Hard to say who first woman will be to walk on the moon?

Fifty years after a military test pilot made the first striated boot prints in the thick gray powder of the lunar surface, NASA has an ambitious plan to send humans back to the moon by 2024.

But this time there’s a twist.

The next time a pair of astronauts set foot on the moon, the space agency has vowed that at least one of them will be a woman.

“I think most women would say it’s about time,” said former astronaut Janet Kavandi, director of NASA’S Glenn Research Center in Cleveland. “Women have been in the astronaut corps for decades now. We’ve gone everywhere else our male counterparts have gone.”

NASA is so serious about sending a woman to the moon that it has named its new lunar program Artemis. In Greek mythology, Artemis is the goddess of the moon and twin sister of the sun god Apollo.

“Having women astronauts on the moon is something that is long overdue,” said NASA administrator Jim Bridenstine. “And because we have this very diverse, highly qualified astronaut corps, we can make that a reality.”

Jeff Hoffman, another former astronaut who’s now a professor at MIT, said that sending a woman to walk on the moon would be deeply symbolic.

“When people ask when I knew I wanted to be an astronaut, I always say that like every other red-blooded boy, I was inspired by the men who flew on Apollo,” he said. “Unfortunately, the red-blooded girls didn’t have those role models.”

From 1969 to 1972, a total of 12 humans walked on the moon. All of them were American, white and male.

“It was a very homogenous group,” former astronaut and NASA administrator Charles Bolden said in a speech honoring the 50th anniversary of Apollo 11. NASA started recruiting astronauts in 1959, focusing first on military test pilots. All of them were men.

The first six women admitted to the astronaut corps joined in 1978. Among them was Sally Ride, who became the first American woman to fly in space in 1983.

Today, there are 12 women in NASA’S active astronaut corps, along with 26 men. If NASA keeps to its Artemis timeline, one of these women is likely to become the first female moonwalker.

When it comes time to select this woman, officials at the space agency will look for someone who is resilient, a good team player, in excellent physical shape and undaunted by risk. She must stay cool in the face of adversity and tackle unforeseen problems calmly and methodically. That doesn’t narrow the field much. “You could pick just about anybody in the office and they would be successful,” Kavandi said. “We have vetted them so much just to get in.” This history-making woman will probably have spent at least four to six months aboard the International Space Station, giving mission planners lots of data on how she performs in microgravity: Does she sleep well in space? Does she suffer from space sickness, an ailment that resembles motion sickness?

“Space affects everybody differently,” said Dorit Donoviel, director of the Translational Research Institute for Space Health at Baylor College of Medicine in Houston. “They are not going to send a complete rookie.”

In making the selection, the chief of the astronaut office also will consider how the astronauts perform during training, as well as the skills that are most needed for that first mission and who else will be along for the ride.

“You want to take into account the diversity of the crew,” Kavandi said. “You are not going to send two medical doctors or two military pilots.”

Hoffman has flown in space with both men and women. In his experience, men and women perform equally well.

“We have solid evidence that everyone can do the job,” Hoffman said. “We don’t change the job because of the sex of the astronaut. We change the shape of the urine collector.”

That’s not the only consideration. Anyone — male or female — who ventures beyond Earth’s protective magnetosphere is exposed to dangerous levels of space radiation that can damage cells and DNA. But studies have found that space radiation puts female astronauts at greater risk of dying from cancer compared with their male counterparts.

“This is a major concern,” Donoviel said. “The current permissible limits to time in space end up being twice as long for men than women.”

On the other hand, at least 17 male astronauts have developed a condition called spaceflight-associated neuro-ocular syndrome, or SANS. This is a swelling of the optic nerve that occurs when the lack of gravity causes fluids in the body to shift, allowing pressure to build up behind the eye. SANS can lead to vision loss — an ailment that could quickly derail a mission.

“We are not seeing it in women, and people don’t understand why,” Donoviel said.