NASA has published photographs of the first flower grown on board the International Space Station as part of a two-year experiment to raise plants in space.
Although astronauts had grown lettuce and other vegetables in their space garden, this is the first time flowers - zinnias, in particular, which are edible - have bloomed outside earth's gravity.
US astronaut Scott Kelly hailed the achievement on Twitter with a photo of the orange blossom and a post saying "First flower ever grown in space makes its debut".
The flower-growing experiment began on November 16, when Kjell Lindgren activated the zinnia seeds, a process that proved more difficult than expected.
In December Kelly found the zinnia plants were not growing as fast as hoped and some of the plants developed a fungus due to the high humidity on board the ISS.
Nevertheless, Kelly managed to rejuvenate them.
Since mid-2014 the ISS has had a small "vegetable centre" to allow small-scale growing of plants for experiments.
The project is aimed at gathering information about plants' response to microgravity with an eye toward manned missions to Mars, which will require rationing water.
In an interview published on the weekend in the NASA blog, Alexandra Whitmire, a researcher with the agency, said plants would have great importance as longer space missions were mounted.
In 2012 astronaut Don Pettit grew zucchini, sunflowers and broccoli in plastic bags in a personal experiment.
The plants are grown aeroponically - without the need for soil - in an air or mist environment and the procedure requires much less water and fertiliser, with the plants growing three times faster than on earth.
