India’s Chandrayaan-2 Is Ready to Touch Down Near the Moon’s South Pole

For the last two weeks, India’s Chandrayaan-2 spacecraft has been lowering its orbit around the moon as it prepares for India’s first attempt at a lunar landing. On Monday, the Chandrayaan-2 orbiter separated from the Vikram lunar lander, which was the last major maneuver before the scheduled landing on Friday. If successful, India will become just the fourth country to pull off a controlled landing on the moon.

The Vikram lander will use eight small thrusters, five rocket engines, and a suite of onboard cameras to autonomously guide itself to its landing location. The landing area is between two craters just 375 miles from the lunar south pole, which will make it the southernmost lunar landing in history.

Compared to the equatorial regions explored during the Apollo missions, little is known about the moon’s poles. Placing a lander on the surface is expected to generate a wealth of new information about the lunar environment in general and the nature of the moon’s water in particular.

Planetary scientists have long suspected that the moon’s south pole hosts an abundance of water ice in its permanently shadowed craters. But it wasn’t until India’s first Chandrayaan mission in 2008 that the existence of polar water ice was directly confirmed by a probe dropped to the lunar surface and an instrument on the orbiter. Lunar water ice can theoretically be used for life support and rocket fuel, which is a big part of why NASA wants to send humans to the moon’s south pole. But before we can start mining the moon for water, some big questions remain about the nature of the ice: Does it consist of small crystals or big blocks? Is it distributed across the surface or buried deep under the regolith? And how much ice is there on the moon anyway?

The Chandrayaan-2 mission could help answer these questions. “In many ways this is new territory,” says Dave Williams, a planetary scientist at NASA. “We’ve surveyed the moon pretty extensively from orbit, but there’s nothing like actually being there.”

Assuming a successful touchdown, about four hours later the Vikram lander will deploy Pragyan, a small, six-wheeled rover that will travel up to a half kilometer. The rover will use its cameras and two instruments to analyze the chemical composition of the lunar soil. Its lifespan will be short: The solar-powered rover is only expected to operate for two Earth weeks, or the length of one lunar day. Its onboard instruments were not designed to handle the extremely low temperatures of the subsequent 14 days of total darkness.

But its data will live on. Pragyan will relay its findings to the Vikram lander, which will also be conducting experiments until it too is killed by the lunar night. The lander is outfitted with cameras, a seismometer to measure “moonquakes,” a mini laser retroreflector that will help other spacecraft measure the distance to the moon with high precision, as well as instruments to measure the plasma density in the moon’s thin atmosphere. The lander will also have instruments capable of detecting isotopes like helium-3, a potential fuel for future fusion reactors.

The Vikram lander will relay all its data to the Chandrayaan-2 orbiter, which is expected to continue operating for at least a year. The orbiter, meanwhile, will be studying water ice at the lunar south pole and creating a 3D map of the lunar surface. Williams says this data will be “critical” to future human missions to the south pole.

The Chandrayaan-2 mission is a point of national pride for India. Unlike the Chandrayaan-1 mission, which contained several payloads from NASA and the European Space Agency, almost everything on the Chandrayaan-2 mission was made by the Indian Space Research Organization or Indian contractors. (The Russian space agency, Roscosmos, was initially developing the lunar lander, but after major delays the ISRO took it over in 2013 .) The only foreign payload is the laser reflector, which was supplied by NASA.

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