Humanity first visited the moon decades ago, but today is the first time a mission has made a soft landing on the moon’s far side. The Chinese Chang’e 4 probe set down in Von Kármán crater on January 3rd (Beijing time), marking another important milestone in the Chinese mission to explore the lunar surface.
The Chang’e 4 lander is the fourth of six planned lunar missions. It was initially constructed as a backup for Chang’e 3, which landed on the near side of the moon in 2013. That was China’s first moon landing and the beginning of its second mission phase. The first consisted of the lunar orbiters Chang’e 1 and 2. When Chang’e 3 landed successfully, the team set to work reconfiguring Chang’e 4 for its far side deployment.
We’ve never before landed a probe on the far side of the moon (sometimes incorrectly called the “dark side”) because it comes with its own unique challenges. You can’t send signals directly from the far side back to Earth because the surface points out into deep space. China prepared for this mission by deploying the Queqiao satellite in May 2018. Orbiting the Earth-Moon L2 Lagrangian point, Queqiao is in a position to relay data to and from the lander. However, the probe still needed autonomous landing systems with laser ranging and optical cameras. After setting down, it relayed the above photo.
The lander will remain stationary on the surface in a region known as the South Pole–Aitken basin. However, it also carried a six-wheeled rover that Chinese scientists will use to explore the far side of the moon. The rover is 3.3 feet across (1 meter) and weighs 310 pounds (140 kg), significantly smaller than NASA’s Mars-based Curiosity. The expected design lifetime is three months, but design refinements from the Chang’e 3 rover could make this one much more long-lived.
The Chang’e 4 mission carries a suite of instruments to study the moon itself and the space above it. Scientists believe the Aitken basin came into being billions of years ago after a large object collided with the moon and punched through its crust. That could mean material from the mantle exists on or near the surface. Chang’e 4 will measure the chemical composition of rocks and send that data back to Earth. It also includes instruments to monitor cosmic rays and observe the sun’s corona.
The next phase of China’s lunar exploration will kick off in late 2019 with the launch of Chang’e 5. This probe aims to return samples to Earth. If successful, this would be the first lunar sample return since the Soviet Luna 24 mission in 1976.
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