Gerstenmaier started out as an engineer and eventually became the associate administrator for human exploration and operations in 2004.
In the email to NASA employees sent Wednesday evening, Bridenstine wrote: "As you know, NASA has been given a bold challenge to put the first woman and the next man on the Moon by 2024, with a focus on the ultimate goal of sending humans to Mars".
Effective suddenly, Bridenstine wrote in a letter to company workers, Ken Bowersox, a five-flight shuttle veteran, space station astronaut and Gerstenmaier's deputy, will take over on an acting basis while Gerstenmaier serves as "special advisor" to NASA Deputy Administrator Jim Morhard. He said that a new generation of leaders will step up and move out on the goal of returning astronauts to the moon. "In an effort to meet this problem, I've determined to make management changes to the Human Exploration and Operations (HEO) Mission Directorate".
Even 50 years later, the Apollo 11 mission that put a man on the moon for the first time still stands as one of the towering achievements of the human race.
Vice President Mike Pence announced in March that the Trump administration wished to speed up NASA's plans to reach the moon - launching the mission in 2024, instead of 2028.More news: This is the Mi A3, Xiaomi's new pure Android smartphone
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"The Trump Administration's ill-defined crash program to land astronauts on the Moon in 2024 was going to be challenging enough to achieve under the best of circumstances", Rep. Eddie Bernice Johnson of Texas said in a statement.
The high-profile executive changes at NASA came at a time when the space agency is working on the new moonshot program named Artemis. "Removing experienced engineering leadership from that effort and the rest of the nation's human spaceflight programs at such a crucial point in time seems misguided at best".
"What we need now is urgency", Pence said during a speech to a crowd at the US Space & Rocket Center in Huntsville, Alabama.
The Apollo Lunar Module Eagle set down on the Moon on July 20, the day when Neil Armstrong became the first person to step on alien soil.
The Washington Post earlier reported that many NASA employees were seemingly sceptical that the new Moon mission deadline is achievable without slashing other missions.