Chang'e-4's Yutu-2 Rover Reveals Hidden Layers of the Moon's History with Lunar Penetrating Radar

China's Chang'e-4 spacecraft, a pioneering achievement as the first to touch down on the farside of the Moon in 2018, has captured remarkable panoramic views of impact craters and collected samples from the lunar mantle.

Researchers recently reported in their paper, titled "Layered Structures in the Upper Several Hundred Meters of the Moon Along the Chang'E-4 Rover's First 1,000-m Traverse" published in the Journal of Geophysical Research, that the spacecraft's rover mapped 1,000 feet (300 meters) of the Moon's hidden structure below, offering a level of detail previously unattainable.

(Photo : Unsplash/Mike Petrucci)
Chang'e-4's Yutu-2 Rover Reveals Hidden Layers of the Moon's History with Lunar Penetrating Radar

China's Rover Finds Massive Crater Under Layers of Soil, Rocks

Aboard the Chang'e-4 spacecraft is the Yutu-2 rover equipped with Lunar Penetrating Radar (LPR) to transmit radio signals into the Moon's depths. Lead researcher Jianqing Feng explained that the device captures returning echoes, aiding in creating a subsurface map.

Yutu-2 used LPR in 2020 to chart the upper 130 feet of the Moon's surface, later revealing diverse layers of dust, soil, and broken rocks, hiding a crater and underlying lava formations and uncovering lunar history. The team believes that the rubble surroundings were a result of ejecta.

Around 4.51 billion years ago, shortly after the birth of the Solar System, experts believe the Moon originated when a Mars-sized body collided with Earth, resulting in the detachment of a fragment. Over approximately 200 million years, the Moon experienced a barrage of cosmic impacts, some of which fractured its surface.

Analogous to Earth, the Moon's mantle harbored molten pockets named magma, which flowed out through fresh crevices, giving rise to a sequence of volcanic outbursts, according to Feng's explanation.

Chang'e-4's new findings reveal a waning volcanic process: layers of volcanic rock thin closer to the moon's surface, indicating decreased lava flow in later eruptions. This suggests the moon cooled and lost energy over time.

Moon's volcanic activity likely ceased around 1 billion years ago, though some evidence of more recent activity exists. Despite being termed "geologically dead," there might still be concealed magma beneath the lunar surface. But Chang'e-4's lunar mission is not yet complete as it will continue its mission of revealing unforeseen geological structures on the farside of the Moon.

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Weird Side of the Moon

Unlike the Moon's visible near side, its farside holds significant differences due to its unique geologic activity. Robotic missions and Apollo expeditions over the last 60 years have unveiled divergent features, with only about 1% of the far side covered by volcanic maria compared to 31% on the near side.

A collaborative study in 2020 involving researchers from multiple institutions including the Tokyo Institute of Technology, University of Florida, Carnegie Institution for Science, Towson University, NASA Johnson Space Center, and University of New Mexico, delved into the moon's geological history, offering a fresh rationale for the distinction between its near and far sides.

By combining experiments, computer simulations, and existing lunar surface observations, the team proposed that variations in radioactive element concentrations, such as Potassium (K), thorium (Th), and uranium (U), contribute to the dissimilarity. These elements, undergoing radioactive decay, generate heat capable of melting rocks in their vicinity.

This study reveals that alongside heat generated by radioactive decay, KREEP-enriched material on the moon's surface with lower melting points has contributed to anticipated geological transformations, suggesting that these factors have been shaping the lunar landscape since its formation billions of years ago.

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