Earth’s first interstellar travelers may be a species that is no stranger to space exploration: the tardigrades. These creatures grow to just 0.5 millimeters in length, but they are some of the toughest animals known to science, surviving even in the vacuum of space.
So far, only five ships have left our solar system and none of them carried biological life. Currently, spacecraft take decades to travel the 18 billion kilometers to interstellar space, but a NASA funded research project is developing solar sail propulsion, powered by Earth-based lasers, which can eliminate the need for conventional rocket thrusters and cover the same distance in just a few days.
Although previous long-distance ships only included messages, like the Discos of Gold of Voyager , making it easier to leave the solar system opens the door to experimenting with living organisms. Stephen Lantin , from the University of Florida, and his colleagues analyzed how much food would be needed to keep various species alive, how much they weigh, and their resilience to the radiation levels and high acceleration that would be encountered on their journeys. Tardigrades emerge as a good choice for low-maintenance pioneer interstellar travelers.
“It would be nice to send humans, but there are some biological restrictions that would make it more favorable to send other organisms, at least on the first few flights,” he says. “It takes a lot of energy to send anything into interstellar space, at least at the speeds we’re proposing, and to do that you need a really small payload.” Unfortunately, such a flight would be a one-way mission, he says.
Tardigrades and the tiny worm Caenorhabditis elegans, another disputed species, have the benefit of being capable of cryptobiosis, a form of extreme hibernation in which animals radically reduce their metabolism under adverse conditions such as desiccation or freezing. Tardigrades are thought to use only 0.01 percent of their normal energy when in cryptobiosis. They have been shown to survive spaceflight and even exposure to the space vacuum in previous missions , and they can have arrived on the moon as part of a failed Israeli mission .
Thomas Boothby , from the University of Wyoming, says that tardigrades have “remarkable” resilience compared to almost all animals, but that interstellar travel is far more extreme than low-Earth orbit.
“I think there would be a lot of things we could learn from tardigrades that would inform how we humans would fare. An important lesson from this type of experiment would likely be to identify tricks that tardigrades use to help them survive and use those tricks to try to develop therapies or countermeasures for humans who face the stress of interstellar travel,” he says.
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Tardigrades May Be Earth’s First Interstellar Travelers