Unless there are children in your life of Octonauts-viewing age or you follow popular science news, there’s a good chance you may never have heard of tardigrades. Tardigrades, also known as water bears or moss piglets—because one weird turn deserves another, apparently—are nearly microscopic extremophiles that have been found surviving and thriving in all sorts of inhospitable places on planet Earth, from the Antarctic to underwater thermal vents. Recently they’ve been populating the news cycle, as well, following their confirmed but only semi-intentional arrival on the Moon. Let’s get to know them and their space-faring exploits!
Just what is a tardigrade, anyways?
Discovered in 1773 by a German zoologist, tardigrades are actually a phylum (as in “Kings Play Chess On Fine-Grained Sand”) made up of over 1,100 individual species—all of them tiny, all almost unbelievably hardy. Many have tried to describe their odd appearance, but my favorite approximation comes from Scientific American:
Tardigrades, or water bears, are pudgy, microscopic animals that look like a cross between a caterpillar and a naked mole rat. These aquatic invertebrates are consummate survivors, capable of withstanding a host of extremes, including near total dehydration and the insults of space.
In other words, this:
plus this:
equals this!
Talk about hitting it right on the head!
However, it’s important to note that tardigrades are not in fact microscopic. The babies and smaller species are, but larger species and adults are about a millimeter long and therefore visible—though not in detail—to the naked eye.
Now that we know what they look like, let’s talk a little about where they can live. Extremophiles, as their name suggests, are organisms that can survive in what humans—and indeed the vast majority of life as we have until recently known it—would consider extreme conditions. Here’s a breakdown from Wikipedia:
- Temperature – tardigrades can survive:
- A few minutes at 151 °C (304 °F)[53]
- 30 years at −20 °C (−4 °F)[54]
- A few days at −200 °C (−328 °F; 73 K)[53]
- A few minutes at −272 °C (−458 °F; 1 K)[55]
- Pressure – they can withstand the extremely low pressure of a vacuum and also very high pressures, more than 1,200 times atmospheric pressure. Some species can also withstand pressure of 6,000 atmospheres, which is nearly six times the pressure of water in the deepest ocean trench, the Mariana Trench.[25]
- Dehydration – the longest that living tardigrades have been shown to survive in a dry state is nearly 10 years,[44][45] although there is one report of leg movement, not generally considered "survival",[56] in a 120-year-old specimen from dried moss.[57] When exposed to extremely low temperatures, their body composition goes from 85% water to only 3%. As water expands upon freezing, dehydration ensures the tardigrades’ tissues are not ruptured by the expansion of freezing ice.[58]
- Radiation – tardigrades can withstand 1,000 times more radiation than other animals,[59] median lethal doses of 5,000 Gy (of gamma rays) and 6,200 Gy (of heavy ions) in hydrated animals (5 to 10 Gy could be fatal to a human).[60] The only explanation found in earlier experiments for this ability was that their lowered water state provides fewer reactants for ionizing radiation.[60] However, subsequent research found that tardigrades, when hydrated, still remain highly resistant to shortwave UV radiation in comparison to other animals, and that one factor for this is their ability to efficiently repair damage to their DNA resulting from that exposure.[61]
Irradiation of tardigrade eggs collected directly from a natural substrate (moss) showed a clear dose-related response, with a steep decline in hatchability at doses up to 4 kGy, above which no eggs hatched.[62] The eggs were more tolerant to radiation late in development. No eggs irradiated at the early developmental stage hatched, and only one egg at middle stage hatched, while eggs irradiated in the late stage hatched at a rate indistinguishable from controls.[62]
- Environmental toxins – tardigrades are reported to undergo chemobiosis, a cryptobiotic response to high levels of environmental toxins. However, as of 2001, these laboratory results have yet to be verified.[56][57]
Now, the Moon has extreme temperatures, very low humidity, and elevated radiation levels. Challenging for astronauts, but perhaps no so much so far tardigrades, then. So on that note . . .
Let’s get to the news
As mentioned earlier, there has been a flurry of journalistic activity related to tardigrades lately, starting at the beginning of the month.
On August 5th, Wired published “A CRASHED ISRAELI LUNAR LANDER SPILLED TARDIGRADES ON THE MOON”:
IT WAS JUST before midnight on April 11 and everyone at the Israel Aerospace Industries mission control center in Yehud, Israel, had their eyes fixed on two large projector screens. On the left screen was a stream of data being sent back to Earth by Beresheet, its lunar lander, which was about to become the first private spacecraft to land on the moon. The right screen featured a crude animation of Beresheet firing its engines as it prepared for a soft landing in the Sea of Serenity. But only seconds before the scheduled landing, the numbers on the left screen stopped. Mission control had lost contact with the spacecraft, and it crashed into the moon shortly thereafter.
