Donald Trump's plans for his 2nd term are out of this world ... with the returning commander-in-chief announcing a new Mars mission during his inaugural address.

Check it out ... while addressing the nation inside the U.S. Capitol Building Monday, Trump declares his goal to plant a U.S. flag on the 4th planet from the Sun ... in order to be seen as "a growing nation" again.

He adds ... "We will pursue our manifest destiny into the stars, launching American astronauts to plant the Stars and Stripes on the planet Mars."

Trump's declaration received an enthusiastic response from the crowd in the Capitol Rotunda ... especially from Elon Musk -- the new co-lead for the Department of Government Efficiency -- who put up 2 thumbs up and gave an enthusiastic smile at the proclamation.

If Trump's Mars mission comes to fruition, it will be an historic one for space travel ... given only robotic landers and rovers have touched down on Mars.

It appears Trump is looking to have his own John F. Kennedy moment in his 2nd term ... as JFK famously advocated to send astronauts to the moon during his presidency.

The 35th POTUS never got to see his dream realized, however ... he was assassinated in 1963, more than 5 years before Neil Armstrong made one giant leap for mankind.

Nonetheless, we're still trying to get 2 astronauts stuck in space home ... so, let's maybe wait and see if this Mars mission actually happens.