What is Astrobiology?
Humans spent thousands of years gazing at the night sky and wondering about
the presence of life elsewhere. Could it be in our solar system?
Could it be on some other blue planet around another star? Nobody ever knew. But such
thoughts have found their expression in fiction, scientific missions and religions worldwide.
Pondering the rise of life on our planet was not only a philosopher's but also
an ordinary people job. Creation myths have been
fundamental to every civilization and culture and reflected the profound
resonance of the question of our origins. What about today? Did we make some steps forward?
Today, astronomers have pushed back our understanding of the origins of
the universe to tiny tiny fractions of microseconds of the big bang.
However, we can't yet give any satisfying definition of life,
nor yet point to the exact time and conditions when the organic matter first went from unanimated
to animated, from nonliving to living. It was about 50 years ago when humanity
began to extend its presence into space, first with robots and then with humans.
As this tentative expansion of our species into other worlds continues, basic questions remain
unanswered about the long-term adaptation of living organisms to other environments.
For example, we often think about Mars as our second possible home,
but we do not know what the effect will be of living for years on Mars
(in fact, the pull of gravity on Mars is about one-third that of Earth).
Astrobiologists try to answer this type of questions.
But what is exactly astrobiology?
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Let's start by simply answering the question: What's astrobiology?
As it's easy to imagine, Astrobiology is the study of life in the universe.
Do you think it is an easy task? Well, I'm sorry to disappoint you,
but life in the universe is actually one of the hardest things we can study.
But let's go back for a moment to when the term Astrobiology was invented.
It was only in the 50s in the 1950s space-age that the term Astrobiology was coined.
It was used to define the study of the biological impact of space missions
and to define the study of the search for extraterrestrial life.
Later, famous scientist Carl Sagan brought Astrobiology to the public
and to the scientific community, and the field began to gain recognition.
So nowadays astrobiology is defined as the science that studies the origin, distribution and
evolution of life in the universe, and it takes several branches of science: biology, geology,
astronomy, physics, chemistry, but also engineering and sociology and together.
Astrobiologists can work alone on particular scientific questions,
but often astrobiologists from different scientific disciplines
work together to examine complex questions that no one field can answer alone.
When we think about life in other words, what we immediately start to imagine is little green men
or maybe tall intelligent species that invade our home earth on their technologic spaceships.
But this is science fiction. Do you want to know what we
really know about life in the universe? Well if we want to speculate about life,
in other words, what it could be? One of the logical starting points
(and maybe the only one!) is to start by looking at our own planet.
In fact, for now, the only known planet-hosting life is Earth!
You'd say this is pretty obvious, right? So what astrobiologist do next?
They use a method called “the great analogy”. In short terms, they use the knowledge that
they have from life on Earth, how it originated and evolved.
Then they try to understand how to extrapolate that knowledge to other environments in the
universe, such as our solar system. That's why the understanding of the
origin of life on Earth is the main key in order to give a push to astrobiology.
The question now is...what do we know about life on Earth?
We know that here on Earth life emerged around 3.8 billion years ago, probably in the deep oceans.
Why? Well, we know that back then the
earth was not the same as today. What do we mean? We mean that if you were here, you could have
not been able to breathe. Because there was no oxygen
at all, and there was no ozone layer! This means that we had a lot of radiation,
and it brings us to the conclusion that the first forms of life would have to be
anaerobic: they would have to avoid radiations and to grow up without oxygen.
That's why we think it originated in deep oceans: there the radiation doesn't hit.
These are our first clues about what it takes for life to emerge:
liquid water and organic molecules. What we think is that the oceans
brought the molecules around and eventually the right molecules
met at the right time, and at the right place. That's how astrobiologists think life emerged.
Also, by looking at the different life forms we study every day,
we realize that biodiversity is amazingly big! Every day we find a new variety of organisms
that live in places that we thought no life could ever exist.
They are called extremophiles. An extremophile (from Latin "extremus"
meaning "extreme" and Greek philiā (φιλία) meaning "love") is an organism with optimal growth in
environmental conditions considered extreme in that it is challenging for a carbon-based life
form, such as all known life on Earth, to survive. These organisms are dominants in the evolutionary
history of the planet. Dating back to more than 40 million years ago, extremophiles have continued to
thrive in the most extreme conditions, making them one of the most abundant lifeforms.
