Digging into the far side of the moon: Chang'E-4 probes 40 meters into lunar surface

February 26, 2020

A little over a year after landing, China's spacecraft Chang'E-4 is continuing to unveil secrets from the far side of the Moon. The latest study, published on Feb.26 in Science Advances, reveals what lurks below the surface.

Chang'E-4 (CE-4) landed on the eastern floor of the Van Kármán crater, near the Moon's south pole, on Jan. 3, 2019. The spacecraft immediately deployed its Yutu-2 rover, which uses Lunar Penetrating Radar (LPR) to investigate the underground it roams.

"We found that the signal penetration at the CE-4 site is much greater than that measured by the previous spacecraft, Chang'E-3, at its near-side landing site," said paper author LI Chunlai, a research professor and deputy director-general of the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC). "The subsurface at the CE-4 landing site is much more transparent to radio waves, and this qualitative observation suggests a totally different geological context for the two landing sites."

LI and his team used the LPR to send radio signals deep into the surface of the moon, reaching a depth of 40 meters by the high frequency channel of 500 MHz - more than three times the depth previously reached by CE-3. This data allowed the researchers to develop an approximate image of the subsurface stratigraphy.

"Despite the good quality of the radar image along the rover route at the distance of about 106 meters, the complexity of the spatial distribution and shape of the radar features make identification of the geological structures and events that generated such features quite difficult," said SU Yan, a corresponding author who is also affiliated with NAOC.

The researchers combined the radar image with tomographic data and quantitative analysis of the subsurface. They concluded that the subsurface is essentially made by highly porous granular materials embedding boulders of different sizes. The content is likely the result of a turbulent early galaxy, when meteors and other space debris frequently struck the Moon. The impact site would eject material to other areas, creating a cratered surface atop a subsurface with varying layers.

The results of the radar data collected by the LPR during the first 2 days of lunar operation provide the first electromagnetic image of the far side subsurface structure and the first 'ground truth' of the stratigraphic architecture of an ejecta deposit.

"The results illustrate, in an unprecedented way, the spatial distribution of the different products that contribute to from the ejecta sequence and their geometrical characteristics," LI said, referring to the material ejected at each impact. "This work shows the extensive use of the LPR could greatly improve our understanding of the history of lunar impact and volcanism and could shed new light on the comprehension of the geological evolution of the Moon's far side."
This work was a collaboration with the Key Laboratory of Lunar and Deep Space Exploration at NAOC, the University of the Chinese Academy of Sciences, the Mathematics and Physics Department of Roma Tre University in Italy, the School of Atmospheric Sciences at the Sun Yat-sen University, and the Insituto per il Rilevamento Elettromagnetico dell'Ambiente IREA-CNR in Italy.

Chinese Academy of Sciences Headquarters

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.