Nasa has asked for applications to go to the Moon.

It is the first time in four years the space agency has asked for new astronauts.

The opening of applications also comes as the company gears up to return to the Moon's surface for the first time in decades – and then use that as a step onto a trip to Mars.

US citizens can apply for the programme on the devoted federal website. Applications must be submitted before the end of the month.

The space agency has stressed that it is looking for people from "diverse backgrounds".

Nasa's groundbreaking decade of space exploration: In pictures Show all 10 1 /10 Nasa's groundbreaking decade of space exploration: In pictures Nasa's groundbreaking decade of space exploration: In pictures Mystic Mountain, a pillar of gas and dust standing at three-light-years tall, bursting with jets of gas from fledgling stars buried within, was captured by Nasa's Hubble Space Telescope in February 2010 Nasa/ESA/STScI Nasa's groundbreaking decade of space exploration: In pictures The first ever selfie taken on an alien planet, captured by Nasa's Curiosity Rover in the early days of its mission to explore Mars in 2012 Nasa/JPL-Caltech/MSSS Nasa's groundbreaking decade of space exploration: In pictures Death of a star: This image from Nasa's Chandra X-ray telescope shows the supernova of Tycho, a star in our Milky Way galaxy Nasa Nasa's groundbreaking decade of space exploration: In pictures Arrokoth, the most distant object ever explored, pictured here on 1 January 2019 by a camera on Nasa's New Horizons spaceraft at a distance of 4.1 billion miles from Earth Getty Nasa's groundbreaking decade of space exploration: In pictures An image of the Large Magellanic Cloud galaxy seen in infrared light by the Herschel Space Observatory in January 2012. Regions of space such as this are where new stars are born from a mixture of elements and cosmic dust Nasa Nasa's groundbreaking decade of space exploration: In pictures The first ever image of a black hole, captured by the Event Horizon telescope, as part of a global collaboration involving Nasa, and released on 10 April 2019. The image reveals the black hole at the centre of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides about 54 million light-years from Earth Getty Nasa's groundbreaking decade of space exploration: In pictures Pluto, as pictured by Nasa's New Horizons spacecraft as it flew over the dwarf planet for the first time ever in July 2015 Nasa/APL/SwRI Nasa's groundbreaking decade of space exploration: In pictures A coronal mass ejection as seen by the Chandra Observatory in 2019. This is the first time that Chandra has detected this phenomenon from a star other than the Sun Nasa Nasa's groundbreaking decade of space exploration: In pictures Dark, narrow, 100 meter-long streaks running downhill on the surface Mars were believed to be evidence of contemporary flowing water. It has since been suggested that they may instead be formed by flowing sand Nasa/JPL/University of Arizona Nasa's groundbreaking decade of space exploration: In pictures Morning Aurora: Nasa astronaut Scott Kelly captured this photograph of the green lights of the aurora from the International Space Station in October 2015 Nasa/Scott Kelly

“America is closer than any other time in history since the Apollo program to returning astronauts to the Moon. We will send the first woman and next man to the lunar South Pole by 2024, and we need more astronauts to follow suit on the Moon, and then Mars,” said NASA Administrator Jim Bridenstine in a statement.

“We’re looking for talented men and women from diverse backgrounds and every walk of life to join us in this new era of human exploration that begins with the Artemis program to the Moon. If you have always dreamed of being an astronaut, apply now.”

Any successful astronauts will be selected in 2021 and then begin training, a tough process that can take years.

Last time around, in 2015, some 18,300 people applied and just 11 new astronauts made it through to last year's graduation.

“Becoming an astronaut is no easy task, because being an astronaut is no easy task,” said Steve Koerner, NASA’s director of flight operations and chair of the Astronaut Selection Board at NASA’s Johnson Space Center in Houston.

“Those who apply will likely be competing against thousands who have dreamed of and worked toward going to space for as long as they can remember. But somewhere among those applicants are our next astronauts, and we look forward to meeting you.”

The requirements for applicants are strict: they must have a master's degree in a STEM field, or equivalent experience. They must also have two years of related professional experience or 1,000 hours of flying a jet aircraft.

To get through the selection programme, they will also have to pass a physical exam. For the first time, some of the assessment will take place online, with a test that will take up to two hours to complete.