China’s pioneering mission to explore the far side of the Moon continues to shed new light on this relatively unknown territory, with scientists using instruments aboard the unmanned Chang'e-4 spacecraft to peek beneath the surface for the first time. The probe's rover module has used onboard radar to penetrate deep into the Moon to help scientists build a picture of the subsurface structure, offering new clues on its turbulent history.

As a successor to Chang'e-3 which visited the Moon in 2013, Chang'e-4 made history by touching down on the lunar far side in January last year, the first spacecraft ever to do so. It is thought that this area is home to ancient water ice deposits, preserved through a lack of direct sunlight, while the mission will also study the composition of the lunar crust and mantle, ultimately furthering our understanding of how the Moon was formed billions of years ago.

As part of this brief, the probe’s Yutu-2 rover is equipped with a Lunar Penetrating Radar, which is designed to send radio signals deep into the Moon’s surface to investigate the layers down below. The team reports that this piece of machinery is functioning particularly well, with the forgiving landscape allowing the radar signals to reach depths of 40 meters (131 ft), around three times those achieved by Chang’E-3.

"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," says 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."

A radar aboard the Yutu-2 rover has helped scientists piece together the layers beneath the far side of the moon CLEP/CRAS/NAOC

These radar images were gathered over two days and provide the first electromagnetic image of the subsurface structure of the Moon’s far side. Combining them with tomographic data and the other analysis, the team was able to start piecing together the composition of the subsurface, concluding that it is made up of highly porous granular materials and boulders of varying sizes. The scientists believe this is the result of the Moon’s violent past, where meteors and other debris would regularly slam into the surface and eject materials to other regions.

"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 says. "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."

The research was published in the journal Science Advances.

Source: Chinese Academy of Sciences via Phys.org