Half a world away, Nova Spivack watched a livestream of Beresheet’s mission control from a conference room in Los Angeles. As the founder of the Arch Mission Foundation, a nonprofit whose goal is to create “a backup of planet Earth,” Spivack had a lot at stake in the Beresheet mission. The spacecraft was carrying the foundation’s first lunar library, a DVD-sized archive containing 30 million pages of information, human DNA samples, and thousands of tardigrades, those microscopic “water bears” that can survive pretty much any environment—including space.
But when the Israelis confirmed Beresheet had been destroyed, Spivack was faced with a distressing question: Did he just smear the toughest animal in the known universe across the surface of the moon?
The next day, The Guardian reported that “Tardigrades may have survived spacecraft crashing on moon”:
Now, the organisation behind the tardigrades’ trip, the US-based Arch Mission Foundation – whose goal is to find a backup for Earth – has said the organisms may well have shrugged off the collision. “Our payload may be the only surviving thing from that mission,” Nova Spivack, the organisation’s founder, told Wired magazine.
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The tardigrade’s secret is the ability to shrivel into a seed-like pod, expelling nearly all of its water and slashing its metabolism. In this “tun” state, the animals can hunker down and survive conditions that would normally be swiftly fatal. In 2007, scientists discovered that inactive tardigrades are so tough they can survive the harsh radiation and frigid vacuum of space travel.
And so it came to be that there is life on the moon, probably. Lukasz Kaczmarek, a tardigrade expert and astrobiologist at the Adam Mickiewicz University in Poznań, said the animals may well have survived the crash landing. “Tardigrades can survive pressures that are comparable to those created when asteroids strike Earth, so a small crash like this is nothing to them,” he said. The animals could potentially survive on the moon for years, he added.
Dehydrated tardigrades have been revived after years in an inactive state by plunging them into water. Once rehydrated, the animals become active again and feed and reproduce as normal. There is little chance of that happening to those that are lost in space, however. “They cannot colonise the moon because there is no atmosphere and no liquid water,” Kaczmarek said. “But it could be possible to bring them back to Earth and then add the water. They should resurrect.”
Having those creatures unmonitored on the Moon's surface, even in suspended animation, has some scientists concerned.
NASA's Office of Planetary Protection (OPP) has established guidelines for how sterile planetary missions need to be. "Uncontrolled biological contamination of the Moon's surface is not scientifically ideal," said OPP director Dr. Lisa Pratt in a statement after the crash.
We know that nature has been busy cross-contaminating worlds for the past 4 billion years. And hardy little critters like tardigrades have likely already been deposited far beyond the Earth.
The mechanism involves asteroid impacts and so-called impact ejecta. A large literature exists on both theoretical and experimental work tracking the possibilities. The bottom line is that largish asteroid impacts (i.e. roughly 1-kilometer diameter objects and up) tend to spall (shedding of surface material) stuff from a planet and eject some of it with escape velocity or higher. Furthermore, it appears that microbial life and tough organisms like tardigrades have a decent chance of withstanding the pressure and temperature extremes during these shockingly violent launches.
Big impacts can send billions of cm-scale chunks from the surface of the Earth out across the solar system. Some of those pieces may take thousands of years to drop onto other planetary bodies, wending their way through an unseen web of orbital pathways, but they will get there. Indeed, computer modeling of impact ejecta suggest that even far flung places like Titan around Saturn should – albeit rarely – be recipients of pieces of Earth over time. Places like Mars, or the Moon, get far more detritus.
From the point of view of seeking clues to the deep history of life on Earth, this kind of lithopanspermia is fascinating. It may well be that scattered across the surface of the Moon are fossil-like samples taken sporadically throughout life’s terrestrial history. It is also possible that there are samples, even if millions of years old, that contain naturally dehydrated animals like the tardigrade. It is also, of course, possible (albeit with an unknown probability) that there is a happy ecosystem on Mars populated by descendants of terrestrial life.
…
[I]t is conceivable that any life in our solar system has spent the past few billion years in a merry game of natural cross-contamination; mixing it up on a regular basis.
So bio-contamination is probably not actually much of a concern in this case. Great!
There is another area that may still cause some more urgent hand-wringing, though: terrestrial regulations governing space. Or, more specifically, insufficient regulations governing space.
There does exist, since 1967, the
Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, more commonly and efficiently known as the Outer Space Treaty. But it was purposefully designed with a limited scope, as The Verge’s article, “How an international treaty signed 50 years ago became the backbone for space law”, explains:
The hallmark of the Outer Space Treaty is that it isn’t too detailed. “It doesn’t solve every problem,” Henry Hertzfeld, a research professor of space policy and international affairs at George Washington University, tells The Verge. The document is just 17 short articles in length; as a comparison, the Law of the Sea Treaty — a set of rules governing the use of the world’s oceans — spans hundreds of articles in length.
