Two astronauts whose journey has resulted in some of the most jaw-dropping images in the solar system are set to return to Earth after spending almost an entire year in space.

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NASA’s Scott Kelly and Russian cosmonaut Mikhail Kornienko are due to land in Kazakstan at about 3.45pm AEST on Wednesday.

Sadly, it means there won’t be any more of Kelly’s mind-boggling photographic updates, like these below.

Health concerns

The men spent 340 days on the International Space Station. Typically, astronauts stay on the ISS for five or six months.

Returning home from nearly a year without gravity has its challenges and it is unknown how long it will take Kelly and Kornienko to recover from nearly 12 months at ‘microgravity’, since so few people have done it.

“Kelly has participated in a variety of research that will help scientists better understand how the human body reacts and adapts to long-duration spaceflight,” NASA said in a statement on Saturday.

“That knowledge will play a critical role in future NASA missions deeper into the solar system and on the Journey to Mars, in which a round-trip mission is likely to last 500 days or longer.”

Astronaut Chris Hadfield described the strange sensation of speaking in gravity as he had “learned to talk with a weightless tongue”.

“Right after I landed, I could feel the weight of my lips and tongue and I had to change how I was talking,” he said at a press conference when he returned from space in 2013.

Vision problems caused by a change in eyeball pressure, the inability to stand for long periods without fainting and calcium loss could be other health effects, according to a 2014 study, from NASA and the National Space Biomedical Research Institute.

But their mission wasn’t all about medical research.

Kelly posted regular updates of the stay to social media, capturing some breath-taking outer space images of Earth, from a vantage point few human beings have had the chance to see.

Day 304. That’s 4,864 orbits a’round’ our beautiful planet #Earth. #GoodNight from @space_station! #YearInSpace pic.twitter.com/tZZBbPcQ3q

— Scott Kelly (@StationCDRKelly) January 26, 2016

5K times around Earth can seem like #GroundhogDay but still a privilege. #GoodNight frm @space_station! #YearInSpace pic.twitter.com/3dUcWV6cXx

— Scott Kelly (@StationCDRKelly) February 3, 2016

The men also tried their hands at botany, growing the first ever flowers in space and tried the first batch of lettuce grown off Earth.

Yes, there are other life forms in space! #SpaceFlower #YearInSpace pic.twitter.com/BJFWvQXmBB — Scott Kelly (@StationCDRKelly) January 16, 2016

See more remarkable images below

#ColorsofEarth Red and purple Terra Australis. #YearInSpace pic.twitter.com/X8YNSsYFCI

— Scott Kelly (@StationCDRKelly) February 16, 2016

#ColorsofEarth Blue waters. #YearInSpace pic.twitter.com/4yWGdFLRKE

— Scott Kelly (@StationCDRKelly) February 16, 2016

Good afternoon #Egypt! Hope to see you up close some day. #YearInSpace pic.twitter.com/tNqye6i5gf

— Scott Kelly (@StationCDRKelly) February 11, 2016

Day 311. When you think of beautiful things. Don’t forget Earth. #GoodNight from @space_station! #YearInSpace pic.twitter.com/5jOGJbWNHy

— Scott Kelly (@StationCDRKelly) February 2, 2016

A splash of #EarthArt over the #Bahamas! #YearInSpace pic.twitter.com/sXPv1sojwR — Scott Kelly (@StationCDRKelly) January 19, 2016

#Countdown 2 days & a wake-up! Getting closer to Earth & hope Mars too. #GoodNight from @space_station! #YearInSpace pic.twitter.com/9x3ERJgAvc — Scott Kelly (@StationCDRKelly) February 28, 2016