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A group that's looking for the first Red Planet colonists received applications from more than 200,000 prospective astronauts vying for a spot on a one-way trip to Mars.

The non-profit Mars One Foundation hopes to send teams of four spaceflyers on one-way Mars colony missions starting in 2023. Its initial 19-week application window closed on Aug. 31, with a final tally of 202,586 volunteers.

The only requirement to apply was to be over age 18. Those selected to move on to the next round will be notified by the end of this year. Over the next two years, a selection committee will narrow down that pool to up to 40 candidates, who will then begin seven years of astronaut training. A public vote will determine which four will be the first to go to Mars, never to return.

The applicant pool is quite diverse with more than 140 countries represented, Mars One said in a statement. Nearly a quarter of the aspiring Mars colonists are from the United States. Ten percent of the applicants are Indians, the second largest group in the pool.

Mars One, based in the Netherlands, will face some major technical and funding challenges in the years ahead. It has not yet picked a spacecraft or rocket for the long voyage. The project also estimated it will cost about $6 billion to send its first crew to the Red Planet and $4 billion for each of the following missions.

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The group started raising money through its application fees, which ranged from $5 to $75 depending on the applicant's country of origin. Mars One also hopes it will be able to raise funds with a reality TV show tracking the astronaut selection process and training.

Martian hopefuls who missed the deadline or were too young to apply this time around will have future chances to be considered. Mars One says it will start regular recruitment programs as the search for future Red Planet crews continues.