Thick
Paleoregolith
Layer Detected by Lunar Penetrating Radar: Implication for Fast
Regolith Formation Between 3.6 and 2.35 Ga. Geophysical Research
Letters, 2021; 48 (20) DOI: 10.1029/2021GL095282 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211201145304.htm

--- up 2 weeks, 6 days, 2 hours, 55 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)