Former NASA astronaut José Hernández said Monday that travel to Mars is “a good 15 years away.”

“As I’ve always said … space travel is not trivial, and so what we need to do next is, we’re going to retire the International Space Station, invest that — that operational money in developing a lunar base where technologies that are needed to go to Mars need to be developed and tested and proved, because right now, there’s too many technical hurdles,” Hernández told NewsNation’s Blake Burman on “The Hill.”

“We’re a good 15 years away from going to Mars, not five years as Elon Musk alludes to,” he added.

Hernández’s comments come a day before astronauts Butch Wilmore and Suni Williams are set to come to Earth following a stay of nine months at the International Space Station. On Sunday, NASA said that it met with tech billionaire Elon Musk’s spacecraft company SpaceX to “assess weather and splashdown conditions” off Florida’s coast and was aiming for later Tuesday “based on favorable conditions.”

“The updated return target continues to allow the space station crew members time to complete handover duties while providing operational flexibility ahead of less favorable weather conditions expected for later in the week,” NASA said, per a press release.

Back in January, Trump said that he had “asked Elon Musk and @SpaceX to ‘go get’ the 2 brave astronauts who have been virtually abandoned in space.”

“I have just asked Elon Musk and @SpaceX to ‘go get’ the 2 brave astronauts who have been virtually abandoned in space by the Biden Administration,” Trump wrote in a previous Truth Social post. “They have been waiting for many months on @Space Station. Elon will soon be on his way. Hopefully, all will be safe. Good luck Elon!!!”

The Hill has reached out to NASA and the White House for comment.