[BLANK_AUDIO] We've learned what astrobiology is. It's always very useful in Science, if you Want to get some perspective, to
understand the history. Because the history of a subject can tell
you how you've got to the place you're at At the moment and what it was that led to
the state of knowledge that we have today. So let's look at the history of
Astrobiology and get An overview of some of the early thoughts
in this field. And how it is that we have come to the
state of knowledge that We understand about the possibilities of
life beyond Earth today, and Our understandings of the history and
evolution of life on Earth. You'll often here people say that
astrobiology Is a very new science, an emerging
science. It's certainly true to say that
astrobiology has Developed very rapidly in recent years,
and the experimental Methods that are now being developed, new
missions and New telescopes, are making this a subject
that's advancing At a remarkable rate.
But it's certainly not a new science. People have been contemplating the
possibility Of habitable worlds, for a long time. This is a really rather remarkable Statement by Metrodorus, an ancient Greek
philosopher. Who was actually a student of Democritus, Who first proposed the atomic theory of
matter. And this is in loose translation of what
he said. He said, it would be strange if a single Ear of corn grew in a large plain, Although only one habitable world in the
infinite. Metrodorus was expressing the idea that if
you Go into a field it's very unusual to see One ear of corn growing in the middle of a
field with no other corn around it. Generally if you go into a field and you
see corn you'll see a lot of it. And he wondered if there is life on this
planet, then surely there Must be other worlds with life as well.
Well, the ancient Greeks didn't quite have
the Same perception as the heavens that we do. They don't under, they didn't understand
about planets, and They didn't understand the nature was of
other stars. But nevertheless this was a remarkable
statement for people thinking in early Years astrobiology over 2,000 years ago
about the possibility of inhabited worlds. As we go on through history we find other
speculations that are just as remarkable. In the 16th century during the Renaissance
this was a statement made by Giordano Bruno, who was an astronomer
speculating About the possibility of planets beyond
Earth. And it's worth reading what he said. He said in space there are countless
constellations, suns, and planets, we only See the suns because they give light. The planets remain invisible for they are
small and dark. There are also numberless Earth's circling
around their suns. Now if you think about this statement
today, in an age where we are beginning to Detect Earth-like planets around other
stars, this is A truly remarkable speculation for the
16th century. I'm not a great fan of calling people
fathers or mothers Of particular fields of science, I don't
think It does good things for the human ego. But if you really want a father of Astrobiology, you would probably give it
to Giordano Bruno, person who speculated on the
presence of Other Earths orbiting other stars in the
16th century. Bruno unfortunately was burned at the
stake in 1600, not just for His astrobiological speculations, he did
other things that incurred the wrath of His religious superiors. But he was the first astrobiologist at
least to meet His fate speculating amongst other things
about life beyond Earth. The invention of the telescope allowed us
to Go beyond these speculations, to see
planets around other Stars, and to start to form more empirical Ideas about whether other planetary bodies
could sustain life.
And you might think that Once the telescope had been invented there Would be a lot less speculation, because
now We'd have real data about other planetary
bodies On which we could base ideas and
speculations. But in fact, remarkably, completely the
opposite happens now We have telescopes, we can see other
planetary bodies. But we don't have enough information to
know what their environments are like. So now we've got all these new planets on
which we can speculate about the presence Of other life. And the invention of the telescope of
Galileo, and you Can see here one of the first images that
he Looked at, which was the moons Jupiter,
the four largest Moons of Jupiter, now called the Galilean
moons of Jupiter. This invention of the telescope and its
widespread use led to the discovery of Planets that caused speculation to run
riot during the Enlightenment. This is A speculation by the famous scientist
William Hershel, who wrote, whilst Observing the moon, by reflecting a level
on the subject I'm almost Convinced that those numberless small
Circuses we see on the moon Are the works of the Lunarians and may be
called their Towns. Herschel was observing asteroid craters on
the Moon, craters that seemed almost perfectly
circular. So circular, they couldn't have possibly
have been formed By natural processes. The must be the work of an intelligence,
and he believed that the Moon might be inhabited by Lunarians, who Were constructing these fortifications on
the moon. And even Christian Huygens, famous
astronomer, Observed spots on Venus, Mars, and
Jupiter. Spots that we now know are features of Storms and, and deserts on the surface of
Mars. And he concluded there were clouds and Water and he stated, the taste of music
with the inhabitants of Venus
And Jupiter is at a high level, similar to
that Frenchmen or Italians. Now these observations today seem crazy to
us and they seem crazy particularly Because they came from extremely erudite
scientists That achieved remarkable things in their
field. But it shows how with a very limited set
of Data people began speculating about life
on other planets and I Should say that these speculations are
also a warning from the past. A warning about being too optimistic in Astrobiology and we should be careful
today In learning the lessons from our forebears About over speculation with very little
data. Even in the 20th century, speculation runs
riot. Percival Lowell the Astronomer who
observed lines Across the surface of Mars, an optical
processing Trick of the human brain which he
interpreted To be canals, built by a dessicated dying Civilization on Mars, trying to channel
water from The polar icecaps to the equatorial
regions of Mars. And he observed these canals over and over
again. So convinced was he, he wrote this Every
