Tardigrades: The last survivors on Earth

July 14, 2017, University of Oxford

The world's most indestructible species, the tardigrade, an eight-legged micro-animal, also known as the water bear, will survive until the Sun dies, according to a new Oxford University collaboration.

The new study published in Scientific Reports, has shown that the tiny creatures, will survive the risk of extinction from all astrophysical catastrophes, and be around for at least 10 billion years - far longer than the human race.

Although much attention has been given to the cataclysmic impact that an astrophysical event would have on human , very little has been published around what it would take to kill the tardigrade, and wipe out life on this planet.

The research implies that life on Earth in general, will extend as long as the Sun keeps shining. It also reveals that once life emerges, it is surprisingly resilient and difficult to destroy, opening the possibility of life on other planets.

Tardigrades are the toughest, most resilient form of life on , able to survive for up to 30 years without food or water, and endure temperature extremes of up to 150 degrees Celsius, the deep sea and even the frozen vacuum of space. The water-dwelling micro animal can live for up to 60 years, and grow to a maximum size of 0.5mm, best seen under a microscope. Researchers from the Universities of Oxford and Harvard, have found that these life forms will likely survive all astrophysical calamities, such as an asteroid, since they will never be strong enough to boil off the world's oceans.

Three potential events were considered as part of their research, including; large asteroid impact, and exploding stars in the form of supernovae or gamma ray bursts.

Asteroids

There are only a dozen known asteroids and dwarf planets with enough mass to boil the oceans (2x1018 kg), these include (Vesta 2x1020 kg) and Pluto (1022 kg), however none of these objects will intersect the Earth's orbit and pose a threat to .

Supernova

In order to boil the oceans an exploding star would need to be 0.14 light-years away. The closest star to the Sun is four light years away and the probability of a massive star exploding close enough to Earth to kill all forms of life on it, within the Sun's lifetime, is negligible.

Gamma-Ray bursts

Gamma-ray bursts are brighter and rarer than supernovae. Much like supernovas, are too far away from earth to be considered a viable threat. To be able to boil the world's oceans the burst would need to be no more than 40 light-years away, and the likelihood of a burst occurring so close is again, minor.

Dr Rafael Alves Batista, Co-author and Post-Doctoral Research Associate in the Department of Physics at Oxford University, said: "Without our technology protecting us, humans are a very sensitive species. Subtle changes in our environment impact us dramatically. There are many more resilient species' on earth. Life on this planet can continue long after humans are gone.

"Tardigrades are as close to indestructible as it gets on Earth, but it is possible that there are other resilient species examples elsewhere in the universe. In this context there is a real case for looking for life on Mars and in other areas of the solar system in general. If Tardigrades are earth's most resilient species, who knows what else is out there."

Dr David Sloan, Co-author and Post-Doctoral Research Associate in the Department of Physics at Oxford University, said: "A lot of previous work has focused on 'doomsday' scenarios on Earth - astrophysical events like supernovae that could wipe out the human race. Our study instead considered the hardiest species - the tardigrade. As we are now entering a stage of astronomy where we have seen exoplanets and are hoping to soon perform spectroscopy, looking for signatures of life, we should try to see just how fragile this hardiest life is. To our surprise we found that although nearby supernovae or large asteroid impacts would be catastrophic for people, tardigrades could be unaffected. Therefore it seems that life, once it gets going, is hard to wipe out entirely. Huge numbers of species, or even entire genera may become extinct, but life as a whole will go on."

In highlighting the resilience of life in general, the research broadens the scope of life beyond Earth, within and outside of this solar system. Professor Abraham Loeb, co-author and chair of the Astronomy department at Harvard University, said: "It is difficult to eliminate all forms of life from a habitable planet. The history of Mars indicates that it once had an atmosphere that could have supported life, albeit under extreme conditions. Organisms with similar tolerances to radiation and temperature as tardigrades could survive long-term below the surface in these conditions. The subsurface oceans that are believed to exist on Europa and Enceladus, would have conditions similar to the deep oceans of Earth where tardigrades are found, volcanic vents providing heat in an environment devoid of light. The discovery of extremophiles in such locations would be a significant step forward in bracketing the range of conditions for life to exist on planets around other stars."

