Washington: Astronauts Jessica Meir and Christa Koch made history with the first all-female spacewalk, an excursion to repair a power unit on the International Space Station.
The mission began at 11.39 GMT on Friday and the women spent seven hours and 17 minutes working outside the ISS as it circled the Earth at 27,600 km/h (17,100 mph), Efe news reported.
Viewers who tuned into NASA's live-stream of the spacewalk saw the white-suited astronauts in stark relief against the black of deep space.
Koch and Meir paused in their labors for a few minutes to take a call from US President Donald Trump.
"Station - this is President Donald Trump do you hear me?," he began. When the astronauts answered - after a long pause - he responded: "I was starting to get worried about you. You're in an interesting place."
Describing Meir and Koch as "brave, brilliant women," Trump hailed their "historic" mission.
"You're doing an incredible job," he told the astronauts. "This is a first step, because we're going to the moon, and then we're going to Mars."
Trump was joined for the call by Vice President Mike Pence, NASA Administrator Jim Bridenstine and Ivanka Trump, the president's daughter and adviser.
"For us, it's just coming out here and doing our job today," Meir said. "At the same time, we recognize that it is a historic achievement and we do of course want to give credit to all those that came before us.
"There have been a long line of female scientists, explorers, engineers and astronauts, and we have followed in their footsteps to get us where we are today," the 42-year-old biologist said.
The first woman to walk in space was Russia's Svetlana Savitskaya, who accompanied fellow cosmonaut Vladimir Dzhanibekov on an excursion outside their spacecraft in 1984.
Later that same year, Kathryn D. Sullivan became the first American woman to perform a spacewalk.
"The first all-woman spacewalk is a milestone worth noting and celebrating as the agency looks forward to putting the first woman and next man on the Moon by 2024 with NASA's Artemis lunar exploration program," the US space agency said in a statement.
NASA acknowledged that the Koch-Meir mission was attracting a lot more interest than is usually the case with spacewalks.
Koch, an engineer, arrived at the ISS on March 14 and is on her way to setting a new record for the longest period spent in space by a woman, as her mission is scheduled to last 328 days.
The current record, 288 days, was set by American astronaut Peggy Whitson.
"In the end, I do think it's important, and I think it's important because of the historical nature of what we're doing. In the past women haven't always been at the table," Koch, 40, said in an interview shared by NASA.
"It's wonderful to be contributing to the space program at a time when all contributions are being accepted when everyone has a role. That can lead in turn to increased chance for success," she said.
"There are a lot of people who derive motivation from inspiring stories of people who look like them, and I think it's an important story to tell," the astronaut added.
The all-woman spacewalk was originally scheduled to take place in March with Koch and astronaut Anne McClain.
But McClain was replaced at the last minute by astronaut Nick Hague at the last minute due to an with the sizes of the available spacesuits.