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Astrobiology And the Search for Extra Terrestrial Life
The University of Edinburgh
Lecture Summary: The Introduction and History of Astrobiology

The Introduction to Astrobiology
Are we alone in the Universe?

Astrobiology is concerned with:
-

The origin and evolution of life on Earth
The possibility of life on other planets
The limits of life on Earth

In order to understand the past history of life on Earth, we need to understand the cosmic
environmental connection as well as the limits of life on Earth
Questions to consider when addressing the topic on the limits of life:
How far can life be pushed?
What are the most extreme chemical and physical environments that life can grow
and survive in?
How does life evolve?
What sorts of mechanisms evolve?
How does the biochemistry evolve?
What kind of physiology do organisms evolve?
Are these limits universal?

The History of Astrobiology
-

The space age began to unfold in the 1950s and early 1960s
People began to see valley networks and channels on the surface of Mars
→ Outflow channels suggest the possibility of liquid water on the early surface of
the planet which led to speculation that it may have been a habitable planet

Looking for civilizations and other life forms

The 1970s
-

Viking I and Viking II landed on Mars and did the first biological experiments on the
surface of Mars
The results were inconclusive, which led to much controversy
Arecibo Dish Observatory in Puerto Rico sent out the first signal to alien intelligence in
binary code:
→ Diagram of our DNA
→ Diagram of the human body
→ A map of our solar system
→ The numbers 1 to 10

In more recent times
-

-

Mars Science Laboratory conducted experiments to study the environments of other
planets and their capability to support life
→ It sent back images of ancient rivers, ancient river beds and conglomerated
rocks believed to have formed by flowing water at the bottom of rivers on Mars,
over 3 billion years ago
The most extraordinary development in Astrobiology over the past two decades has
been the search for planets around other stars, particularly for Earth-like planets
The drawbacks of the planets that have been discovered:
→
→
→
→

Too hot
Too large
Too close to their parent star
they’re giant gas planets that don’t have the necessary surfaces suitable for life

The Influential Men of Astrobiology
Metrodorus
-

Student of Democritus
He said that it’d be strange if a single ear of corn grew in a large plain, although there’s
only one habitable world in the infinite
→ The idea is 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

So, he wondered the same about life; if there is life on this planet then surely there must be
other worlds with life as well
...


Discoveries
The Moon Enceladus of Saturn
-

Evidence of geysers erupting from the South Pole, throwing out water and other
elements into space:
→ Silicate
→ Sodium
→ Methane
→ Complex organic carbon
→ Water

The Moon Titan of Saturn
-

by Cassini Spacecraft

by Huygens Probe

Found it to be covered in ‘rocks’ made of ice and icy water
Found rivers made of liquid methane and hydrocarbon ethane



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