Explore further: More to life than the habitable zone

More information: 'The Resilience of Life to Astrophysical Events' David Sloan, Rafael Alves Batista, and Abraham Loeb, Scientific Reports (2017). DOI: 10.1038/s41598-017-05796-x , www.nature.com/articles/s41598-017-05796-x

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Mark Thomas
5 / 5 (3) Jul 14, 2017
I have watched for decades while science slowly converged on the idea that there is a decent chance for extant subsurface life on Mars. I infer NASA recently selected a young astronaut pursuing her Ph.D in this field because they think this is worth pursuing too. I believe they are correct, but frankly, it doesn't matter. If we discover habitable environments with no life on Mars, that strongly suggests the galaxy may be a lot more open than we realized. There could be billions of lifeless, but otherwise habitable, worlds just waiting for us to arrive and make ourselves at home. Alternatively, if we do find life on Mars, how that life is related to life on Earth, if at all, will also speak volumes about what the rest of the galaxy might be like.

We can see more than enough of the big picture now and the stakes for humanity could not be much higher. We need to get serious about sending people to Mars to get some answers.
geraldbrennan
1 / 5 (5) Jul 14, 2017
"the tiny creatures, will survive the risk of extinction from all astrophysical catastrophes, and be around for at least 10 billion years - far longer than the human race."

You have no idea how long the human race shall survive. That is stupid hubris to presume.
HocusLocus
not rated yet Jul 14, 2017
A whole lot of navel gazing going on in science issues related --- even tangentially -- to asteroid impact. Actually surviving it, even thinking about such survival seems to be the ultimate "someone else's job". Ironically if the asteroid threat was somehow directly accountable to mankind, there would be heightened hysteria and calls for action. Yet... even though anything climate/CO2 related commonly warrants a declarative virtue-signal, typically delivered as a generic phrase of warning (none exists in the article, this IS an off-topic comment)... no one feels compelled to pause from their research long enough to say, "and we really must DO something about the threat of asteroid impact..." It's almost creepy, as if in the midst of science there is this sentiment of, It's God's will...
Da Schneib
5 / 5 (3) Jul 14, 2017
You have no idea how long the human race shall survive. That is stupid hubris to presume.
Considering that semi-modern humans have only been around for a hundred thousand years or so, I'd say it's hubris to suggest we'll be around for a billion. There is no known species that has been around for a billion years; the closest thing to it is the horseshoe crab which is actually a family, not a species. They've been around since the Ordovician which was less than half a billion years ago. Longer lived microbial "species" actually upon investigation turn out to be phyla like the cyanobacteria. If descendants of humans turn out to still be around in a billion years it's a pretty good guess they won't be our conspecifics. At best they're likely to be members of the same class as we are: Mammalia. And it's not necessarily a good guess.
TheGhostofOtto1923
5 / 5 (2) Jul 14, 2017
You have no idea how long the human race shall survive. That is stupid hubris to presume
Sure we do. Humans are a transition species, intent upon replacing themselves with something more suitable. We have externalized evolution. We are both creating more suitable machine versions of ourselves while at the same time replacing bits and pieces of ourselves with more functional alternatives.

In a few thousand years (or less) there will be nothing left that can be called human.

There is nothing that we are made of that can't be replaced with something artificial that will work far better. And that includes that little ball of goo sitting between our ears.

We are obsoleting ourselves.
rrwillsj
3.7 / 5 (3) Jul 14, 2017
HL. in my opinion, scientists/engineers/technicians, as a fuzzy demographic. Are born, raised and educated in the same socially enforced indoctrination as the rest of us.

The troubling viewpoint is that scientists as a caste are pretty much as powerless as the rest of us. Patriotism as enforced obedience to the dictates of the ruling castes of attorneys and capitalists, results in no one with the power to make the difficult decisions. As the plutocracy is simply too incompetent to understand the necessity.

They lack the intellectual vision to direct resources towards the long-term survival of the Human Race.
Shootist
1 / 5 (3) Jul 15, 2017
HL. in my opinion, scientists/engineers/technicians, as a fuzzy demographic. Are born, raised and educated in the same socially enforced indoctrination as the rest of us.

The troubling viewpoint is that scientists as a caste are pretty much as powerless as the rest of us. Patriotism as enforced obedience to the dictates of the ruling castes of attorneys and capitalists, results in no one with the power to make the difficult decisions. As the plutocracy is simply too incompetent to understand the necessity.

They lack the intellectual vision to direct resources towards the long-term survival of the Human Race.


Mumbles? Is that you?
HocusLocus
1 / 5 (2) Jul 15, 2017
HL. in my opinion, scientists/engineers/technicians [...] educated in the same socially enforced indoctrination as the rest of us.


No prominent Neil DeGrasse Tysons in my era returning to the subject often while I was growing up, though Carl Sagan did touch on the subject from time to time as a science imperative. But Sagan was so distracted by the Cold War he jumped on the bandwagon of nuclear disarmament that includes dismantling of such weapons... this sentiment survives to this day... to become a simple and short-sighted, "...put that away son, you won't be needing it..."

