Trump tweet raises questions about NASA plans for Moon mission

It was not immediately apparent what sparked the President's tweet about NASA's mission to the Moon - which back on May 13 was something Mr. Trump was proudly talking about.

"Under my Administration, we are restoring @NASA to greatness and we are going back to the Moon, then Mars," the President tweeted last month.

Here are the two tweets to compare:

NASA Administrator Jim Bridenstine has been talking for months about establishing a base on the Moon, using it as a stepping stone to prep for an eventual mission to Mars.

"President Donald Trump has asked NASA to accelerate our plans to return to the Moon and to land humans on the surface again by 2024," Bridenstine says in a quote that is featured on NASA's website about the Moon mission.

"This time, when we go to the Moon, we will stay," Bridenstine said. "And then we will use what we learn on the Moon to take the next giant leap - sending astronauts to Mars."

Just a few hours before the President's Friday tweet, the NASA chief was telling a Washington audience that the Trump Administration is committed to a new, lunar mission.

"The very first space policy directive of the President said, we're going to go back to the Moon," Bridenstine told an audience at the 38th International Space Development Conference.

In mid-May, President Trump officially asked Congress for $1.6 billion more to plan for a Moon mission - though the final cost would obviously be much more than that, something Democrats in Congress have questioned.

"We don’t know how much money will be required in total to meet the arbitrary 2024 Moon landing deadline or how that money will be spent," said Rep. Eddie Bernice Johnson (R-TX). "We don’t know how much additional money will subsequently be required to turn the crash program to get astronauts to the Moon by 2024 into a sustainable exploration program that will lead to Mars."