China is in the middle of a multi-part mission to explore the moon with unmanned landers, the most recent of which is Chang’e-4. This intrepid little probe made history when it became the first object to make a soft landing on the far side of the moon. Now, it’s busily taking measurements and sending them back to Earth. According to the China National Space Administration (CNSA), Chang’e-4 has found the moon to be more frigid than expected. Hopefully, it packed a blanket.
While we often hear the far side of the moon referred to as the “dark side,” that’s an inaccurate description. This side faces away from Earth, but it gets plenty of sunlight as Earth and the moon (which is tidally locked) rotate. Landing on the far side is a significant challenge not because it’s dark, but because there’s no direct line of sight to Earth. The entire landing needs to be automated, and Chang’e-4 nailed it.
Shortly after landing on January 3rd, Chang’e-4 deployed the Yutu-2 rover. Following that, the CNSA put Chang’e-4 into sleep mode for two weeks during the lunar night. When the probe came back online, it reported to ground control the temperatures it experienced on the far side of the moon. Let’s just say the moon isn’t an ideal vacation spot. Chang’e-4 saw temperatures go as low as -310 degrees Fahrenheit (-190 degrees Celsius).
Chang’e-4 deployed the Yutu-2 rover several hours after landing on the moon’s far side.
Before Chang’e-4, scientists generally considered -280 degrees Fahrenheit to be the low for the moon. However, those readings all came from the near side of the moon. As we already covered, the far side of the moon is not permanently shrouded in darkness, so what gives? The initial hypothesis from the Chang’e team is that the differing composition of lunar soil on the far side could be responsible for the colder temperatures.
Yutu-2 might be able to clear things up as its mission continues. The rover includes a Visible and Near-Infrared Imaging Spectrometer (VNIS) capable of identifying surface materials and trace atmospheric gasses. The CNSA designed the rover to operate for at least three months and the lander for a year. The last Chang’e lander started to degrade right around of the primary mission, so don’t expect this lander to produce new discoveries for years to come.