Space agencies like NASA and ESA are funding research to see what humans can learn from animals that are able to stop eating and producing waste for several months, writes Le Monde journalist Nathaniel Herzberg.

Hibernation seems tailor-made to help humans explore outer space. Developed by many animal species to cope with the scarcity of resources in winter, it offers potential answers to three of the main challenges of space travel. First, the hope of drastically reducing onboard mass. "This is one of the obsessions of the space agencies," said Alexander Chouker, an intensive care specialist at the University Hospital of Munich and co-leader of the group of 20 experts on hibernation at ESA. "Because it affects the size and power of the spacecraft, but also because each kilo on board costs more than 10,000 euros. Imagine what this means for a crew going to Mars, a two-and-a-half-year mission. But animals that hibernate stop eating and drinking, and no longer produce waste. That's a godsend."
Another constant concern of space agencies is protecting astronauts' muscles and bones. "Gravity alone imposes an action on our muscles," noted Fabrice Bertille, from the Hubert Curien Interdisciplinary Institute in the eastern French city of Strasbourg, whose research on bear hibernation is supported by the ESA. "In the International Space Station, in microgravity, despite continuous exercise, astronauts face serious problems of muscle wasting, and when they come back, they are at risk of bone fragility. In a more constrained environment and over a longer period of time, this can become critical. However, bears do not encounter these difficulties. They lose 15% of their muscle in the first month, then nothing."
Finally, space holds an invisible, but pernicious danger: cosmic rays. On Earth, the magnetic field that surrounds our planet protects us from this radiation emitted by the sun and other stars. However, beyond a distance of 50,000 kilometers from the Earth's surface, we are naked to the protons, ions and X-rays of the solar wind. It is out of the question to surround a vessel with a lead shell, as the weight would prevent it from flying. Other, lighter materials are being tested. But early experiments, conducted for NASA in the 1960s, and especially a more recent study conducted at the Helmholtz Center for Heavy Ion Research in Darmstadt, Germany, for ESA, have established that rats – a non-hibernating species, like us – that were artificially placed in a state of torpor were largely protected from ionizing radiation, a likely effect of reduced cellular metabolism.
Can such "synthetic torpor" be applied to humans? In the United States, Europe and Japan, researchers are working on it. They put forward several arguments. First of all, there have been some examples over the last century of humans miraculously spared from death due to cold exposure by what looks like hibernation. Hominid remains, found in Atapuerca, Spain, dating back 500,000 years, to the middle of the Ice Age, also seem to testify to our ancestors' ability to hibernate. "Hibernators are found in all groups of mammals, even primates," said Alexander Chouker, "and they don't have specific genes. I don't see what would prohibit us from doing so."

Read the full article here: https://www.lemonde.fr/en/science/article/2023/03/13/hibernation-a-closely-studied-option-for-extended-space-travel_6019088_10.html