Scott Kelly has officially returned to Earth after one year in space. While staying a year in space is a feat in and of itself, what really have scientists excited are the implications for the mission to Mars.

Kelly is scheduled to return to Houston about 24 hours after landing back to Earth in Kazakhstan, at about 11:45 p.m. EST on Wednesday. That's after a mission that's lasted twice as long as a typical mission, or about 340 days.

While many experiments were conducted while Kelly was in space, the main one was to see the effects of space on the human body. This is critically important when it comes to understanding the effects of long-duration spaceflight, such as the eventual mission to Mars.

The science to actually driving the one-year mission occurred a year before Kelly headed to the space station. NASA scientists collected biological samples from Kelly, and also performed assessments to establish baselines. Comparison samples were taken throughout Kelly's stay in space, and will continue for a year or more after his return to Earth.

What really makes this study so interesting, though, is that Scott Kelly has an identical twin brother, former astronaut Mark Kelly. While Scott was in space, Mark participated in parallel twin studies on Earth in order to provide scientists with more bases for comparisons.

NASA is currently pushing to send a human to Mars. However, there are many hazards that humans must face within the depths of space. There's low-level radiation that could have an impact over time. In addition, the weightlessness of space also has an effect on muscles and even eyesight. This means that NASA scientists are eager to conduct studies and figure out a way to counteract these effects during a long-term mission.

The current plan for the mission to Mars involves several stages. Currently, NASA is looking at how space affects the body in order to protect astronaut health. The next stage, though, is deep space. NASA will send a robotic mission to capture and redirect an asteroid to orbit a moon. Astronauts aboard the Orion spacecraft will then explore the asteroid in the 2020s and return to Earth with samples. This experience will help NASA test new systems and capabilities for even longer term space missions.

For now, though, Scott Kelly represents an important step when it comes to sending astronauts to the Red Planet.