Astronauts Exhibit Surprising Ability to Gauge Distance in Space

In a study led by York University, researchers have discovered that astronauts possess a surprising ability to orient themselves and estimate the distance they travel in space, even in the absence of gravity.

Predictions. Predicted distributions of the self-motion gains (as a measure of accuracy, see methods for definitions) and the self-motion deviations (as a measure of precision, higher deviations mean lower precision) for the two postures sitting upright (red) and supine (blue). Exposure to microgravity was hypothesized to show the same trends as when supine. Either the gain may become noisier (Hypothesis 1, see panel A) or both noisier and with a higher gain (Hypothesis 2, see panel B). Different panels depict the expected data when Hypotheses 1a and 1b are true (A) or when Hypotheses 2a and 2b are true (B). Credit: npj Microgravity (2024). DOI: 10.1038/s41526-024-00376-6

The study, conducted in collaboration with the Canadian Space Agency and NASA, has significant implications for crew safety in space. It also offers potential insights into how aging affects balance systems on Earth, according to the study's lead, Professor Laurence Harris from the Faculty of Health.

Harris, an expert on vision and the perception of motion, explains that the perception of gravity has been repeatedly shown to influence perceptual skill. "The most profound way of looking at the influence of gravity is to take it away, which is why we took our research into space," says Harris.

Harris and his team, which includes professors Robert Allison and Michael Jenkin from the Lassonde School of Engineering and several postdocs and graduate students, studied a dozen astronauts aboard the International Space Station (ISS). The ISS orbits about 400 kilometers from the Earth's surface, where Earth's gravity is approximately canceled out by the centrifugal force generated by the station's orbit. In this microgravity environment, movement is more akin to flying.

The researchers compared the performance of the astronauts before, during, and after their year-long missions to the ISS. They found that the astronauts' sense of how far they traveled remained largely intact. Harris notes that it's possible their research was unable to capture early adaptation that may have occurred in the first few days, but adds that "it's still a good news message because it says that whatever adaptation happens, happens very quickly."

Space missions are not without risk. The ISS is sometimes hit with small objects that could penetrate the vessel, requiring astronauts to move to safety. "Astronauts need to be able to go to safe places or escape hatches on the ISS quickly and efficiently in an emergency. So, it was very reassuring to find that they were actually able to do this quite precisely," recalls Harris.

The study, recently published in npj Microgravity, is the first of three papers that will emerge from the research investigating the effects of microgravity exposure on different perceptual skills, including the estimation of body tilt, traveled distance, and object size.

Harris says research shows exposure to microgravity mimics the aging process on a largely physiological level. However, this paper finds that self-motion is mainly unaffected, suggesting that the balance issues that frequently come from old age may not be related to the vestibular system. This indicates that the issues involved in falling may not be so much in terms of the perception of how far they've moved, but perhaps more to do with how they're able to convert that into a balance reflex.