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.