For the past year, astronaut Scott Kelly and cosmonaut Mikhail Kornienko have been on a mission in space, collecting research and capturing mesmerizing photos of the Earth. Tuesday, they will return to Earth, where their families, fans and extensive testing awaits them.

During the mission, Kelly - the first American to spend a year in space - captured several big weather events and even the Super Bowl. However, some of his photos also revealed how frail the Earth and its atmosphere has become.

“This past summer you could notice the drought in California clearly, and the fires,” Kelly . "Today we had this incredible pass over the Himalayas, and to just see all that pollution that’s just kind of riding up against those mountains from the south, it’s kind of heartbreaking to see that.”

According to ABC 13, , feeling the sunshine and smelling the rain when he returns to Earth. However, he will still miss the small, gravity-less craft he’s called home.

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“Leaving this amazing facility is going to be tough because I’ll probably never see it again, and I don’t expect I will,” said Kelly. “I’ve flown in space four times now, so it’s going to be hard in that respect, but I certainly look forward to going back to Earth. I’ve been up here for a really long time and sometimes, when I think about it, I feel like I’ve lived my whole life up here.”

One-year mission crew members Scott Kelly of NASA (left) and Mikhail Kornienko of Roscosmos (right) celebrated their 300th consecutive day in space on Jan. 21, 2016. By spending a total of 340 days aboard the International Space Station, the astronauts help scientists understand what happens to the human body while in microgravity for extreme lengths of time. Kelly is holding a zinnia grown in space as part of the Veggie experiment on the International Space Station.

(NASA)

The transition from zero gravity to the strength of Earth’s gravitational pull won’t be easy. Prolonged exposure to environments with reduced gravity , disturbance of sensory skills, difficulty maintaining balance, and a host of other problems, according to NASA.

Upon landing, the team will be retrieved from the Soyuz capsule and to see how their bodies changed while in space, NASA also reports. They will undergo fluid shifts, which deal with changes in the visual system, and field tests, which evaluate post-landing capabilities of the astronauts immediately after long space flights.

Data collected from this mission will also be used to help bolster two additional initiatives: the twins study and the journey to Mars.

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The will compare Kelly’s condition after a year in space with that of his twin brother, retired astronaut Mark Kelly, who is on Earth. This enables researchers to focus on an almost identical comparison of the brothers’ genetic make up, something never before recorded in human space research.

As for , information collected from this mission will help NASA create proper countermeasures for safeguarding future astronauts against the stresses of space on the human body.

“The mission will continue even after Scott returns,” said NASA Human Research Program chief scientist John Charles. “For the one-year mission research, we will be collecting post-flight medical data three-months and six-months after he is back on Earth. For the twins study research, we will continue to collect data as far out as a year after his return. The post-flight data are as important as the in-flight data to help us learn how to send humans safely to Mars and return them safely to Earth.”

Kelly and crews’ Tuesday journey on the re-entry capsule will make them appear as a streak across the sky, moving at 755 feet per second. As it re-enters the atmosphere, the capsule will begin to shed heat, losing two-thirds of its mass by the time it reaches 400,000 feet above the Earth. Just fifteen minutes before landing, four parachutes will open in an effort to slow it down, followed by a main chute that slows its descent just before landing. Two sets of three engines will fire to soften the landing just as it finally touches down.

The journey will take almost four hours.

MORE ON WEATHER.COM: Weather Events During Astronaut Scott Kelly's Year in Space

While on the One-Year Mission, astronaut Scott Kelly captured this photo of the Earth as Winter Storm Jonas was occurring.