After about three weeks of web spinning, Arabella was shuttled back into her vial, and Anita was released into the box. The results were pretty near the same. Anita’s first efforts were feeble, and after a couple of days and a couple of tries she got the hang of it. She began to spin lovely little webs in space. “It is probably the absence of body weight which disturbed each of the two animals severely during the first days after release from the vial,” Witt and his co-authors write. Then on September 16, Garriott found Anita dead in the box. He collected her body and returned it to the vial. She would return to Earth with the crew for further examination.
The crew splashed down in the Pacific on September 25, and now back on Earth they found Arabella dead too, likely from starvation. It was a long way to go for two spiders. During their flight, Arabella and Anita got a lot of press, their story and pictures in newspapers and on TV. They were famous spiders now, despite the fact that they were dead, and so their curled, dead bodies joined the permanent collection at the Smithsonian. The most interesting finding, write Witt and his co-authors, has little to do with observations about the nervous system but with “the ability of an invertebrate animal with as rigid a behavior pattern as orb-web construction which is relatively independent of experience to find alternate ways to complete a perfect trap for food and thereby increase its chance for survival.”
In 2007 the European Space Agency sent a community of tardigrades, also known as the water bear, into the vacuum of space on the Foton-M3 mission. The water bear is a microscopic invertebrate animal left over from the Cretaceous, and likely even further back, which means it has been around for at least 250 million years. Under a microscope it does look like a little bear, with a barrel-like body, eight little bear legs with claws, and a snout-like mouth used to pierce the cells of the tiny plants, algae, and invertebrates that it eats. On Earth, the water bear is found almost everywhere. It flourishes in mosses and marshes where conditions are generally warm and moist. It has also been found in the most extreme environments: under crushing pressure at ocean depths, at dizzyingly low pressure at mountain heights, in roiling hot springs, and on barren ice shelves. It lives in the wet, warm tropics and in dry, sandy deserts. Nearly unkillable, it is one of the hardiest animals on Earth.
After ten days of exposure to space on the Foton-M3, the water bears returned to Earth alive. A human being exposed to space without protection has about 30 to 90 seconds to live, and up to 180 seconds for Chuck Norris. It’s not just the absence of breathable air that is the problem. It’s also temperature extremes, the absence of atmospheric pressure (vacuum), and radiation. The water bear withstood all of this for ten days. It managed temperature ranges from -272.8 degrees Celsius (three times colder than the coldest temperature ever recorded on Earth) to 151 degrees Celsius (hot enough to bake bread or slow roast a chicken). The vacuum of space had almost no negative effects on the water bear. And it withstood cosmic radiation at a level 1,000 times greater than what we experience here on Earth. The UV radiation from our sun is also over 1,000 times greater in space than here on Earth, and it fries cellular structures and DNA. At this intensity a number of water bears did die, but a number also survived.
How does the water bear do it? The water bear does it by dropping into a dormant state. It reduces the moisture content in its body to as low as 3 percent and hardens the membranes of its cells. In effect, it creates its own protective shell called a tun, a little spacecraft if you will, inside which it waits for conditions to improve. Caspar Henderson writes in his fantastic book The Book of Barely Imagined Beings that on Earth the water bear can remain in this state for 120 years. When conditions improve, the water bear rehydrates itself and goes about its business, a “micro, aqueous Phoenix,” Henderson calls it, rising up from the dead.
There is something even more curious going on here too. In 2015 a team of scientists from the University of North Carolina at Chapel Hill announced that they had successfully sequenced the genome of the water bear. What they discovered is that upward of 17.5 percent of the water bear’s genes are not water bear genes. They come from other species, from bacteria, plants, fungi, and various microbes. Until now, it was thought that such gene borrowing occurred at a much lesser rate among Earth species. The rotifer was the previous champ at 8 to 9 percent, while most animals will carry only about 1 percent foreign DNA. The water bear accomplishes its feat through horizontal gene transfer as opposed to sexual reproduction. As it is coming out of its dormant state and reconstituting its body with water, its cell membranes are porous, even leaky, allowing foreign DNA and other molecules to enter. Some of these foreign bodies may be of no help at all and may even cause death. But some of them work to the water bear’s advantage. Natural selection takes care of the rest, and 250 million years later we have an animal that really is as tough as Superman. It may be that the water bear’s ability to withstand extreme environments is based on the acquisition of these foreign DNA, just as the process of moving into and out of its dormant state to withstand these extreme environments allows the acquisition to occur.
Studying the water bear as it endures the vacuum of space may help answer questions about the origin of life on Earth. Some scientists see evidence for Mars and Earth sharing in the origin of life during the planet-forming age of our solar system, and it may be that life persists on Mars, deep underground—we do not yet know. In 2016 scientists working in Greenland found the oldest fossils yet known—communities of bacteria, known as stromatolites—and they were alive at a time when Earth and Mars were much the same. So if life emerged in the conditions on Earth at that time, it could have emerged on Mars too. Or it’s possible that life began on Mars and then was transferred or migrated to Earth. Species on Earth have always traveled across great distances borne on the wind, flushed down great rivers, riding rafts of flotsam across the seas from continent to continent. So why not through space? Transpermia, as the theory is known, takes into account the possibility that life may travel through space from planet to planet, or even between solar systems. Perhaps life is in the business of traveling about our galaxy, traveling about the cosmos, and seeding suitable planets as it goes. Perhaps the water bear came to Earth from somewhere else. Perhaps it is not to the Earth alone that we belong, but to the great cosmos itself.
In 2011 the California-based Planetary Society, working with scientists in Russia and Germany, set up the Living Interplanetary Flight Experiment to test this theory of transpermia by sending the water bear (along with samples of various bacteria, eukaryotes, and archaea) to Phobos, one of the two moons of Mars. In fact, so likely was it that at least some of the samples would survive deep-space travel and arrive at Phobos alive that the International Committee Against Mars Sample Return positioned itself against the mission. The probability that the samples would contaminate Phobos, and possibly Mars, they said, was too high to risk the science at all. The mission flew anyway, but the spacecraft stalled out in Earth orbit. A programming error on the Russian rocket made it impossible to boost it out of orbit and on to Mars. It eventually burned up on reentry, with fragments crashing into the Pacific Ocean near Chile.