Donald Trump tweaks Obama-era order, to send astronauts to Moon, Mars

US President Donald Trump authorised the acting NASA administrator Robert M. Lightfoot Jr. to "lead an innovative space exploration programme to send American astronauts back to the moon, and eventually Mars" during a White House signing ceremony.

Standing with retired astronauts including Harrison Schmitt, one of the astronauts on Apollo 17 -- the last piloted mission to the moon, and Vice President Mike Pence, Trump on Monday touted the initiative as the first step in establishing a foundation on the moon for "an eventual mission to Mars and perhaps someday to many worlds beyond", reports CNN.

"The directive I am signing today will refocus America's space programme on human exploration and discovery.

"It marks an important step in returning American astronauts to the moon for the first time since 1972 for long-term exploration and use. This time we will not only plan on flag and leave our footprint."

The directive, which came on the 45th anniversary of Apollo 17's landing on the moon, called for collaboration with commercial companies and other nations, but it did not specify when the moon mission would occur or how much it might cost.

During a 2016 campaign event near NASA's Kennedy Space Centre in Florida, Trump had pledged to "free NASA from the restriction of serving primarily as a logistical agency for low Earth-orbit activities" and "instead refocus on space exploration", CNN reported.

"Under a Trump administration, Florida and America will lead the way into the stars," he said.

Pence, during the first meeting of the National Space Council in October, said the Trump administration "will return American astronauts to the moon, not only to leave behind footprints and flags, but to build the foundation we need to send Americans to Mars and beyond".

"The moon will be a stepping-stone, a training ground, a venue to strengthen our commercial and international partnerships as we refocus America's space program toward human space exploration."

Trump's announcement essentially revives goals that former President George W. Bush announced in 2004. The resulting NASA programme, Constellation, was to put astronauts on the moon by 2020 but was hobbled by delays and cost overruns, reports The New York Times.

Former President Barack Obama canceled it in 2010 and instead told NASA to focus on reaching an asteroid in the 2020s and then Mars in the 2030s.

The new heavy-lift rocket that NASA is developing for deep-space missions - known as the Space Launch System - could serve as a core component of a moon trip.

But the first uncrewed test of that rocket will not occur until 2019 or 2020, and the first flight carrying astronauts would follow only several years later.