opposition is added to the assurance that Canals are artificial, both by disclosing
their peculiarities better and better and By removing generic doubts as to the
planet's habitability. The first person to really connect
habitability with Intelligence on a planet in our own solar
system. We now know, of course, there are no
canals on Mars. Percival Lowell was deluded by his
observations. But it shows that even in the 20th century
people thought There might be intelligences on other
planets in our solar system. Aliens still Grip the human imagination. You only have to watch films produced by Hollywood and other production companies
around the world. Aliens are pervasive throughout popular
culture, from Star Wars to The Extraterrestrial, to the War
of the
Worlds, and on and on it goes, a long list
of aliens that we've seen in films. So you can see how, optimism about
astrobiology in Particular intelligent life still grips
the human imagination and We have to be very careful to separate What our imagination wants us to believe
and What the data, what the knowledge that we Have from telescope and missions, is
really telling us. That is a very important lesson in
astrobiology and indeed in any science. In the 1950's and early 1960's, the space
age began to Unfold, and with it, the possibility of
sending spacecraft to other planets. And we started to get views from
spacecraft orbiting Mars and Venus. And these views were rather depressing. On the left hand side there you can see an
image from Mariner 4 from 1965. And Mars looks like A dead desert, there's no obvious canals
there, no intelligent civilizations. And on the right, you can see an image
taken by The Soviet Venera spacecraft, that landed
on the surface of Venus. And again no Venetians playing music like Frenchmen or Italians, just a dead
planetary surface. And these visions of our solar system
really Caused I would say almost a sense of
depression Even among scientists during that period
about The possibility of life throughout our
solar system. No evidence of civilizations, not even any
evidence for Simple life forms, even microbial life on
these planets. And so the early years of the space age,
were a period Where people began to backtrack in their
optimism about life beyond Earth. But ironically, as these spacecraft
improved, and As our cameras improved, we began to see
details. Details that suggested that we might not
be quite as negative, as we Thought we needed to be in the early years
of the space age. People began to see valley networks on the
surface Of mars, outflow channels that suggests
liquid water on the Early surface of that planet and now, we
know
Quite conclusively, that there was much
more abundant liquid water On the surface on Mars early in its
history. And as we saw earlier in this course,
liquid Water is necessary for life as we know it. So the presence of liquid water on the
early history of Mars, in the early History of Mars suggests that this is a Planet that may have been habitable for
life. This is a remarkable image of Jezero
crater on mars, and You can see an ancient Martian river
flowing out into a crater. And these deposits, that are essentially Deposits of sediments in a delta. This is an ancient lake on the surface of
Mars. Could it have harbored life? Well, this is one of the questions that
we're looking at. But as the space age developed, so
astrobiology has moved into perhaps A more optimistic stage of considering the
possibility of life beyond Earth. What were the other developments that
allowed astrobiology To make the transition from a
philosophical and Speculative science in ancient Greece and
in the Renaissance. To an empirical science constrained by
data. Well, let's have a look at some of these
early developments. And, possibly one of the most important
experiments was One conducted in 1952, when the scientists
Urey and Miller, Who were interested in the origin of life,
and they Carried out an experiment, to simulate an
early Earth atmosphere. And you can see this Rather ingenious apparatus where they've
got some water boiling away inside a Flask, being circulated into another
container That's got an electrical discharge
apparatus. And this electrical discharge is
discharging Across an ancient simulated Earth
atmosphere. And they circulated this water round and
round. And after a period of time, they found That the gases in this container, once
they
Had been electrically sparked, transform
themselves into amino acids, That we saw, are the building blocks of
life. So, in this simple experiment, using only
water and the constituents of Early Earth atmosphere, these scientists
managed To create the building blocks of life. This was a truly remarkable experiment, a
breakthrough in astrobiology that Allowed scientists to go from speculation
about the origin of life, To thinking about how those early building
blocks might well have formed. Nowadays we think that the atmosphere of
early Earth is actually slightly different From the atmosphere that was used by Urey
and Miller in the early experiments. But nevertheless this remains a remarkable
and landmark experiment in The early history of Astrobiology, at
least in the twentieth century. And taking our understanding of the origin
of life to a new, empirical level. Alongside these sorts of studies people
were beginning to study the early rock Record on the Earth, to try and find
evidence for early life on Earth. Collecting rocks, breaking them open, and
trying to see whether there was life. These are some images of ancient
microfossils from the Apex Chert, which is A type of ancient rock found in Australia.
Well over, 3 and a half billion years old. And these are, purportedly, the
microfossils, fossils Of the earliest life forms on Earth. Well, these fossils are highly Controversial, and many scientists argue
about, The nature of different types of fossils
in the rock record. Are they biological? Are they produced by chemical processes? And we'll look in a bit more detail at
that in a future lecture. For these early studies of fossils in the
rock, record were pivotal in Beginning to take, again our understanding
of the early Evolution of life on Earth to a new
scientific level Where we can start to argue about evidence
for fossils In the rock record, an argument that
continues vigorously today. And other experiments were also taking Astrobiology into new territory,
scientific territory. We looked at some of the early evidence
for, the lack of civilizations on Mars.