Meanwhile evidence mounts (in the 70s) that Chicxulub impact was globally devastating beyond our own survival, despite intelligence. While the US/USSR nuked each other in their minds a grand moral imperative has always existed to weaponize space in defense of the Earth. It has not happened. We have all the time in the world. Once it is sighted THEN time will be short.
HocusLocus
1 / 5 (1) Jul 15, 2017
You have no idea how long the human race shall survive. That is stupid hubris to presume.


It gets worse than hubris. I had never encountered a science article *unfit for children* until I saw this one,
https://medium.co...dec7cb0b
...in which Ethan Siegel tries to convince us that asteroids are 'not dangerous' because the statistical likelihood of dying from one (including the one that kills us all) is small from moment to moment. If he had stopped there it would be of interest only to insurance companies.

But then he goes on, "Hey kids! --- It's nature's way. Go gently into the Good Night when your time is come, as a species." .... "That no life lives for ever; That dead men rise up never; That even the weariest river Winds somewhere safe to sea." If this is some sort of foundation argument, then what is being built?

Failure to consider existential threats as a special case is a mental disorder.
EmceeSquared
5 / 5 (4) Jul 16, 2017
HocusLocus:
Sagan was so distracted by the Cold War he jumped on the bandwagon of nuclear disarmament that includes dismantling of such weapons.


Oh, that annoying little Cold War, just a distraction. Why should the great minds have worked on averting nuclear war instead of working on bringing it closer? Sure, the Soviets ordered nuke launches at least twice, and who knows how many more, and how many US launches were begun - especially by a deranged and drunk Nixon ordering strikes on Vietnam. Nukes are 'not dangerous', right? "Hey kids! --- It's humans' way. Go violently into the Good Night when your time is come, as a species".

Now with plenty of nuke armed barely operational countries facing certain catastrophes as their climates continue to change beyond their governments' capacity to manage, it'll all just blow over. If only 1970s scientists had made even more nukes, we'd all be safe. All it takes is a good guy with a nuke to stop a bad guy with a nuke, amirite?
EmceeSquared
not rated yet Jul 16, 2017
https://en.wikipe..._history
"Most tardigrades are phytophagous (plant eaters) or bacteriophagous (bacteria eaters), but some are carnivorous to the extent of eating other smaller species of tardigrades (e.g., Milnesium tardigradum).[35][36] Others are cannibalistic to their own species."

None are photosynthetic. So when the last of the other plant or animal species tardigrades eat is gone, even the cannibalistic tardigrades will eventually eat each other until starvation and extinction. Presumably long before the Sun engulfs the Earth.

That basic point about tardigrades somehow escaped the researchers at Oxford?
antialias_physorg
5 / 5 (2) Jul 17, 2017
They lack the intellectual vision to direct resources towards the long-term survival of the Human Race.

They have plenty of intellectual vision (you can find any number of such projects on the internet). They lack the resources. Scientists aren't rich and they are not in command of distributing any kind of resources as they see fit (unfortunately). We tend to pay professional liars (lawyers, politicians, CEOs, ...) well. Professional truth-sayers (scientists)? Not so much.

It's a basic failing in the human psyche: Intelligence is an adaptation for making stuff easy for us (by storing many complex issues as few, easily recollected patterns). Liars feed on this by giving us "easy to swallow" lies (or half-truths) - whereas real facts (that scientists give us) aren't easy.

We, as a species, go for the fast food buffet. No matter whether it will kill us.
antialias_physorg
5 / 5 (2) Jul 17, 2017
Considering that semi-modern humans have only been around for a hundred thousand years or so, I'd say it's hubris to suggest we'll be around for a billion.

We can't really be sure how long we'll be around, but there's an interesting way to get an estimate (by Chebychev inequality calculation). It goes basically like this:
Pick any date (say, today). Posit that this date is in no way special in the history of the human race. Add to this the knowledge of how long the human race has been around.

Now assume that this date is neither in the first 5% of human existence nor the last 5% of human existence (i.e. assume, with 90% probability, that we're somewhere in the middle)

Then you can calculate upper and lower bounds (with 90% confidence) of human existence. IIRC this means the human race will go extinct (again: with 90% confidence) some time between the year 3000 and 3000000 (or thereabouts). So yeah: getting to the billion mark *extremely* is unlikely.
Kweden
not rated yet Jul 18, 2017
Error? What about the granite micro-bacteria, which leaves trails in granite, that used to be construed as an isotope trail? You know, the ones that eat granite and have lifespans of at least a billion of years.
They could definitely survive on earth till the end of the sun, and should be able to survive if the earth is ever smashed into separate asteroids.
And they don't need so much water, what happens to tardies when they are dehydrated?

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