China achieved a space “first” tonight (January 2 Eastern Standard Time) landing the Chang’e-4 spacecraft on the far side of the Moon. The United States and Soviet Union landed many spacecraft on the near side, but no country has attempted a soft landing on the far side before. China’s CGTN tweeted the news just after 10:00 pm EST, but then deleted it for unknown reasons. China’s CCTV confirmed the landing in its 11:00 pm EST news program (12:00 noon January 3 in Beijing).

Chang’e-4 is the fourth in a series of robotic lunar spacecraft. Two other Chinese spacecraft also have been sent there, including a communications relay satellite, Queqiao, required to communicate between Earth and Chang’e-4 since there is no line-of-sight from the lunar far side to Earth. The far side always points away from Earth. Like the near side it gets 14 days of sunlight and 14 days of darkness.

Chang’e is China’s mythical goddess of the Moon.

Chang’e-1 and Chang’e-2 were orbiters. In 2013, Chang’e-3 became the first Chinese probe to land on the Moon along with its rover, Yutu. They are on the near side. Chang’e-4 was built as a backup, but although Yutu did not accomplish all of its objectives, China considers the mission a success and decided to repurpose Chang’e-4 for investigating the far side, a riskier mission.

Chang’e-4, launched on December 7, 2018, has its own rover. China has not yet revealed its name.

Both the lander and rover were modified to cope with the different environment on the lunar farside, which is more cratered than the nearside. The probe landed in the South Pole Aitken Basin, a site of considerable scientific interest. It is the oldest, largest and deepest impact basin on the Moon. It stretches across a quarter of the Moon and is 8 kilometers deep. Instruments on U.S. and Indian spacecraft have confirmed that water ice exists in permanently shadowed craters at both of the Moon’s poles, deposited by impacts from comets and asteroids over eons and preserved in the darkest and coldest locations.

Chang’e-4 landed at 10:26 am January 3 Beijing Time, which was 9:26 pm January 2 EST.

NASA Administrator Jim Bridenstine and Science Mission Directorate head Thomas Zurbuchen tweeted their congratulations after the landing was officially confirmed by China.

#Congratulations As part of the international science community, we look forward to learning about this rather unexplored part of our #Moon #exploration https://t.co/OlA8opFS9K — Thomas Zurbuchen (@Dr_ThomasZ) January 3, 2019

Soviet and American probes, including NASA’s Lunar Reconnaissance Orbiter (LRO) in orbit around the Moon since 2009, have sent back thousands of photos of the far side, but Chang’e-4 is the first to land there. LRO should be able to image Chang’e-4 on the surface.

China’s next robotic lunar probe, Chang’e-5, will be a sample return mission. China launched an engineering test in 2014 to return a canister to Earth from lunar distance as a step towards that goal. Chang’e-5 was intended to be launched in 2018, but it requires the Long March 5 rocket, which failed on its second flight in 2017. China hopes it will return to flight and Chang’e-5 will launch at some point in 2019.

The Soviet Union, United States, China, Japan, India, and the European Space Agency have sent probes to orbit the Moon. The first three of those countries also have soft-landed robotic probes, but the United States is the only country to send people there. From 1968-1972, two Apollo crews (Apollo 8 and Apollo 10) orbited the Moon and six more (Apollo 11, 12, 14, 15, 16 and 17) explored the lunar surface and brought back 842 pounds of lunar samples. Apollo 13 suffered an emergency during its flight to the Moon and swung around the far side, but did not go into orbit, and returned safely back on Earth.