The rocks are probably leftover debris from when large asteroids and meteorites smashed into the moon’s surface, says Su. The layer below this, which extends to the radar’s penetration limit of 40 metres, is composed of alternating layers of coarse and fine soil.
The coarse layers are probably leftover debris from impacts, while the finer material probably formed via gradual weathering during the periods between each impact, says Su. The subsurface of the nearside of the moon was previously investigated by China’s Yutu rover, the predecessor of Yutu-2.
Deployed by China’s Chang’e 3 lander in 2013, it used high-frequency, ground-penetrating radar to explore a crater called Mare Imbrium.
“The subsurface structure at the Chang’e 4 landing site is more complex, and suggests a totally different geological context,” says Su. Yutu-2 is still travelling around the far side of the moon, and may be able to tell us more about what lies beneath by using low-frequency, ground-penetrating radar, which can see several hundred metres down, says Su.
The newcomer is a small asteroid that was apparently snagged in the Earth‘s orbit where it now exists as a temporary “mini-moon.” Scientists discovered the new moon last week but wanted to confirm that it wasn’t an artificial satellite or random space junk.
According to the astronomers, the Earth‘s new companion has an erratic orbit but there’s little cause for concern: it’s only about the size of compact car.
Scientists discovered another one 14 years ago and it’s logical to assume such events have occurred for as long as the Earth‘s been around.
Within a matter of months the new moon will break free of the Earth‘s grip and bid us all a fond farewell as it hurtles off into space to continue boldly going wherever asteroids go.
Over the next few days, researchers at six more observatories around the world watched the object, designated 2020 CD3, and calculated its orbit, confirming that it has been gravitationally bound to Earth for about three years.
An announcement posted by the Minor Planet Center, which monitors small bodies in space, states that “no link to a known artificial object has been found”, implying that it is most likely an asteroid caught by Earth’s gravity as it passed by.
This is just the second asteroid known to have been captured by our planet as a mini-moon – the first, 2006 RH120, hung around between September 2006 and June 2007 before escaping.
“It is heading away from the Earth-moon system as we speak,” says Grigori Fedorets at Queen’s University Belfast in the UK, and it looks likely it will escape in April.