These microorganisms can live at temperatures above 100°C!
Also, they live in acid rivers or very salty lakes, and they help us set the limits of life.
Since one of the most extreme environment is actually space, astrobiologists asked themselves:
can life survive in space? That's why they have done a
lot of experiments in situ: they actually have sent bacteria and other microorganisms to space,
put them on the outside of the International Space Station,
where they are exposed to the real space vacuum and the real space radiation,
so they stood there for months and what they found out is that many of them actually survived.
This is a sort of revolution because it makes us wonder where
else in the universe can life survive!
so the first place we actually look, of course, is our own solar system.
We begin by looking at the moon, we went there. There are not these teams, there is no life there,
but then we focus on other things.
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Europa, Jupiter's moon. Did you know that the
surface of Europa is made of water ice? Many scientists think that beneath the frozen
surface is a layer of liquid water, literally an ocean! which is prevented from freezing by
the heat from flexing. How do we know it?
Evidence for this ocean includes geysers erupting through cracks in the surface ice,
a weak magnetic field and chaotic terrain on the surface, which could have been deformed
by ocean currents swirling beneath. At the bottom of this ocean world, it is
conceivable that we might find hydrothermal vents and ocean floor volcanoes. On Earth, such features
often support very rich and diverse ecosystems. Could therefore Europa host (or have hosted) life?
Titan, Saturn' moon. Titan is the only moon in the
solar system with a substantial atmosphere. The atmosphere consists mostly of nitrogen,
which is an important chemical element used in the construction of proteins
in all known forms of life. Recently, radar observations have detected the
presence of rivers and lakes of liquid methane and ethane and possibly the presence of cryovolcanoes.
Cryovolcanoes are...volcanoes that erupt liquid water rather than lava!
This suggests that Titan, like Europa, has a subsurface reserve of liquid water.
Although its distance from the sun (it's very cold on Titan for liquid water!),
the bountiful chemicals available on Titan have raised speculation that lifeforms – potentially
with fundamentally different chemistry from terrestrial organisms – could exist there.
Mars. Mars is one of the most Earth-like worlds
in the solar system. It has a 24.5-hour day, polar ice caps that expand and contract with the seasons
and a large array of surface features that were sculpted by water during the planet’s history.
Scientists detected the presence of a lake beneath the southern polar ice cap, which makes Mars a
very interesting candidate for life. They also found methane.
This is amazing because it could be produced by biological processes, even though the actual
source for Mars' methane is not yet known. We just have to keep hoping and bringing
information from the Martian soil, maybe with the fantastic help of Perseverance and Ingenuity!
As one can imagine, while astrobiology is a relatively young field,
it has a secure and promising future. Astrobiology research has a significant impact on how agencies
such as NASA and the European Space Agency plan for current and future space missions.
Many recent missions were launched with the aim of exploring worlds in our own solar
system, and find signs of past, present or the precursors of life, including Mars.
One of the most famous missions was the Cassini mission,
which gave us a better understanding of Saturn and its moons (such as Titan).
Today, we are waiting for the launch of the James Webb Space Telescope,
which will allow us to begin searching for habitable planets outside our solar system.
Communicating the discoveries and excitement of astrobiology has been understood
as a fundamental requirement since the early development of the field.
Meeting this objective has taken various forms. One element was a common forum, embodied in the
Astrobiology Science Conference held biennially, that today attracts over 800 scientists from
over 30 fields. With meetings in 2000, 2002, 2004 and 2006 that have continued to grow in
attendance, the conference remains a forum where scientists are encouraged to push the boundaries.
What about the future of astrobiology? On NASA's website we can read:
<<The first decade of astrobiology has laid significant groundwork for the understanding
of the genesis and evolution of life in the universe. Fieldwork has provided fossils,
organisms, and ecosystems that have all led to significant insight into the early Earth,
possible models for origins and a huge expansion of the recognized environmental limits of life.
Laboratory work, coupled with astronomical observation, has added another significant
piece of the puzzle and continues to provide clues and refine models. Missions are just beginning
to take astrobiology to entirely new levels of understanding. Given the timeless fascination with
questions of the origins and prevalence of life, astrobiology will endure long into the future.>>
"This video ends here! Thanks for watching everyone! Is there something more you want
to hear about astrobiology? Let us know in the comments below!
See you next time on the channel!