China’s Rover Finds That Regolith on the Moon’s far-Side is Stickier Than the Near-Side

We’re never able to see the far side of the moon from the Earth, but that doesn’t mean it’s that different.  Recently rovers and satellites have started exploring the lesser-known side of the moon.  They found a slightly different geology than that discovered on the near side, which might have implications for navigating the far side in the future.

China’s Chang’E-4 mission landed on the far side of the moon over three years ago in humanity’s first successful attempt at doing so.  Since then, it has been trundling around the surface, making discoveries such as a strange-looking rock and some of the moon’s mantle on its surface.  

A map of the path the rover has taken, as well as the wheel slippage rates on each day of travel.
Credit – Ding et al.

Now a new paper discusses a topic that is an unusual data source – how the Yutu-2 rover that is part of the Chang’E-4 mission has been moving.  Published in Science Robotics, the paper discusses the various trials and tribulations that the rover has experienced while navigating a side of the moon that radio signals from Earth cannot directly reach.

The signal bouncing required to communicate Yutu-2 hasn’t slowed the rover down, though.  What has slowed it down is its wheels slipping and sliding in some spots and getting clogged with dirt in others.  Yutu-2 appears to be navigating a series of gentle slopes that regularly cause slight slippage of its wheels, which is caused by material similar in texture to sandy loam on Earth.

An example of some of the cohesive regolith that stuck to the rover’s wheels.
Credit – Ding et al.

Even with all the slipping and sliding, there have been noticeably more dirt clumps attaching themselves to the rover’s wheels than there have been at other lunar landing sites.  This would imply a slightly higher cohesion to the regolith than the near side.  There could be several different explanations for this, including the far side getting blasted by more solar radiation or something local to the geology of the far side region.`

Other exciting finds include small impact craters along the route Yutu-2 took, some of which had markings that indicated “secondary impact events.”  Those happen when a meteorite or other small object impacts in a larger crater that was previously formed. In addition, some of the material at the bottoms of those craters were a “high reflectance,” making them attractive to any future explorers.

Open Space forum about China’s plans for the moon.

Ultimately, the differences between what Yutu-2 has found on the far side and what Apollo and other missions located on the near side were relatively minor.  The moon appears to be the moon, no matter what side you’re on.  That makes it slightly easier for any future human explorers, but there might still be some other mysteries on the far side to unlock – if only humanity sends some more explorers there.

Learn More:
Science Robotics – A 2-year locomotive exploration and scientific investigation of the lunar farside by the Yutu-2 rover
New Scientist – Yutu-2 lunar rover finds sticky soil on the far side of the moon – The Moon’s farside has sticky soil, Yutu-2 finds
UT – China’s Yutu-2 Rover has now Traveled Over 345 Meters Across the Surface of the Moon

Lead Image:
Image of the Yutu-2 rover from the Chang’E 4 mission
Credit – CNSA