NASA astronaut Christina Koch once shared her struggles with readjusting to life on Earth after living in space for nearly a year.
Koch broke the record for longest continuous space stay by a woman in 2019-2020, spending 328 days floating on the International Space Station. About three weeks after her Feb. 5, 2020 touchdown, she shared on Twitter: "I may be able to do more pull-ups than before flight, but standing with my eyes closed is still a challenge."
Living sustainably here on Earth presents an ideal way of planning for space, a new study argues. Just ahead of Earth Day, the researchers stress that if we bring the right ingredients of sustainable living to other planets, it's not only good for Earth, but good for people as well.
Related: Earth Day: What is it and why does it matter?
In their March 2023 study, the researchers define a "Pancosmorio theory of human sustainability" in their ingredients for good living. They say that, since human life evolved to deal with conditions here on Earth conditions, an approximation of those conditions (among other factors) is needed to sustain human life in alien locales.
There are three main ingredients, they wrote in the study, which was published in the journal Frontiers in Astronomy and Space Sciences. The first is gravity for good bone health, muscle strength and vision (as microgravity induces eye problems). Next is oxygen, including sustainable backup systems, like using plants. The last is energy, particularly solar energy that can easily be extracted from the moon and other extraterrestrial worlds with a lot of sun exposure.
"For humans to sustain themselves and all of their technology, infrastructure and society in space, they need a self-restoring, Earth-like, natural ecosystem to back them up. Without these kinds of systems, the mission fails," study co-author Morgan Irons said in an April 12 statement from Cornell University, where Irons studies under plant science professor Johannes Lehmann.
In photos: Visions of future space habitats and artificial ecosystems
Creating artificial ecosystems in space is a considerable challenge, as shown by the Biosphere 2 experiments in Arizona in the early 1990s, under management of Space Biospheres Ventures. It was supposed to be a closed-loop system in which simulated astronaut crews would get all the resources they needed on site.
Two crews underwent planned multi-year quarantines in the facility, but things didn't go entirely to plan. The first crew finished its stay but battled issues with carbon dioxide levels and food amounts. The second effort shuttered halfway through in 1994, in part for similar technical reasons, and ownership of the facility was transferred. (The facility is run today by scientists at the University of Arizona, no longer as a habitat but as a laboratory.)
In space, however, partial closed-loop systems on the ISS have met with some success. Examples include a NASA urine-to-water recycling system, and the European Space Agency's (ESA) Advanced Closed Loop System (ACLS) cabinet that recycles carbon dioxide into oxygen. ESA also recently asked the community for their ideas on how to sustainably live off moon resources.
That said, space engineers are also working to overcome numerous environmental issues, such as growing space junk in low Earth orbit and toxic emissions from rocket launches.
Elizabeth Howell is the co-author of "Why Am I Taller?" (ECW Press, 2022; with Canadian astronaut Dave Williams), a book about space medicine. Follow her on Twitter @howellspace. Follow us on Twitter @Spacedotcom or Facebook.