After a five-week journey, the Indian Chandrayaan-3 spacecraft began its descent to the lunar surface. The craft flipped into a vertical landing position, paused to hover about 450 feet up, then alighted on a dusty plateau between two large craters.
“India is on the moon,” S. Somanath, the chairman of Indian Space Research Organization (ISRO), announced to a cheering crowd in mission control in Bengaluru on Wednesday, August 23.
After the Soviet Union, the United States, and China, India is the fourth nation to successfully land on the moon, and the first to visit the enigmatic south pole region.
“It’s absolutely wonderful to see our partners in India have a successful landing,” says David Kring, a planetary scientist at the Lunar and Planetary Institute in Houston, Texas. “It’s very challenging to put a spacecraft on the surface of another body.”
The difficulty of a moon landing has been underscored by a recent string of failures. Just days before the Chandrayaan-3 landing, Russia’s Luna-25 lander smashed into the surface after an engine failed to properly shut down. A lander built by the Japanese company Ispace—carrying a rover built by the United Arab Emirates—ended catastrophically in April after the spacecraft misjudged its altitude and ran out of fuel. India’s first craft to attempt a moon landing in September 2019 also crashed.
“From the day we started rebuilding our spacecraft after [the] Chandrayaan-2 experience, it has been breathe in, breathe out, Chandrayaan-3 for our team,” said Kalpana Kalahasti, the associate project director of the mission, after the craft touched down.
That team had more reason to celebrate the next morning in India when a small rover named Pragyaan “ramped down from the lander and India took a walk on the moon!” ISRO reported.
The rover, whose name means “wisdom” in Sanskrit, and the lander Vikram, named for the Indian scientist Vikram Sarabhai who helped establish ISRO, will take scientific measurements for about two weeks. After that time, the area will plunge into a two-week long lunar night that the two spacecraft are not expected to survive since they run on solar power.
Before long, however, a new wave of robots could join the Pragyaan rover and Vikram lander on the moon. A Japanese lander called SLIM, or the Smart Lander for Investigating Moon, is slated to launch Saturday, August 26, hitching a ride with a new space telescope, both developed by the Japan Aerospace Exploration Agency (JAXA).
Other major missions, such as NASA’s VIPER rover and China’s Chang’e 6 sample return, are expected to launch in 2024, poised to reveal new parts of the moon ahead of the Artemis III mission to return humans to the surface.
“It is a very exciting era,” Kring says. “It’s going to be fun.”
Dialing in the landing
Chandrayaan-3 landed at about 69 degrees south latitude, closer to the lunar south pole than any craft before it. On Earth, this would be roughly equivalent to the outer coasts of Antarctica, though it is still “a long way from the pole at 90 degrees,” Kring says.
“They are in this near-polar terrain, which is very old,” he says. “It’s far more ancient than any of the Apollo landing sites, and … geologic studies of that terrain are very exciting.”
The rover will analyze the mineral composition of the area, while the lander will use a seismometer to listen for “moonquakes”—which can occur as the moon slowly cools and contracts—as well as measure temperatures and atmospheric conditions.
But when the sun sets on Chandrayaan-3, the rover and lander are expected to go dark forever. They have already accomplished their most important goal: safely landing and deploying. Future missions will carry on the exploration of the lunar surface—India could return in a few years during a proposed joint mission with Japan.
JAXA may not have to wait that long, though, as its SLIM lander could launch this week. The eight-foot-tall craft will orbit the moon before attempting a pinpoint landing using image recognition technology to identify craters and precisely determine its location. During the final descent, a sophisticated radar will help the spacecraft land within 100 meters of its target. By contrast, the Chandrayaan-3 landing zone was an ellipse about four kilometers wide.
This type of precision landing will be needed in the future to explore the deep craters and rugged slopes of the lunar south pole. This jagged landscape has areas that never see sunlight, where scientists believe deposits of water ice may have accumulated—a vital resource for establishing a human outpost on the moon.
