Life in space is partially shielded by artificial gravity.

Astronauts' health may be compromised by the harsh environments they encounter on missions to the Moon, Mars, and beyond. NASA researches the effects of space on "model organisms," or other forms of life that are biologically comparable to humans, to prepare for future long-duration missions. This includes studying the impacts of changes in gravity, radiation, and other factors. Recent research on fruit flies on the ISS indicates that space travel affects the central nervous system but that artificial gravity mitigates some negative effects.

"Microgravity puts the central nervous system at risk, suggesting that countermeasures may be needed for long-duration space travel," said Dr. Janani Iyer, a Universities Space Research Association (USRA) project scientist at NASA's Ames Research Center in California's Silicon Valley and co-author on the paper published today in Cell Reports. To ensure the safety of future explorers as we return to the Moon and Mars, we must find ways to mitigate the negative consequences of microgravity. Studies like this are crucial to understanding how astronauts adjust to life on Earth after spending time in space.

Since fruit flies are so similar to human beings, they make great research subjects. Much of what happens at the molecular and cellular levels in humans also occurs in flies. Since around 75% of human disease-causing genes are also found in fruit flies, studying them can shed light on how the space environment might affect human health. Similarly, a fly only lives for around two months and can breed twice. Scientists can learn more about the flies' biology in a shorter time because the three weeks the flies spend in space is similar to about three decades of a human's existence.

Knowing the Seriousness of the Predicament.

In this experiment, researchers used the Multi-use Variable-gravity Platform (MVP), a new piece of hardware capable of housing flies in varying gravity levels, to send fruit flies on a month-long voyage to the International Space Station. When the flies were living and reproducing in this apparatus, they could feed on fresh food. The MVP's use of individual containers made it possible to keep together generations of fruit flies that had previously been kept apart. One set of fruit flies on the space station experienced microgravity the same way humans do. The centrifuge, an apparatus that spins to simulate gravity, was used to expose another group to artificial gravity on the space station, simulating the force of Earth's gravity. Cameras installed in the station's hardware captured the "flyonauts" antics while in orbit. Some of the flies were frozen at various times and sent back to Earth so that researchers could examine the expression of genes at those times.

To continue their research, scientists at Ames sent the fruit flies back to Earth in a SpaceX Dragon capsule, down in the Pacific Ocean. Scientists at Ames worked nonstop for two days to sort the flies and conduct behavioral and metabolic testing as soon as they arrived. Data from "flyonauts" were compared to that from a group of flies that remained on Earth as a control experiment.

This was the first study to consider space's effects on the neurological system holistically. The researchers studied fly behavior by watching them move around in their natural environment, analyzing cellular changes in the fly brain, determining the effects of gene expression variations on the nervous system, and other methods. A wide variety of changes were detected, some of which could be seen immediately by examining the footage from the cameras installed in the MVP's storage areas. In contrast, others necessitated additional investigation once the craft had returned to Earth. Flying behavior and the ability to rise the following landing were the characteristics examined. After landing, the flies tested their abilities by tapping on the top of their container, eliciting the insect's natural response of climbing higher. Despite being more active in microgravity than in the artificial Earth gravity, flies had trouble with this climbing test after returning to Earth.

Neurological alterations in flies exposed to microgravity were discovered through further study upon their return to Earth. Flies exposed to artificial gravity in space aged differently as they readjusted to life on Earth following their journey. They had difficulties analogous to microgravity-bound flies, albeit on a milder scale.

Creating a Foundation for Future Research.

This study's findings, which demonstrate that spaceflight produces stress in the fly cells, also suggest that this stress has deleterious behavioral and neurological effects and alterations in gene expression in the fly brain. While prolonged exposure to microgravity in space presents serious health risks, artificial gravity can mitigate the effects of this condition on a fruit fly's nervous system in the short term.

These findings cannot be extrapolated to the human experience of long-term space travel due to the significant biological differences between fruit flies and humans (despite some shared genetic material). Still, they pave the way for future research into protecting astronauts from the effects of shifting gravity on their bodies.

Dr. Siddhita Mhatre, a senior scientist at KBR Wyle in Ames and co-author of the paper, said, "With the upcoming long-duration deep space missions, where astronauts will be exposed to varying levels of gravity, it is imperative that we understand the impacts of altered gravity on the neurological function." Possible future mission extensions are possible if artificial gravity can be used to postpone space-related deficits. And flies in space with astronauts will aid in our ongoing efforts to keep astronauts healthy.