Author: Lisa Grossman / Source: Science News
China is about to make space history.
In December, the country will launch the first spacecraft ever to land on the farside of the moon. Another craft, slated for takeoff in 2019, will be the first to bring lunar rocks back to Earth since 1976.These two missions — the latest in China’s lunar exploration series named after the Chinese moon goddess, Chang’e — are at the forefront of renewed interest in exploring our nearest celestial body. India’s space agency as well as private companies based in Israel and Germany are also hoping for robotic lunar missions in 2019. And the United States aims to have astronauts orbiting the moon starting in 2023 and to land astronauts on the lunar surface in the late 2020s.
The time is ripe for new lunar exploration. Despite decades of study, Earth’s only natural satellite still contains mysteries about its formation as well as clues to the history of the solar system (SN: 4/15/17, p. 18). “There are too many things we don’t know,” says planetary scientist Long Xiao of China University of Geosciences in Wuhan. He is a coauthor of two studies published in June and July in the Journal of Geophysical Research: Planets describing the landing sites of the new Chinese missions, Chang’e-4 and -5.
To figure out what secrets the moon may still be hiding, scientists are excited to get their hands on new rock samples. The Chang’e-5 sample return mission “no doubt will have additional rock types that we haven’t sampled yet,” says planetary scientist David Blewett of Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “If you came to the Earth and landed in Great Britain and made all your conclusions about the Earth from what you saw … you really wouldn’t have the whole picture.”
Journey to the dark side
The Chang’e-4 spacecraft includes a lander and a rover that were originally built as backups for the 2013 Chang’e-3 mission, which marked China’s first moon landing — and the first moon landing at all since the 1970s (SN Online: 12/16/13). The uncrewed Chang’e-3 lander-rover duo touched down in a vast lava plain in the north known as Mare Imbrium, where the craft measured the composition and thickness of the lunar soil and discovered what might be a new type of basalt, or lava-based rock.
This time, China has its sights set on lunar regions never before explored. Chang’e-4 is aiming for the moon’s largest, deepest and possibly oldest known feature created by an impact, the South Pole–Aitken basin, on the lunar farside, which always faces away from Earth. The whole basin, which is 2,500 kilometers wide and up to 8.2 kilometers deep, is too big for the rover to explore. So Chang’e-4 is shooting for the 186-kilometer-wide Von Kármán crater within the larger basin for a cosmic hole in one.
DARK AND DEEP
The enormous impact that formed the South Pole–Aitken basin is thought to have excavated parts of the lunar mantle, the once-molten layer of denser rock that sits below the crust. Exploring the crater could offer a window into the moon’s interior.
“There’s a big argument about the composition of the lunar mantle,” Xiao says. For instance, is the mantle “wet” and full of hydrated minerals, or dry? If it is wet, how did…
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