Three Americans have cast their ballots from the most remote polling station in the solar system - the International Space Station, soaring 220 miles above Earth.

Navy Capt. Scott Kelly, U.S. Army Col. Douglas Wheelock and physicist Shannon Walker used a special secure line to the Johnson Space Center, which relayed the votes to the astronauts' respective home counties.

"It's an honor and a privilege to exercise our right as U.S. citizens to vote from the International Space Station," said Kelly, who voted on Sunday.