The Outer Space Treaty was never intended to be comprehensive, though. Created when space travel was in its infancy, the agreement was meant to address issues that could arise as space technology advanced. So it is somewhat flexible in its interpretation, as well as limited.
And it turns out that the current tardigrade situation, as well as many other plausible hypothetical situations, are simply not covered by the Outer Space Treaty, or any other laws or regulations at all. Here’s an August 16th article—“
Why Stowaway Creatures On The Moon Confound International Space Law”, also from The Verge—with more:
Technically, international guidelines on interplanetary contamination don’t prohibit sending biological matter and organisms to the lunar surface, since most living creatures can’t survive there. But no governing body had a say in the tardigrade matter at all. The tardigrades were added to the lander by a US nonprofit called the Arch Mission Foundation, whose goal is to create a digital and biological “backup of planet Earth” out in space. The team had approval to add a digital library on the lander, but they didn’t inform Israel or the United States about the added water bears.
“We didn’t tell them we were putting life in this thing,” Nova Spivack, co-founder of the Arch Mission Foundation, tells Mashable. “Space agencies don’t like last-minute changes. So we just decided to take the risk.” Spivack did not want to give further comment to The Verge.
...
While the Arch Mission Foundation didn’t violate any official international regulations for space contamination, the nonprofit may have put Israel and the US in a vulnerable position by not explicitly asking for permission first. And the tardigrades are part of a growing trend of companies that are sending things into space that don’t have any scientific value without prior approval. All of this reopens a long-debated question: who ultimately should have a say in what we send to space?
The Outer Space Treaty did try to answer that question, setting out that national governments are ultimately responsible for any actions impacting space taken by their countries—including any public *or private* entity therein. Unfortunately, as the case of Arch Mission Foundation’s smuggled tardigrades and other examples detailed in the above (uniquely and welcomely wonky) article demonstrate, “private entities have figured out how to shirk the system and international law. And experts worry that other companies may follow suit.”
In a Twitter thread, Monica Vidaurri, a science consultant for NASA’s Goddard Space Flight Center, argued that the accidental spillage of tardigrades on the moon — and the largely unconcerned public response — was a consequence of the absence of much-needed space regulation.
“It is the result of a major gap in accountability for planetary protection and ethics between public and private science, and we have no idea what can happen as a result,” she wrote.
This carelessness, she argues, is the result of a colonial mindset that has led humans to think it’s acceptable to impose ourselves on other environments, both on or off Earth.
“It’s colonialism. It’s imperialism. It’s not for us. And if our science carries on under the same institutions of imperialism, in the name of the same government and not for all of humanity, it is not science,” she tweeted.
There is no easy answer to this challenge, although the United States has begun to reexamine the problem, and hopefully an increasing human-led presence in space will be met with increasingly wise national policies and international frameworks. (Those governing the fictional Federation of Star Trek fame might not be a bad jumping-off point.)
In the meantime, the Earth-creatures-on-the-Moon controversy does give us the opportunity to recall a piece of good news regarding tardigrades. Their superhuman abilities may one day be transferred to us humans! Here’s Scientific American again, in “
Tardigrade Protein Helps Human DNA Withstand Radiation”, to tell you all about it:
A paper published on September 20 [2016] in Nature Communications pinpoints the source of yet another tardigrade superpower: a protective protein that provides resistance to damaging X-rays. And researchers were able to transfer that resistance to human cells.
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“Protection and repair of DNA is a fundamental component of all cells and a central aspect in many human diseases, including cancer and ageing,” says Ingemar Jönsson, an evolutionary ecologist who studies tardigrades at Kristianstad University in Sweden.
This makes the new paper’s findings “highly interesting for medicine”, says Jönsson. It opens up the possibility of improving the stress resistance of human cells, which could one day benefit people undergoing radiation therapies.
Kunieda adds that these findings may one day protect workers from radiation in nuclear facilities or possibly help us to grow crops in extreme environments, such as the ones found on Mars.
Wow, tardigrades are really cool!
First of all: Yes, yes they are.
Secondly: I know, right!
At this point you may be feeling a little bummed that you didn’t know about these cool little critters before. But take heart! Tardigrades are all around us. A handheld microscope or a powerful magnifying glass together with a little persistence should be all you need to find and study these fascinating creatures for yourself. Or, you know, an internet search. And honestly, you could do worse than checking out season 3, episode 2 of the Octonauts. It may be a kids’ show, but it’s always informative and the graphics are pretty cute. And while it’s a good thing that cutting edge knowledge makes its way into children’s media and teaching materials . . . kids shouldn’t get all the fun! Here’s a small clip.