Why NASA Is Going Back to the Moon

“We are going.”

That is the catch phrase that NASA is using in the lead-up to the debut flight of its new moon rocket, which could launch as early as Monday at 8:33 a.m. Eastern time. It is a phrase repeated by agency officials, added as a hashtag on social media postings and proclaimed on banners hung around the launch site at the Kennedy Space Center in Florida.

If you are not a space buff, sending astronauts back to the moon might seem like a big yawn.

Why? We already went.

Why should NASA repeat what it did half a century ago, especially since astronauts will not actually step on the moon for several years, and by that time, NASA will have spent about $100 billion?

NASA officials today argue that the moon missions are central to its human spaceflight program and not simply a do-over of the Apollo moon landings from 1969 to 1972.

“It’s a future where NASA will land the first woman and the first person of color on the moon,” Bill Nelson, the NASA administrator, said during a news conference this month. “And on these increasingly complex missions, astronauts will live and work in deep space and will develop the science and technology to send the first humans to Mars.”

That’s a change from as recent as 2010, when President Barack Obama delivered a speech at the site where Americans launched to the moon and said NASA should aim for more ambitious destinations like asteroids and Mars and move beyond the moon.

“We’ve been there before,” Mr. Obama said.

Today’s program was named Artemis by NASA leaders during the Trump administration. In Greek mythology, Artemis was the twin sister of Apollo. The program’s first step will be the upcoming test flight of the moon rocket, known as the Space Launch System, with the Orion capsule on top where astronauts will sit during future missions. This uncrewed flight, where Orion will swing around the moon before returning to Earth, is to wring out any issues with the spacecraft before putting people on board.

In case any weather or technical issues prevent the rocket from getting off the ground on Monday, it can try again on Friday or the following Monday. Weather forecasters on Saturday predicted a 70 percent chance of favorable conditions for the launch.

In addition to the mission’s function as a proving ground for technologies needed for a much longer trip to Mars, NASA is also hoping to jump-start companies looking to set up a steady business of flying scientific instruments and other payloads to the moon, and to inspire students to enter science and engineering fields.

“We explore because that’s part of our nature,” Mr. Nelson said in an interview.

It’s not just NASA that wants to go to the moon these days. In recent years, China has successfully landed three robotic missions on the moon. India and an Israeli nonprofit also sent landers in 2019, although both crashed. A South Korean orbiter is on its way.

Mr. Nelson said that China’s expanding space ambitions, which include a lunar base in the 2030s, also provided motivation for Artemis. “We have to be concerned that they would say: ‘This is our exclusive zone. You stay out,’” he said. “So, yes, that’s one of the things that we look at.”

For scientists, the renewed focus on the moon promises a bonanza of new data in the coming years.

The rocks collected by the astronauts during the Apollo missions upended planetary scientists’ understanding of the solar system. Analysis of radioactive isotopes provided precise dating of various regions of the moon’s surface. The rocks also revealed a startling origin story for the moon: It appears to have formed out of debris ejected into space when a Mars-size object slammed into Earth 4.5 billion years ago.

But for two decades after Apollo 17, the last moon landing, NASA turned its attention away from the moon, which to many appeared to be a desolate, dry, airless world. It shifted its focus to other places in the solar system, like Mars and the multitude of moons of Jupiter and Saturn.

Scientific interest in the moon never fully disappeared, though. Indeed, its desolate nature means that rocks that hardened billions of years ago remain in almost pristine condition.

“As scientists, we understand that the moon is in some sense a Rosetta Stone,” said David A. Kring of the Lunar and Planetary Institute near Houston. “It is the best place in the solar system to study the origin and evolution of planets in the solar system.”

Scientists also discovered that the moon is not as dry as they had thought.

Water, frozen at the bottom of eternally dark craters at the poles, is a valuable resource. It can provide drinking water for future astronauts visiting the moon, and water can be broken down into hydrogen and oxygen.

The oxygen could provide breathable air; oxygen and hydrogen could also be used as rocket propellant. Thus, the moon, or a refueling station in orbit around the moon, could serve as a stop for spacecraft to refill their tanks before heading out into the solar system.

The ices, if they were ancient accumulations over several billion years, could even provide a scientific history book of the solar system.

Growing knowledge of the ices drew renewed interest in the moon. In the early 2000s, Anthony Colaprete, a planetary scientist at the NASA Ames Research Center in Mountain View, Calif., said he thought about the moon “only in passing.”

Then NASA put in a call for proposals for a spacecraft that could tag along to the moon with the upcoming Lunar Reconnaissance Orbiter mission. Dr. Colaprete, who at the time was primarily involved with climate models of Mars, proposed the Lunar Crater Observation and Sensing Satellite, or LCROSS, which he thought could confirm hints of water ice that had been detected by a couple of lunar spacecraft in the 1990s.

LCROSS would direct the upper stage of the rocket that launched the mission into one of the polar craters at 5,600 miles per hour and then a small trailing spacecraft would measure what was kicked up by the impact.

“It was a rather crude sampling method,” Dr. Colaprete said in an interview.

But NASA liked the idea and selected it. In June 2009, the rocket carrying the Lunar Reconnaissance Orbiter and LCROSS launched. That October, LCROSS made its death dive into Cabeus crater, near the moon’s south pole.

A month later, Dr. Colaprete had his answer: There was indeed water at the bottom of Cabeus, and quite a bit of it.

Instruments on an Indian orbiter, Chandrayaan-1, also found unmistakable signs of water, and scientists using state-of-the-art techniques found water locked up in the minerals of old Apollo 15 and Apollo 17 rocks.

But Barbara Cohen, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., said scientists had many unanswered questions.

There are cold regions with ice, but also cold regions that appear to be ice free. Some places are frosty at the surface and others have ice below the surface, but the two regions do not always overlap. “We don’t fully understand when or how that water got there,” she said.

That means scientists also do not really know how much water is there or how easy it will be to extract the water from the surrounding rock and soil.

Dr. Colaprete is still working on the moon, too. “The community has grownin the last two decades,” he said. He is now the principal investigator for the Volatiles Investigating Polar Exploration Rover, or VIPER, a robotic vehicle that is to land near the south pole in late 2024 and venture into some of the dark craters to get a close-up look, including drilling a meter into the ground.

“One of our primary goals is to understand the origin and forms of water on the moon,” Dr. Colaprete said.