NASA astronauts Peggy Whitson and Jack Fischer are pictured packing up gear inside the International Space Station on June 3, 2017. Photo: NASA

NASA astronauts Peggy Whitson and Jack Fischer returned to Earth on Sept. 2 after spending months on the International Space Station as part of Expedition 50/51 and Expedition 51/52.

Whitson’s return home marked her completion of three long-duration missions to the ISS. She now holds multiple records – including most time accumulated on spacewalks, and longest time spent in orbit by a female astronaut – among others.

Expedition 51/52 was Fischer’s first opportunity to travel to the ISS, and he joined Whitson in April.

Whitson launched to the ISS on Nov. 17, 2016, spending more than nine months in space. She had already completed two six-month tours of duty aboard the station – the first in 2002 as part of the Expedition 5 crew, followed by Expedition 16 in 2008 as the station commander.

Whitson was initially scheduled to return to Earth from the latest mission in June, but her time was extended an additional few months. Whitson now holds the U.S. record for cumulative time in space, with 665 days in orbit. She has also spent the longest time in orbit during a single spaceflight than any other female astronaut at 288 days, according to NASA. Additionally, Whitson earned recognition for most spacewalks and time spent spacewalking by a female astronaut. She now has 10 spacewalks under her belt, accumulating to 60 hours and 21 minutes.

Fischer joined Whitson on April 20, 2017 and spent a total of 136 days in orbit on his first space mission. He participated in two spacewalks, totaling just under seven hours.

“While living and working aboard the world’s only orbiting laboratory, Whitson and Fischer contributed to hundreds of experiments in biology, biotechnology, physical science and Earth science, welcomed several cargo spacecraft delivering tons of supplies and research experiments, and conducted a combined six spacewalks to perform maintenance and upgrades to the station,” wrote NASA.

The astronaut duo discussed the highlights and challenges of their trip, as well as adjusting to life back on Earth during a news conference on Monday.

Whitson noted during the press conference that one of the most stimulating experiments she worked on during this trip was an investigation into a new antibody drug that targets cancerous cells. The work was conducted in a unique microgravity environment, and the goal of the research is to analyze the effectiveness of the antibody to kill cancer cells while reducing the toxic side effects commonly associated with traditional chemotherapy treatments.

Whitson explained that the microgravity environment allows researchers to observe results of experiments in new ways that wouldn’t be possible on the ground, and provides a “different twist” on basic scientific principles.

Whitson also emphasized the evolution of the ISS in general, and how overall efficiency has increased.

She said that both the quantity and complexity of scientific research conducted on the ISS has greatly improved since her first expedition, and the research could lead to “really exciting results.”

Fischer estimated that between himself and Whitson, they dedicated about 60 hours per week to scientific research.

In addition to the antibody studies, the pair also participated in research dedicated to getting a better understanding of the vision changes that occur in astronauts’ eyes during and after long-duration spaceflight.

According to NASA, more than half of American astronauts experience vision changes and anatomical alterations to parts of their eyes as a result of long-term space flight.

Interestingly, Whitson commented that since her return to Earth, her vision seems to have improved compared to pre-launch of the mission. But that improvement may wear off as her body continues to acclimate to life back on Earth.

The team also did some initial testing on an exercise machine that is much more compact than current equipment onboard the ISS, which may prove useful for deep-space flights in the future.

Fellow NASA astronauts Mark Vande Hei, and Joe Acaba, along with Alexander Misurkin of Roscosmos will pick up where Whitson and Fischer left off. They are scheduled to launch to the ISS on Sept. 12 from Baikonur, Kazakhstan.