NASA on Tuesday introduced the four astronauts it will send to space on the Artemis III mission, which will demonstrate the flight and docking capabilities of an as-yet-untested lunar lander. But on Wednesday, NASA Administrator Jared Isaacman defended the decision not to include any women on the crew.

"I have seen reactions ranging from disappointment to outrage," Isaacman wrote in a post on social media network Threads. "The Astronaut Office assigns the crew that gives the mission the best chance of meeting its objectives, taking into account many factors, including the background and expertise of the astronauts, such as test pilot experience, development work on specific programs and availability." 

He added that people making these criticisms "may not be aware" of women who have already been chosen to launch to the International Space Station in the meantime and aren't available for Artemis III or "those who have been undergoing lunar-specific training that would be a better fit for a future surface mission," presumably referring to the Artemis IV mission.

The announcement came two months after the Artemis II mission sent four astronauts -- including one woman -- arcing around the moon for the first time since the moon landing missions of the early 1970s.

The Artemis III crew, scheduled to launch in 2027, will be NASA astronauts Randy Bresnik (commander), Andre Douglas and Frank Rubio (mission specialists) and the Italian Space Agency's Luca Parmitano (pilot).

Three of them are seasoned spacefarers. Bresnik has made two trips to space, starting with a space shuttle mission in 2009. Parmitano has also traveled to space twice, for a total of 367 days. Rubio, who managed a coolant leak crisis during a mission, spent 371 continuous days in space, setting a record for NASA astronauts. Douglas will be making his first spaceflight.

The newly announced members of the program were joined on stage Tuesday by three of the four Artemis II astronauts: Reid Wiseman, Victor Glover and Christina Koch. That crew spent 10 days in space, making a single pass around the far side of the moon, traveling farther from Earth than any other humans in history and capturing breathtaking images before splashing down safely in the Pacific Ocean.

The Artemis III mission won't be going all the way to the moon. Instead, it will remain in low Earth orbit to test how NASA's Orion spacecraft docks with a private-sector-built lunar lander, one of which is supplied by the Jeff Bezos-owned aerospace company Blue Origin. But Blue Origin late last month suffered a catastrophic setback when one of its New Glenn rockets detonated in a massive explosion, damaging the company's only launchpad.

John Couluris, lunar senior vice president at Blue Origin, said during the Tuesday livestream that the explosion represented a "significant anomaly" for the company.  

NASA and Blue Origin officials were tight-lipped about the timing of the repairs, but remained committed to the existing mission timeline. Tuesday's announcement reiterated the timetable for the Artemis program, which aims to put humans on the surface of the moon again, some two years from now.

"We're going to return to the moon before the end of 2028," Isaacman said on the livestream.

The space agency is also planning to use a lander from Elon Musk's SpaceX for its Artemis missions. A modified version of the company's Starship rocket, which has yet to travel to space, will dock with NASA's Orion spacecraft before being used to touch down on the lunar surface.  

The lunar landings will be a step in a larger initiative to use the moon as a staging ground for journeys to Mars. NASA plans to start building a moon base during its Artemis V mission.

Representatives for NASA, Blue Origin and SpaceX did not immediately respond to a request for additional comment.