US astronaut Christina Koch, who led the first all-female spacewalk in 2019, has returned to Earth after a record stay aboard the International Space Station.

Key points: Astronaut Christina Koch has broken two records, first as a member of the first all-female spacewalk and now for the longest continuous stay in space by a woman

Astronaut Christina Koch has broken two records, first as a member of the first all-female spacewalk and now for the longest continuous stay in space by a woman Her lengthy mission will provide NASA with much-needed data on how the weightlessness of gravity and space radiation affects the female body

Her lengthy mission will provide NASA with much-needed data on how the weightlessness of gravity and space radiation affects the female body The science could prove useful for the US space agency's aim of building a permanent station on the moon's surface within the next decade

Ms Koch, 41, landed in Kazakhstan on Thursday (local time), ending a 328-day mission expected to yield new insights into deep-space travel.

"I'm just so overwhelmed and happy right now," Ms Koch said, sitting in a chair wrapped in blankets as she waited to be carried into a medical tent to restore her balance in gravity.

The Soyuz MS-13 capsule touched down on the Kazakh desert steppe at 8:12pm AEDT carrying Ms Koch, European astronaut Luca Parmitano and Russian cosmonaut Alexander Skvortsov.

Her mission broke the record for the longest continuous stay in space by a woman, previously held by NASA's Peggy Whitson.

Jessica Meir (L) and Christina Koch performed a spacewalk to replace a broken battery charger in October 2019. ( AP: NASA )

She also achieved a gender milestone in a relatively routine spacewalk with fellow NASA astronaut Jessica Meir last October, that marked the first time two women stepped out of the space station at the same time.

NASA's first attempt for an all-female spacewalk in March 2019 was called off because one of the astronauts' medium-sized spacesuits was not properly configured in advance, igniting a gender-equity debate within the space community.

The space capsule descends above Kazakhstan. ( AP: Sergei Ilnitsky )

Astronauts on the space station, whose 20th anniversary in low-Earth orbit comes later this year, have tallied 227 maintenance spacewalks, nearly two dozen of which included women astronauts, according to NASA.

Ms Koch set a record for the longest spaceflight by a woman on the International Space Station. ( AP: Sergei Ilnitsky )

Ms Koch and Ms Meir conducted two more spacewalks together in January.

NASA said Ms Koch's lengthy mission would provide researchers with much-needed data on how the weightlessness of gravity and space radiation affected the female body on long-duration spaceflights.

That science, to be studied in the coming months, could prove useful for the US space agency's aim of building a permanent station on the moon's surface within the next decade.

US astronaut Scott Kelly's 340 days in orbit starting in 2015 demonstrated that long-term spaceflight caused human health effects such as thickening of the carotid artery and retina, changes in gene expression and slight cognitive impairments for men.

Ms Meir and Ms Koch working on the side of the International Space Station. ( Twitter: International Space Station )

Launched into orbit last March, Ms Koch's mission was extended in April from its original span of six months to nearly a year after she was already aboard the station.

Ms Koch and Ms Meir made history in conducting the first all-female spacewalk in October 2019. ( Twitter: @NASA )

Reuters