Marianne Dyson, November 2018
No spacecraft has ever landed on the lunar far side. The only human-made object on the far side currently is NASA’s Ranger 4 that crashed east of Korolev crater (about 15 degrees south of the equator) in April 1962. But that is about to change!
If all goes well this December, the Chinese Chang’E-4 (named after a mythological Moon goddess) will earn the title of first to the far side. This spacecraft is a lander/rover combination similar to the impressive 2013 Chinese lunar mission called Chang’E-3. Its Yutu (rabbit) rover successfully explored the Bay of Rainbows (Moon’s left “eyebrow”) and returned exciting new scientific data about the lunar surface and subsurface.
The far side of the Moon is never visible from Earth, making direct communications impossible. Therefore, to communicate with the spacecraft and rover on the surface, the Chinese deployed a relay satellite called Queqia (meaning “magpie bridge” from Chinese folklore) earlier this year. Since June, it has been in a 28-day orbit around the Earth-Moon L2 Lagrange point, which is about 37,000 miles (60,000 kilometers) beyond the Moon.
Chang’E-4’s landing area will be in Von Kármán Crater which is near the center of the far side and about 45 degrees south of the lunar equator. This crater lies on top what may be the most ancient preserved impact in the solar system, called the South Pole Aitkin (SPA) Basin. From orbit around the Moon, the SPA Basin appears as a large dark bruise that is more than 8 km (5 mi) deep and has a diameter of 2500 km (1550 mi) which is about a fourth of the Moon’s circumference. [Ref: NASA Lunar Reconnaissance Orbiter]
The floor of Von Kármán crater was selected because it is relatively flat, with no more than about 197 feet (60 meters) of elevation change in topography. The rover will map the thickness of the regolith (lunar soil) in this area, which should help researchers to date the age of Von Kármán’s formation and anchor a geological timeline for much of the lunar far side.
Several countries, though not the United States, are actively involved in Chang’E-4. Germany is providing a lunar neutron and radiation dose detector for the lander, Sweden is contributing a neutral atom detector for the rover, and the Netherlands provided a low-frequency radio spectrometer for the Queqia relay satellite.
Dr. Jun Huang of the Planetary Sciences Institute, China University of Geosciences in Wuhan noted that one of the public education experiments on the lander will concern studying a tiny ecosystem including vegetables and worms. These items will be the first non-human living things (other than bacteria left behind on spacecraft) to reach the surface of the Moon.
But perhaps the most exciting thing about this first exploration of the lunar far side is that the Chinese have embarked on a well-planned step-by-step approach to building space capabilities that will directly lead to human space settlements. After Chang’E-4 comes Chang’E-5, an ambitious lunar sample return.
After that, they will use robotic missions to further explore the lunar far side south polar region. Their 10-year plan, which they have followed very closely, has these missions launching in 2023 with humans arriving as soon as 2030. While NASA’s attention is focused on space stations in high lunar orbits, the Chinese may become not only the first to land a spacecraft on the far side, but humans, too.
Writing about Space
My article, “Chinese Planetary Exploration Plans” with more detail about the Chinese space program is in the 2018-4 (current) issue of Ad Astra magazine. To get your copy, join NSS!
To the Moon and Back: My Apollo 11 Adventure, a pop-up book coauthored with Buzz Aldrin with art by Bruce Foster, is available for now from Amazon. Get one for all the kids, big and small, in your family!
My science fact article, “In Defense of the Planet,” is in the Nov/Dec 2018 issue of Analog. Paper or eBook subscriptions available.