Well, by the 1970s, we were able to send
spacecraft to the surface of Mars. And the Viking I and II landings which are
shown here, carried out The first biological experiments on the
surface of Mars, to search for life. Their results Were inconclusive and again these are
highly controversial Results that many scientists continue to
argue about today. Did Viking I and II find life or did they
not? Well these, experiments will be backed up
or not supported, as the case may be, by The Mars Science Laboratory and other
rovers and Missions that will travel to Mars in the
future. For the Viking I and II missions to Mars
in the mid 1970s. Again, Were a breakthrough in Astrobiology
because They were the first real experiments, the First empirical experiments to search for
life on the surface of another world. And they took Astrobiology from Early speculations to new experimental
discoveries. Other very interesting experiments
occurring even in the 1970s. The first, signal was sent out to Alien intelligences from the Arecibo Dish
Observatory In Puerto Rico. And you can see the image of the message
that was sent out into space here. It was sent out in binary code, and it
included lots Of information, such as, for example, a
diagram of DNA, the information Storage system of life, a diagram of a
human being, A Map of our solar system and even the
numbers one to ten. Well, this message was very short, and it
probably Will not be picked up by an alien
intelligence, But nevertheless, the first experimental Attempt to communicate with alien
intelligences. A new and remarkable experiment in the Search for and communication with
extraterrestrial intelligence. In very recent times we've seen new
experiments to study the environments Of other planets and see whether they
might be capable of supporting life.
These images sent back by the Mars science
laboratory of Ancient rivers and ancient river beds on Mars conglomerated rocks that have
believed to have Formed By flowing water at the bottom of
rivers on Mars, over 3 billion years ago. Evidence that there was liquid water on
Mars, and Evidence that these are the sorts of
places where We might try and search for evidence of
life, Or at least see whether these environments
were habitable. And beyond Mars in the last Two decades other extraordinary
discoveries that are taking astrobiology Into new realms and new locations to
search for life. This incredible image of Enceladus a tiny
moon of the planet Saturn. And there's evidence that there are
geysers erupting from the south pole of This moon, throwing out water and Other elements into space including
organic carbon. The Cassini spacecraft that flew through
these plumes, discovered different Elements like, silicate, sodium, water,
also methane and complex organic carbon. Is Enceladus a location for life? Well at the moment we don't know, but this
is certainly A very promising target for Astrobiologist
to explore in the future. And might be one of the best places to
study early chemical Reactions, that might've been responsible
for the origin Of life, or even to search for life
itself. Other moons have been discovered that are
covered in interesting chemistry. This is the moon Titan, another moon of
Saturn. The Huygens probe landed on the surface of Titan a few years ago and took these
images. Showing surface of Titan covered in these
rocks. These rocks are actually made of ice, Icy water. But they're in an environment that's very
different from One that you and I may be familiar with. Here, the rivers are made of liquid Methane and other types of hydrocarbons
like ethane.
This an alien world, but an alien world
full Of organic chemistry, which might tell us
something about the Early evolution of life on the Earth and
how Organic chemistry gives rise to the
building blocks for life. This is a promising location for Astrobiologists to understand the
chemistry That's necessary for early pre-biology. And I think it's true to say, and this is
not An exaggeration, but the most Extraordinary development in astrobiology
over the Last two decades, has been the search for
planets around other Stars, and particularly recent searches
for Earth like planets around other stars. This is one of the holy grails, if you
like, Of astrobiology to find a second Earth
orbiting another star. In recent years most of the planets that
have Been discovered are too hot, they're too
close to their Star or they're too large, they're gas
giant planets That don't have rocky surfaces, necessary,
we think, for life. But in the last couple of years, planets Are being discovered around other stars,
the size Of the Earth or slightly larger than the Earth, that may have conditions suitable
for life. The search for Earth-like planets around
other stars is surely One of the most incredible developments in
astrobiology in recent years. And one of the most extraordinary
vindications of that early speculations By Giordano Bruno about the possibility of
numberless Earths orbiting other stars. So what have we learned in this lecture? We've learned that despite everything we
hear about astrobiology Being a new science, it's actually an
ancient science. That began in the philosophical schools of
ancient Greece. It's only recently it's become very Scientifically constrained with new
missions and Spacecraft that have allowed us to study
the surfaces of other planets And new studies of ancient rocks that have
allowed us to study
The possibilities of early life on Earth
and how life first originated on Our planet. We have also learned there are several Planetary bodies in our solar system that
have Become of interest in the search for life
and we'll be explored in future years. We can now hunt for Earth-like planets
around other stars in Our galaxy, opening up vast realms of
space to astrobiologists to Search for life, and study whether the
experiment in biological evolution That has occurred on the Earth, may have
occurred somewhere else. I think we can say without A shadow of doubt, the future will hold
many remarkable Discoveries and surprises in this rapidly
developing field of astrobiology. [BLANK_AUDIO].
