ORLANDO, Fla., Jan. 20 (UPI) -- NASA Administrator Jim Bridenstine stepped down as planned Wednesday and posted a message on Twitter to thank employees and all who supported his tenure at the space agency.
Bridenstine, who left on the day of President Joe Biden's inauguration, made a public plea for continued support of NASA and planned missions to the moon and Mars.
He referenced historic disagreements at the agency and in Washington over whether to support another moon mission or a Mars mission, or simply to focus on Earth sciences.
"It's not about the moon or Mars, which put us in conflict in the House of Representatives between Republicans and Democrats. It's about both," Bridenstine said.
"It's about going to the moon to get the science and discovery that we need to learn how to live and work in another world for long periods of time."
NASA associate administrator Steve Jurczyk has become acting administrator. Ellen Stofan, a former NASA chief scientist, has overseen President Joe Biden's transition team for NASA and space policy.
Stofan is considered a potential candidate for NASA administrator, and if appointed to that job, would become the first woman to lead the space agency.
"I'll tell you when a new team comes in, give them all your support because they need it," Bridenstine said in his recorded message. "They deserve it. ... They'll have all my support and I hope they have all your support."
Bridenstine oversaw a heady three years at NASA that included the continuing construction of a new Space Launch System moon rocket, the launch of the Mars rover Perseverance and the return of NASA crewed spaceflight to U.S. soil after a nine-year absence.
That gap ended in May, when NASA's Commercial Crew Program launched astronauts from Florida to the International Space Station in a SpaceX capsule aboard a SpaceX rocket.
In 2017, then-President Donald Trump nominated Bridenstine, a former U.S. representative from Oklahoma, to head NASA.
Congress approved the appointment in a party-line vote in 2018, with some Democrats objecting because Bridenstine was the first NASA administrator who had no formal background as a space or science professional.
NASA's women astronauts -- at least one likely to walk on moon
Jasmin Moghbeli
Moghbeli poses for a portrait in the Systems Engineering Simulator for the International Space Station and advanced spaceflight programs at the Johnson Space Center on July 9, 2019. She will train for the moon mission. Photo by Bill Ingalls/NASA
Jessica Watkins
Watkins is helped into a spacesuit before underwater spacewalk training at Johnson Space Center on May 22, 2019. She will train for the moon mission. Photo by David DeHoyos/NASA
Kayla Barron
Barron dons her spacesuit in Houston on July 12, 2019. She will train for the moon mission. Photo by Bill Ingalls/UPI
Kate Rubins
Rubins prepares for a spacewalk on board the International Space Station on August 10, 2016. She will train for the moon mission. Photo courtesy of NASA
Christina Koch
Koch collects and packs Mizuna mustard greens grown and harvested inside the International Space Station's veggie botany facility on November 13, 2019. She will train for the moon mission. Photo courtesy of NASA
Anne McClain
Expedition 59 astronaut McClain is helped out of the Soyuz MS-11 spacecraft just minutes after she landed in a remote area near the town of Zhezkazgan, Kazakhstan, on June 25, 2019. She will train for the moon mission. Photo by Bill Ingalls/NASA
Stephanie Wilson
Wilson poses for a portrait at Johnson Space Center on July 11, 2019. She will train for the moon mission. Photo by Bill Ingalls/NASA
Jessica Meir
Meir sits for her portrait in an Extravehicular Mobility Unit, the suit used for spacewalks, on September 11, 2018. She will train for the moon mission. Photo by Josh Valcarcel/NASA
Nicole Aunapu Mann
Nicole Aunapu Mann attends the announcement that she was being assigned to the Boeing CST-100 Starliner Crew test flight to the International Space Station on August 3, 2018. Photo Bill Ingalls/NASA
Tracy Caldwell Dyson
Dyson pauses for a portrait in her spacesuit before going underwater in the Neutral Buoyancy Lab at NASA's Johnson Space Center in Houston on July 8, 2019. Photo by Bill Ingalls/UPI
Loral O'Hara
O'Hara stands in front of a T-38 trainer aircraft at Ellington Field near Johnson Space Center on June 6, 2017. Photo by Robert Markowitz/NASA
Zena Cardman
Cardman awaits the next steps from instructors during water survival training in Houston on August 23, 2017. Photo by David DeHoyos/NASA
Sunita Williams
Expedition 32 flight engineer and Expedition 33 commander Williams participates in spacesuit fit check at the Johnson Space Center on September 8, 2011. Photo courtesy of NASA
Jeanette Epps
Epps sits for her portrait on September 30, 2009. Photo by Robert Markowitz/NASA
Megan McArthur
McArthur poses for a portrait on the Crew Access Arm of the mobile launcher at Kennedy Space Center in Florida on June 25, 2019. Photo by Joel Kowsky/NASA
Shannon Walker
Walker welcomes viewers at the Johnson Space Center to watch the live coverage of Expedition 40/41 launch as it unfolds at Baikonur, Kazakhstan, on May 28, 2014. Members of the crew can be seen on the nearby screen. Photo courtesy of NASA
