The last survivors on Earth
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Although
much attention has been given to the cataclysmic impact that an astrophysical
event would have on human life, 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 go on 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.
The
research implies that life on Earth in general, will go on 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.
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.
Tardigrades
are the toughest, most resilient form of life on earth, 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 (2x10^18 kg), these include (Vesta 2x10^20 kg) and Pluto (10^22 kg),
however none of these objects will intersect the Earth’s orbit and pose a
threat to tardigrades.
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, gamma-ray
bursts 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.’
"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.’
"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.’
