Astronauts on board the International Space Station (ISS) have tasted space-grown lettuce.

This image issued by Nasa TV on Monday shows (from left) Japan astronaut Kimiya Yui and Nasa astronauts Kjell Lindgren and Scott Kelly eating red romaine lettuce grown by the ISS team.

Astronauts have been growing crops in space for years for research, but this is the first time they have been allowed to eat their produce. It marks the start of the "veggie project" that will see more food grown in space.

Nasa scientists described the moment as another step towards enabling human missions to Mars.

The lettuce was grown in a special plant-growing box called Veg-01 (above), and was flown to space aboard the SpaceX Dragon cargo ship. The seeds are contained in rooting pillows, and were "activated" by Mr Kelly on July 8.