On this channel I often talk about the possibility of alien life.
But I don’t really draw much of a distinction between levels of life as far as discovering
it goes, I’d be just as happy to detect alien microbial life as I would be in discovering
a full-fledged civilization.
In, other words, I’ll take anything I can get that confirms life in the universe independent
of our planet.
And, while I think intelligent life and civilizations are probably rare, one aspect of life on earth
gives me confidence that we are probably going to find no shortage of simple, or even moderately
complex life in the universe.
It’s the sheer resilience of some species of earth life, so much so that a handful of
species can withstand the rigors of space.
Other than the obvious lack of atmosphere, one major threat to life that space poses
is ionizing radiation.
Exposure to this radiation is measured in units called grays, and a mere 5 grays is
enough to kill a human being, and anything above 8 is certain death for most life on
earth.
There are only a few species of animal that can stand a bit more, such as the German cockroach,
which I suppose unsurprisingly can handle up to 64 grays and also the resilient fruit
fly which can take ten times that.
Most of the microbes also have problems with radiation, e. coli can only handle about 60
grays before it starts dying.
But there are a few organisms on earth that not only can withstand radiation to truly
amazing levels, but can withstand the vacuum of space so much so that we may some day find
them living on some of the other bodies in the solar system, and they also may be among
the last living organisms on this planet when the sun finally destroys it.
The first of these is actually a family of animals rather than a microbe, albeit a very
tiny animal.
It’s the famous tardigrade, a truly amazing group of species that can go 30 years without
eating, live for over 60 and survive a whopping 5,000 grays of radiation.
They can withstand temperatures near absolute zero to above the boiling point of water.
And they are found in all environments on planet earth and can even survive the dryness
of space for a decade in a sort of dried up suspended animation that ends once they are
returned to water.
In one case, a tardigrade that had been bone dry for over 100 years was reanimated, sort
of.
It moved a leg, though no one is really sure if that qualifies as being brought back to
life.
Regardless, that particular tardigrade might not make the best material for a Frankensteinesque
reanimation story.
Tardigrades can even survive astrophysical phenomena, and in fact have survived all of
Earth’s mass extinctions that have occurred since they first evolved.
In a study done by David Sloan and Raphael Batista, link in the description below, they
took a look at the threats that face earth that can cause mass extinctions of most life
on earth and found that gamma ray bursts, nearby supernovas and even asteroids, all
fall short in their ability to cause the extinction of the tardigrade.
Only the events surrounding the evolution of the sun will do it, though even then if
they’ve colonized other places in the solar system, they may continue to persist there.
But even the tardigrade has its limits.
It can’t really be classed as an extremophile like some of the microbes because while it
is incredibly resilient, it’s not really designed for the harsh conditions that it
can withstand.
When dried up or frozen, they can’t reproduce or do what tardigrades in normal environments
do.
And that brings us to something else entirely.
That’s the lichens, some of which seem to be radioresistant.
Jean-Pierre de Vera and colleagues showed that certain types of lichens, protected by
niche environments could survive, photosynthesize and grow on Mars.
Add that with research done on the international space station where certain species of lichens
survived up to 18 months in the naked conditions of space, and you have a possible scenario
of earth lichens colonizing Mars through panspermia.
But now we get to some organisms where radioresistance reaches ridiculous heights.
The first is called Deinococcus Radiodurans, and like the tardigrade can survive multiple
different types of adverse conditions, including very high ionizing radiation three times that
of the tardigrade at 15,000 grays.
Remember, 5 grays kills a human, and 60 kills e. coli.
D. Radiodurans was actually discovered because of its radioresistence.
In 1956, Arthur Anderson was experimenting with sterilizing canned food and while expecting
to completely sterilize a sample with very high radiation, he found that he did not due
to this bacterium and his sample spoiled.
The reason for this bacterium’s resistance is that it can rapidly repair its own DNA
on an order that almost every other organism on earth cannot.
This has led some researchers in the past to wonder if this organism is even from earth.
While the ability to dry out or go without food is useful, there’s no really good reason
for an organism to evolve such resistance to radiation in earth’s low radiation environment.
That opened up the notion that it might have evolved on Mars early in life’s history
in the solar system and was transported here via panspermia, or alternatively perhaps it
spent some part of its evolutionary history in space.
This has been largely discounted however because as resilient as D. Radiodurans is, it bears
much genetically in common with the rest of life on earth.
Work done by Valerie Mattimore of Louisiana State Universe showed that the radioresistence
is more likely to be a happy evolutionary accident brought on by evolving an ability
to completely dry out.
The radio resistance was merely a chance side effect of that.
Or maybe not.
The most radiation resistant organism found on earth is a relative newcomer to science,
discovered only in 2003.
Named Thermococcus gammatolerans, this organism is a mystery.
It’s very different from D. Radiodurans in that it belongs to the archea rather than
the bacteria.
And it likes deep ocean hydrothermal vents where things don’t usually dry out.
While it doesn’t seem to be well-suited for the rigors of space, this organism can
handle radiation like nothing else on earth.
It can sustain a mind-boggling 30,000 gray dose of gamma rays and no one knows why.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently wondering if there
are any dormant tardigrades in the room, I’m surrounded!
and be sure to check out my books at your favorite online book retailer and subscribe
to my channel for regular, in-depth explorations into the interesting, weird and unknown aspects
of this amazing universe in which we live.