Life, in all its unique forms - from the infinitesimally small to the awe-inspiringly
large - can be found, so far, in one place, and one place only: Earth. But while life may seem
to be unique to Earth, what if it wasn’t? What if the flora and fauna and we ourselves originated
from another part of the galaxy altogether? This is Unveiled, and today we’re answering
the extraordinary question: What if life came from another star system?
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Humans have long debated the origin of life on Earth. We know that all the building blocks for
it can be found on our planet, but where did they come from? When Earth was in its infancy,
organic molecules didn’t exist. All the necessary compounds for life were instead
locked up in rocks, the ocean, and the atmosphere. How, then, did life arise from this lifeless
material? It’s a question that has both intrigued and frustrated scientists for generations.
What we do know is that the earliest examples of life date from around three-and-a-half billion
years ago. These are fossilized remnants of something called cyanobacteria or
blue-green algae. But despite the name, blue-green algae isn’t actually
algae. It’s what’s known as a prokaryotic lifeform, a very simple form of bacteria.
It’s thought that these then evolved into more complex lifeforms that utilized photosynthesis.
This, in turn, led to the development of an atmosphere and an explosion of life on Earth. But,
still, how did that first bacteria form? Many theories have been floated over the years.
Generally speaking, for life to exist it needs RNA, DNA, and other proteins. RNA acts like a
messenger, transmitting the information stored in DNA into cells. While both work in tandem,
it’s thought highly unlikely that they appeared at the same time… with it generally believed
that RNA will have developed first of all. How RNA came to be, however, is hotly debated...
with some theories suggesting that it developed deep beneath the ancient sea
via scorching hot hydrothermal vents, while others suggest that a massive nuclear geyser on Earth was
what set everything into motion. Either way, a seriously powerful force would have been needed
to jump-start life on this planet. Science is generally happy with our
origin of life story to a point, but we’re still not quite starting at chapter one.
There are still some early pages to this book that we’ve yet to read or decipher. Which is why some
ponder; have we been looking in the wrong place? Because, what if life didn’t begin deep under the
oceans of Earth, or out of a nuclear fountain, but instead in the furthest reaches of space,
or on another planet altogether? We can trace RNA and DNA back so far, but what about before then?
Panspermia, the theory that microscopic life hitched a ride through space and
ended up on Earth, has been steadily gaining popularity in recent decades.
There have now been various discoveries of meteorites, all over the world map, containing
organic molecules - the suggestion then being that the most simple life might either have started
on other places as well as on Earth, or it didn’t start on Earth at all (and just migrated here).
As for how the meteorite molecules formed, one computer model - created by astrophysicists Fred
Ciesla and Scott Sanford, in 2013 - focussed just on our solar system, but showed how it may have
transformed from initial nebula, some 4.6 billion years ago… to the structured star system of today.
A violent and chaotic process, bathed in intense UV radiation, the model showed how early ice may
have been broken and reconfigured into atoms, and then molecules, before those molecules attached
to meteorites, and eventually (potentially) crashed into Earth. The next question, then;
how could any molecules have survived such a trip through the harsh, cold climate of space?
Again, science has an answer, as this is what researchers from Tokyo University and the Japan
Aerospace Exploration Agency sought to find out with the Tanpopo Mission (or dandelion mission),
held between 2015 and 2018. The experiment involved planting a radiation-resistant bacteria
onto exterior panels on the International Space Station, for up to three years.
Somewhat surprisingly, much of it survived for the full time period… largely because
a thin layer of dead bacteria formed, which protected the rest of the bacteria beneath.
The results led researchers to theorize that some bacteria could potentially survive for up to eight
years in space. While that’s not nearly long enough for interstellar travel, it’s certainly
long enough for a trip from a nearby planet. The Tanpopo Mission makes a strong case, then,
for the possibility of interplanetary panspermia, but what about interstellar panspermia,
too? Could life really survive the long trip from another star system?
Crucially, interstellar panspermia first posits that life does exist throughout the galaxy. But,
still, it’s hundreds, if not thousands or even millions, of years’ worth to travel through space.
All the while being blasted by cosmic radiation. According to some theories, though, life could
survive such a journey, if it became bedded in just the right way under the surface of asteroids.
An asteroid’s rocky outer layers may act as a shield for the molecules of life
to hide behind. But this has always been just a theory. That is, until the arrival of ‘Oumuamua.
In 2017, astronomers discovered the first known interstellar object passing through our solar
system: ‘Oumuamua. With a Hawaiian name meaning “scout”, this celestial object has really got
the scientific community talking. Not only because it’s the first interstellar object
we’ve observed at close quarters, but also because it has some very unusual properties.
So much so, there is still some debate about what it actually is. Is it a comet, an asteroid,
or some kind of alien technology? It’s certainly unusually long, but perhaps the most interesting
thing about ‘Oumuamua is that it’s icy. The fact that the ice hasn’t been blasted off its surface
during its long space journey of at least several hundred thousand years gives us hope that life
could also survive such a perilous trip. You might imagine that ‘Oumuamua is an extremely
rare find for astronomers, and to some extent it was. But then, just two years after its discovery,
another interstellar object was found in our solar system: Borisov. This was especially exciting
because a new interstellar object being found so quickly has encouraged astronomers to re-evaluate
theories on the frequency of interstellar objects passing through our particular part
of the universe. And even on the frequency of them colliding with Earth. A longstanding
theory in palaeontology says that asteroids hit Earth roughly every 26 to 30 million years…
and now, the general predictions in astronomy are beginning to line up with those numbers.
Which means that interstellar panspermia may have had many more opportunities to spread
to Earth than we’d previously considered. But finally, we know how life probably formed
on Earth, how it may form elsewhere, and how it may have travelled here through the cosmos via a
comet or asteroid… but how might it have found its way onto a comet or asteroid, to begin with? Well,
one 2020 study in the International Journal of Astrobiology, by Amir Siraj and Abraham Loeb,
found that interstellar objects could feasibly collect organic molecules just while passing
through a planet’s atmosphere. From there, the study suggests a chunk of space rock or ice might
use the nearby gravitational force to slingshot out of one star system and towards another.
One implication of this is that collisions between worlds and asteroids may not even be
necessary to transfer life, as most other theories suggest. Instead, just a brief interaction high in
a planet’s atmosphere might be enough. And it’s estimated that such an interaction has
happened in our own atmosphere thousands, if not tens of thousands of times already.
But before you go about introducing yourself as an alien lifeform, it should be noted that panspermia
is still a long way off from being accepted scientific fact. The only way to prove that
organic material could survive interstellar travel would be by strapping it to a probe. But that’s a
little tricky, for a couple of reasons. There are space contamination laws to contend with,
and immense, staggering distances at play. But that isn’t to say it won’t be possible
in the future. Exciting developments are being made every day in the world of space travel.
But those are for another video. And that’s how life could have come from another star system.
What do you think? Is there anything we missed? Let us know in the comments, check out these other
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