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Why Tardigrades Are So Hard to Kill
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How to Own Land by Standing on It
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The Rule Everyone Invented
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Grab your coffee and let’s dive in.

In April 2019 an Israeli spacecraft called Beresheet crashed into the Moon, and among its cargo were thousands of dried-out animals that, by any normal standard, should not have been worth sending. They were tardigrades, better known by their wonderful nicknames, water bears and moss piglets, and each one looks like a plump eight-legged gummy bear about half a millimeter long. They live almost everywhere on the planet, from Himalayan peaks to deep ocean trenches to the patch of damp moss on your roof. There are likely some within a few feet of you right now. A German pastor named Johann Goeze first described them in 1773 and called them "little water bears" for the lumbering way they amble along on their stubby clawed legs. Up close they have a strange, almost cuddly charm, with a round plodding body and a tube-like mouth built for sucking the juices out of moss and algae. It hardly looks like the toughest animal on Earth.

That reputation rests on a trick called cryptobiosis. When the puddle or the moss around it dries up, a tardigrade lets almost all the water drain from its body, pulls in its legs, and shrivels into a husk called a "tun." Inside it, its metabolism drops to as little as 0.01 percent of normal. In that state it can survive being frozen to nearly absolute zero, heated past the temperature of hot tea, and blasted with about a thousand times the radiation that would kill a person. Japanese scientists revived tardigrades that had spent three decades frozen in a sample of Antarctic moss, and other researchers have squeezed them at pressures far beyond the bottom of the deepest ocean. In 2007 a European satellite exposed a batch to the vacuum and radiation of open space. Many came back to life once they were given a drop of water. Part of the secret is a set of proteins that turn into a kind of glass inside their cells as they dry out, holding everything in place until water returns. Another protein appears to shield their DNA from radiation.

The catch is that all this invincibility applies only when they are dried out and dormant. In their normal plump and active state, going about their business in a film of water, tardigrades are rather fragile and can be eaten or squashed like any other tiny creature. Still, the dormant version may be enough to make them the last animals standing. In 2017 physicists at Oxford and Harvard ran through the worst disasters the universe could throw at Earth, from asteroid strikes to nearby supernovae and gamma-ray bursts. Tardigrades, they concluded, would probably outlast all of them and keep going until the Sun itself dies. Whether the Beresheet passengers survived their own disaster is less certain, since a later study suggested the force of the crash was probably too much even for them. If any did make it, they are scattered across the lunar surface in their tuns, waiting for a drop of water that will never come.

In 1983 a farming family called the Grahams were grazing animals on about 25 hectares of land in Berkshire, England, under an agreement with its owner, the property developer J.A. Pye. When the agreement ran out and Pye refused to renew it, the Grahams did what farmers do and simply kept farming the land. Later offers to pay for it went unanswered. Nobody from Pye came to throw them off, and when the matter finally reached the House of Lords in 2002, the judges ruled that the land now belonged to the Grahams. One of them admitted he reached the decision "with no enthusiasm," which was understandable, since the land was later valued at £21 million. The rule behind it is called adverse possession, alive in nearly every country that inherited the English legal tradition. To most people it sounds like legalized theft. It lets a stranger become the legal owner of your land simply by using it openly for long enough while you fail to notice or object.

The rules are stricter than they sound, because the squatter's use has to be open enough that the owner could have seen it, continuous, exclusive, and without the owner's permission. If someone fences off a corner of your property, mows it, builds on it, and treats it as their own for long enough, they can walk away holding the title. The number of years varies wildly. In California the clock runs for just five years, as long as the squatter has also paid the property taxes, while New York sets it at ten. In England, unregistered land changes hands after twelve years, and for registered land a squatter can apply after ten, at which point the owner is warned and given a chance to object. That warning was added by the Land Registration Act 2002, partly so that inattentive owners would not keep losing land the way Pye had.

The idea behind all this is old and fairly practical. Courts would rather land be used than left idle, and after enough years it is kinder to settle a boundary than to keep reopening it. Pye did not accept that reasoning and took the British government to the European Court of Human Rights, arguing that losing the land without compensation violated its right to property. In 2007 the court's Grand Chamber ruled against the company. There are limits on who can be squatted, though, and you generally cannot claim government-owned land no matter how long you camp on it. Ownership on paper, as property lawyers like to point out, is less permanent than it looks. The Grahams never set out to take anything, and they ended up owning 25 hectares of Berkshire because nobody stopped their animals from grazing.