India’s Chandrayaan-3 spacecraft stands on the brink of becoming the first scientific instrument to successfully survive the frigid night on the Moon without any heating equipment.
Following a groundbreaking two-week mission, India’s lander and rover have entered sleep mode in the cold darkness of the Moon’s south pole.
India has completed its landing mission and scientific research at the Moon’s south pole. (Photo: ISRO).
However, whether they will be able to “wake up” when the Sun shines again at the end of this lunar month remains a big question mark.
Surviving the Cold Darkness of the Moon
According to the Indian Space Research Organisation (ISRO), both the Vikram lander and the Pragyan rover of the Chandrayaan-3 mission were not equipped with the usual heating devices found in lunar missions.
This was an extremely risky decision, as temperatures near the Moon’s poles can drop to as low as -253°C, which is colder than some planets like Pluto.
The most common heating system used in spacecraft is called a Radioisotope Heater Unit (RHU), which operates by radiating heat passively to keep onboard hardware functioning stably over the long term without “freezing.”
Diagram of a Radioisotope Heater Unit. (Photo: Wikipedia).
Typically, RHUs are used in space missions to convert the heat generated from the natural decay of radioactive isotopes of plutonium or polonium into electrical energy.
This process ultimately warms the spacecraft’s equipment, or simply helps it survive extremely cold temperatures.
It is known that both halves of the Moon will experience 2 weeks of sunlight followed by 2 weeks of darkness.
As one approaches the poles, temperatures become more extreme due to the tilt and orbit, causing only the highest peaks to be illuminated by the Sun.
For this reason, RHUs have been used since early lunar landing missions in the 1970s.
Fragile Chances of Survival
Survival on the dark side of the Moon will be the next challenge for Chandrayaan-3. (Photo: NASA).
Historically, no instrument has survived a “cold winter” on the Moon without heating equipment. The widespread use of RHUs has made them a standard for space devices before deployment.
Lunokhod 1 (1970), Russia’s first lunar rover, traveled over 10 km in 10 months thanks to maintaining temperature and energy provided by a polonium-210 radioisotope heater.
Earlier, Apollo 11 (1969), which landed on the Moon, also used 34 grams of plutonium-238 to generate heat. China’s Chang’e-3 (2013) also had similar mechanisms to protect its systems from harsh lunar nights.
The Yutu rover from this mission survived its first night but lost mobility after the second night. Meanwhile, its successor, Yutu-2 (2018), was more successful, being able to wake up each time the Sun rose to continue its mission.
The Luna-25 lunar lander from Russia, launched on August 11, also had this heating system. Unfortunately, it encountered issues during landing and could not complete its mission.
Simulation of the Vikram lander and Pragyan rover from the Chandrayaan-3 mission. (Photo: ISRO).
As of now, ISRO has not publicly discussed why the Radioisotope Heater Units were not installed on the Vikram lander and the Pragyan rover of Chandrayaan-3. However, they have acknowledged that the duo will have to rely heavily on luck to survive the frigid darkness.
“If they cannot wake up, the Chandrayaan-3 lander will remain there as India’s lunar ambassador,” ISRO stated in a release. Nonetheless, the mission has been praised by the media as the “greatest scientific achievement” of India.
On the positive side, both devices from the Chandrayaan-3 mission have successfully achieved their scientific goals in what is sure to become a “hotspot” for human space exploration in the coming decade.
According to ISRO, the rover of the mission has traveled over 100 meters on the lunar surface, performing many critical tasks such as chemical analysis, thermal mapping of the upper layer of the regolith, and plasma measurements.
The scientific instruments of Chandrayaan-3 have also confirmed the presence of sulfur, iron, oxygen, and many other elements on the Moon.
It is expected that the Pragyan rover and Vikram lander will resume activities on September 22, coinciding with the next sunrise on the dark side of the Moon.
If successful, Chandrayaan-3 will set a new record by becoming the first scientific instrument to survive the frigid night on the Moon without any heating equipment.