“The south pole is an incredible, incredible world. It’s topography is extreme, with these really large craters, very tall mountains,” says Anthony Colaprete, the project scientist for the VIPER mission at NASA's Ames Research Center in California. “It is really a fascinating landscape.”
Searching for resources
The craters at the moon’s south pole have entranced scientists for decades. They include some of the oldest and largest lunar craters and hold clues about the state of the solar system more than 3.5 billion years ago, when both the moon and Earth were being pummeled by asteroids.
On much of the moon, one cycle of day and night lasts about 28 Earth days. At the south pole, however, the sun never sets, and instead circles slowly around the horizon. This casts perpetual shadows on some parts of the craters.
These pockets of darkness, among the coldest places in the solar system, may contain deposits of substances that scientists call volatiles—compounds that would sublimate to gas in the sunlight. The most tantalizing volatile on the moon is H2O.
“If water ice is present in quantities and in a distributed state that is recoverable, that would be valuable,” Kring says. “Water, first of all, is useful as an astronaut consumable. It’s useful because it’s a very effective shield against space radiation. And third, you can separate the hydrogen and the oxygen for rocket propellant.”
To investigate whether this ice is accessible to future crewed missions, NASA is preparing to launch a rover called VIPER, or the Volatiles Investigating Polar Exploration Rover, to the moon as soon as November 2024. Equipped with a meter-long drill, the golf-cart-size rover will explore the craters atop an expansive mountain called Mons Mouton near the moon’s south pole.
"Inside these ancient craters are permanently shadowed regions that haven’t seen the light of day in billions of years,” Colaprete says. During its 100-day mission, VIPER will venture into the craters’ shadowy realms, where temperatures can near absolute zero.
Once scientists know where the ice is, and how much, accessing it will require sending water harvesting equipment to the lunar surface. To prepare, NASA has funded multiple aerospace companies to develop lunar landers that could take not only science instruments, but eventually tools and supplies to help construct a base. Two of those spacecraft—the Nova-C lander built by Houston-based Intuitive Machines, and the Peregrine lander from Pittsburgh-based Astrobotic Technology—could launch later this year.
Private companies in India, Japan, Israel, and elsewhere also have their sites set on the moon, with a whole fleet of designs that could one day help shuttle cargo to astronauts living in a habitat on the surface.
To get humans back to the moon, NASA is ramping up its Artemis program. Artemis I, the first test launch of the giant Space Launch System rocket that will carry people to the moon, blasted off on November 15, 2022. Now the space agency is preparing for Artemis II, scheduled to fly astronauts around the moon and back in November 2024. Then Artemis III is slated to land a crew on the surface as soon as December 2025.
But to pull off a crewed landing in that timeframe, NASA is relying on SpaceX’s Starship rocket. The giant launch vehicle, the biggest and most powerful ever flown, broke apart in a fiery explosion during its first test launch in April. It also partially destroyed the launch pad, flinging concrete and metal debris for thousands of feet.
NASA plans to use a modified version of the upper stage of this rocket to land people on the moon, and Artemis III cannot proceed as planned without it. Elon Musk, SpaceX’s founder, discussed upgrades to Starship and its launch pad during an online interview with Bloomberg in June, when he estimated about a 60 percent chance of reaching orbit in the next attempt.
“There’s a lot of still unknowns about what Starship is exactly going to look like when it’s done for lunar missions,” says Jason Davis, a senior editor at the Planetary Society. “How long can we stay there on the moon inside that thing? How much cargo can it bring?”
NASA has also contracted Jeff Bezos’ rocket company Blue Origin to lead a consortium of aerospace companies in building a second crewed lunar lander. Meanwhile, China plans to land astronauts by 2030 and is gearing up for the Chang’e 6 sample-return mission to the lunar south pole next year.
Until crewed lunar landers can be completed, the moon’s surface will need to be studied from afar using robotic explorers like Chandrayaan-3. But perhaps in the not-too-distant future, scientists and engineers in space suits will visit the shadowed craters of the lunar south pole to harvest their ice and discover their secrets.