'Dark' Side Of Moon Mystery: Chang'e-4 Discovers Surprising Temperature Drop During Lunar Night

The "dark" side of the Moon may never become an ideal place to live in, despite plans for an international research base in the future, as the Chinese probe Chang'e-4 just revealed that the lunar surface is far colder than expected.

The Chang'e-4, which made its historic landing on the far side of the Moon on Jan. 3, discovered that surface temperature plummeted to minus 310 Fahrenheit (minus 190 degrees Celsius) during the lunar night. The lander and its rover, Yutu 2 (Jade Rabbit 2), sent back data about the lunar temperature after they were woken up by sunlight at the end of January following their first freezing night on the Moon, China National Space Administration confirmed via Xinhua. The probe and its rover had been "sleeping," which meant it was on dormant mode, due to lack of solar power during the 14-day lunar night.

Previous Apollo missions revealed that the Moon's surface temperature could reach up to 260 degrees Fahrenheit (127 degrees Celsius) during the day and drop to minus 280 Fahrenheit (minus 173 Celsius) during the lunar night. However, this data comes from the side of the satellite that faces Earth. The new data from Chang'e-4, however, sheds light on what happens during the night on the "dark" side, the part of the Moon that we don't see from Earth.

The reason why we only ever see one side of the Moon is that the Earth's natural satellite is tidally-locked to the planet. The Moon continues to spin in order to constantly show one side at the Earth, however, so it experiences days and nights from the varying sunlight. Each day and night on the Moon lasts about two Earth-weeks.

Zhang He, executive director of the Chang'e-4 probe project, from the China Academy of Space Technology (CAST), explained the difference between the data from the Apollo mission and Chang'e-4's discovery. He revealed that there may be something in the lunar dirt on the far side of the Moon that causes it to retain less heat overnight compared to the areas explored by the Apollo.

"According to the measurements of Chang'e-4, the temperature of the shallow layer of the lunar soil on the far side of the moon is lower than the data obtained by the U.S. Apollo mission on the near side of the moon," Zhang said. "That's probably due to the difference in lunar soil composition between the two sides of the moon. We still need more careful analysis."

This was the first time that Chinese scientists got first-hand data about the temperature on the Moon. Before Chang'e-4, China launched Chang'e-3, the first probe from the country to soft-land on the satellite, back in 2013. However, the spacecraft was designed with foreign temperature in mind, not that of the lunar surface. Still, the lander continues to operate despite having experienced over 60 lunar nights in the span of five years.