Two NASA astronauts made space history on Friday, completing the first spacewalk by an all-woman team when they stepped outside the International Space Station.
Christina Koch and Jessica Meir accomplished the much-anticipated milestone for NASA during a relatively routine mission to swap faulty batteries on the station's exterior.
"Mission accomplished!" NASA chief Jim Bridenstine tweeted on Friday. "Today’s historic achievement paves the way for our #Artemis program, which will send the first woman to the Moon in 2024."
"Ad Astra!" he added, Latin for "to the stars."
NASA aims to return to the moon with crewed missions by 2024 under the program dubbed Artemis, who in Greek mythology was the twin sister of Apollo, the name of the original moon program.
Koch and Meir, clad in white spacesuits and tethered by cords to the station some 408 kms above Earth, stepped into outer space at 7:38 a.m. Eastern time to replace a faulty power unit designed to help condition energy stored from the station's solar panels, NASA announced online as it showed live video of the action.
A first attempt at an all-female spacewalk in March was called off because one of the astronauts' medium-sized spacesuits was not configured and ready for the journey.
US President Donald Trump spoke with Koch and Meir by phone from the White House during the final stretch of the spacewalk. "Station, this is President Donald Trump. Do you hear me?"
The president, flanked by his daughter Ivanka Trump and vice president Mike Pence, said the astronauts were "brave, brilliant women" and mistakenly lauded the two as the first women to step outside the space station, prompting a gentle correction from Meir.
"We don't want to take too much credit, because there have been many other female space-walkers before us. This is just the first time that there have been two women outside at the same time," Meir, the 15th woman to conduct a spacewalk, responded.
Astronauts on the space station, which became operational in 2000, have tallied 221 maintenance spacewalks, 43 of which included women astronauts, according to NASA.
Friday's spacewalk, formally called extravehicular activities, is in line with the US space agency's aim to ramp up inclusivity in space.
Koch is set to complete the longest single space flight by a woman by remaining in orbit aboard the station until February 2020. She said gender milestones such as the spacewalk are significant.
"There are a lot of people who derive motivation from inspiring stories from people who look like them, and I think that it's an important aspect of the story to tell," she said at a NASA briefing in Houston this month.
Sandra Magnus, a former NASA astronaut who spent 136 days on the International Space Station, told Reuters she did not want events like Friday's spacewalk to become gimmicks.
"We want them to happen because people have the skill sets and they're available to do the job," said Magnus.
"On the other hand, it's important for young women to see women role models doing extraordinary things," she said. "So there's two sides of the coin. You want it to be normal but yet you want it to be special."