"For all of the money we are spending, NASA should NOT be talking about going to the Moon - We did that 50 years ago," he wrote on Twitter as he jetted back to Washington from Ireland.

"They should be focused on the much bigger things we are doing, including Mars (of which the Moon is a part), Defense and Science!" Trump wrote.

There were several unclear aspects of the message, not least of which was Trump's description of Mars "of which the Moon is a part."

Earlier Friday, NASA Administrator Jim Bridenstine told an audience at the International Space Development Conference in Washington that "the very first space policy directive of the President said, 'We're going to go back to the moon.' "

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