Learn about the toughest animal on the planet: tardigrades

Eons from now, when some believe few species will still exist, tardigrades, also known as “water bears” will be one of the last standing organisms on Earth. Professor of science at Harvard University, Avi Loeb, joins Hari Sreenivasan via google hangout to discuss one of the toughest animals on the planet.


Eons from now when some believe few species will still exist, tardigrades, also known as water bears, will be one of the last ones standing on the planet.

Professor of science at Harvard University Avi Loeb joins us via Google Hangout to discuss one of the toughest animals on the planet.

Thanks for being with us.

So, give us an example of how tough a tardigrade is.

Well, the tardigrades were taken to space about a decade ago.

Many of them survived, more than half.

And then they were able to reproduce as soon as they were put back to water.

They were able to reproduce, and they had viable embryos as soon as they were put back to water.

Up there in space, they were dehydrated.

They were exposed to ultraviolet radiation.

And they were put in a vacuum.

That leads people to conjecture that it's possible for them, I mean, since they are a very good astronauts -- they have their own suits, they don't need to be put under special conditions -- that if, for example, there is a rock flung out of the Earth as the result of an asteroid impacting the Earth, potentially they could survive the journey and deliver, transfer life from Earth to another planet, for example, Mars.


So how did we discover them?

Well, they exist everywhere on Earth.

Since they are so sturdy, they are able to survive extreme conditions.

We find them in almost every environment including environments that have very high temperatures close to the boiling point of water down to very cold temperatures.

They seem to preserve themselves even if they are dehydrated, without any water for a while.

They also have, their DNA's very special.

It's able to repair itself.

And so studying them could have some useful medical implications.

Perhaps we can learn how to cure diseases or find some other medical benefits from knowing how they do it.

The important thing to realize is that it's very difficult to kill them.

And so what we were out to examine in the work that we did, the research that we did, was whether any astrophysical catastrophe, any explosion or impact from, let's say, an asteroid on Earth, could eliminate all forms of life including tardigrades.

And what did you find?

We found that they would likely survive almost everything except the death of the Sun.

You know, the Sun is roughly at the middle of its life right now.

In about 7 billion years, it will consume all of its nuclear fuel, and so its... Life as we know it will cease to exist on Earth.

But other than this catastrophe, it seems like they are resilient to other things, like for example an exploding star nearby would not really kill them because the chance of the star being close enough is very small.

Also, an impact of an asteroid will not kill them during the next few billion years.

The probability is less than one in a million, we calculated.

And so they're really out there for the long run.

It's possible that they are agents of transferring life between planets.

This is a process called panspermia.

So if life exists on one planet, it may actually move to other planets.

We now know, for example, of a seven-planet system around a star called TRAPPIST-1, which is about several tens of light years away.

And those seven planets are very densely packed.

So three of them are actually in the habitable zone, in the region where liquid water may exist on their surface, and the chemistry of life as we know it might take place there.

First of all, you have three rollings of the dice to get life on one of these planets.


That increases the chances of life, but moreover, once life forms on one of the planets, it can transfer itself to another one by rocks flying between the planets, landing.

We know that rocks from Mars came to Earth.

We find such rocks.

And so not only that these planets, you know, there are more of them that are in the habitable zone, in the solar system, but also they are densely packed, so it's easier to transfer life from one to another.

And if you ask what kind of animal is best suited to be an astronaut, it's those tardigrades.

How long do they live?

Well, it depends on the conditions.

They don't live very long.

They're roughly one millimeter in size or less than a millimeter in size.

And they could live for a while, but that really depends on under which condition you put them.

I mean are we talking years or are we talking weeks?

We're talking years typically.


How long can they go without those things?

So when they went up to space when they didn't have water, when they were in a vacuum, when they were in the colds of space, how long did they survive?

That was roughly 10 days or so, a week that they were able to... once they were brought back to Earth and put in water, they were able to reproduce.


You know, you're describing something close to the fountain of youth meets the Highlander.

Like some sort of unstoppable force that has to be killed only by the evaporation of our Sun and all the oceans' boiling.

But then also there's a certain magic to the regenerative quality of their DNA that could be something that extends our lives or cures our diseases.

Yeah, that's fascinating.

I mean, we are imperfect animals.

We suffer diseases, and we have a finite lifetime.

If you think about it, there's no reason why we can't optimize our bodies to be much, much better and much longer-lived, much more resilient to conditions.

We are extremely sensitive to changing conditions.

So, you know, if, for example, the climate would change on Earth, one possible remedy for that is to make people more resilient.

And be like water bears.

All right.

Avi Loeb, thanks so much for joining us.

Thank you.

My pleasure.