Transcript Alien Earths Floorplan (3,000 sq. ft) Major Exhibit Areas

The
Traveling Exhibit
Science Background
Part D: Search for Life
prepared by Dr. Cherilynn Morrow for the Space Science Institute
Boulder, CO
D. Search for Life
KEY QUESTIONS:
Does life exist on an extra-solar planet? How can we
find it?
NASA’s Terrestrial
Planet Finder
The SETI Allen
Telescope Array
The search for life beyond Earth is
informed by what we know about life on Earth.
Life as we know it requires:
1. liquid water;
2. some form of energy (e.g. sunlight, chemical, volcanic);
3. access to organic materials (e.g. carbon compounds);
4. a sufficiently stable environment (i.e. time to originate and evolve).
On planet Earth life has evolved.

Courtesy NASA’s Navigator Program
15
We’ve discovered that
microbes are vital to every
other living thing on Earth!
Alien Earths:
Weighing Life
Interactive
Cool!
Most of the life on Earth is microbes, not animals or plants!
Animals and humans make up only 1% of the life on Earth.
Humans could not survive without microbes!
Why Search for Life Beyond Earth?
In the past couple of decades, the study of
life on Earth has revealed the existence of
life in “extreme” environments that were
generally thought to be uninhabitable.
Tube worms near
deep ocean
hydrothermal vent
The organic chemicals needed for life as we
know it are found pervasively in and
between the stars of the galaxy.
In the past decade we have been detecting
more and more planets orbiting other stars.
It is a compelling question whether we are
alone or other life (especially self-aware
life) is out there. Either answer is amazing!
Star forming
region
Artist concept
Sun-like star with
Earth-like planet
Searching for Signs of Life Beyond Earth
What are scientists doing?
1. Astrobiology: Studying life on Earth to aid
the search for life beyond Earth —
microbial life in “extreme environments”
Artist concept
Mars rover
2. Planetary Exploration: Exploring planets in
our solar system with robots — Mars rovers
seeking signs of past surface water
3. Finding Extra-solar planets: Searching for
Earth-like planets orbiting distant stars—
NASA’s Kepler Mission.
Kepler
Artist
concept
4. Looking for Signs of Life: Learning how to
measure the composition of the
atmospheres of extra-solar planets to
detect signs of life.
5. SETI: Seeking electromagnetic signals
from a technological civilization
Parkes Radio
Telescope
Life Changes its Environment
 Life needs a suitable environment to
flourish. It also feeds back and changes
its environment.
 The way life changes its environment
is known as a biosignature – a sign of the
presence of life.
 Oxygen in Earth’s atmosphere is a
Note the presence of ozone (O3), and
water vapor in the spectrum of Earth’s
atmosphere – indirect evidence of life!
biosignature of life. Looking from afar,
we cannot see plants and bacteria
directly, but we can infer the presence of
photosynthetic life if there is
atmospheric oxygen.
Life Changes its Environment
Microbial Mats
Microbial mats are complex
colonies of different types of
microbes. When exposed to
light they emit gases that
over time can transform the
composition of a planetary
atmosphere.
There is a microbial mat in
the Alien Earths exhibit.
“Hollywood Alien”
Cyanobacteria like the one below
may represent a more likely type
of alien whose presence might be
detected via its transformative
effect on the atmosphere of an
extra-solar planet.
How will we know a planet supports life?
Look for evidence
of oxygen
Analyze the
reflected light from
the planet to see if
the planet has an
atmosphere
Look for liquid
water
Look for signs of
biological activity
(methane)
and rule out other explanations.
Courtesy NASA’s Navigator Program
17
NASA’s Terrestrial Planet Finder
Does life exist on an extra-solar planet? How can we
find it?
In a decade or so, TPF's
spectroscopy should allow
atmospheric chemists and
biologists to use the
relative amounts of gases
like carbon dioxide, water
vapor, ozone & methane to
find whether an extra-solar
planet may support life.
Artist Conception of NASA’s
Terrestrial Planet Finder (TPF) spacecraft
The SETI Search
The SETI Institute uses radio and optical
telescopes to search for signals that
might be emitted by technologically
advanced life.
Parkes Radio
Telescope
The Allen Telescope Array is being
developed at Hat Creek, CA to greatly
expand the SETI search.
Allen
Telescope
Array Dish
The Drake Equation
What do we need to know about to discover life in the galaxy?
N = R* fp ne fl fi fc L
N = estimated number of civilizations in the Milky Way Galaxy
whose electromagnetic emissions are detectable.
R* = rate of formation of stars suitable for the development of intelligent life.
fp = fraction of those stars with planetary systems.
LOTS OF THINGS!
ne = number of planets, per solar system, with an environment suitable for life.
fl
= fraction of suitable planets on which life actually appears.
fi = fraction of life bearing planets on which intelligent life emerges.
fc = fraction of civilizations that develop a technology that releases detectable
signs of their existence into space.
L = length of time such civilizations release detectable signals into space.
The Drake Equation
N = R* fp ne fl fi fc L
The Alien Earths exhibit has
a computer kiosk where you
can play with the numbers
of the Drake Equation!
Our Milky Way galaxy may
look like this one. It is home
to more than100 billion stars!
N
= estimated number of civilizations in the Milky Way Galaxy
whose electromagnetic emissions are detectable.
N = R* fp ne fl fi fc L
R* = rate of formation of stars suitable fp = fraction of those stars with planets
for the development of intelligent life.
N = R* fp ne fl fi fc L
ne = number of planets,
per solar system, with an
environment suitable for life.
fl = fraction of suitable planets
on which life actually appears.
N = R* fp ne fl fi fc L
fi = fraction of life-bearing planets
on which intelligent life emerges
(may not be life with technology)
fc = fraction of civilizations that
develop a technology that releases
detectable signs of their existence
into space.
N = R* fp ne fl fi fc L
N≈L
L = length of time such civilizations
release detectable signals into space.
Alien Earths:
SETI
Interactive
Me too!
“I’m detecting different
kinds of spacey signals!”
A future SETI
scientist ?
A current SETI scientist
Now the challenge is to
discern whether any of these
signals could be signs of a
technologically advanced,
extraterrestrial civilization.
D. Search for Life
SUMMARY
The search for life beyond Earth is shaped by what we know
about life on Earth.
Life on Earth requires liquid water, energy, organic
materials. Most life on Earth is microbial.
Life changes its physical environment in ways that are more
easily detected from afar than the life forms themselves.
Knowledge of these changes determines
how we look for life elsewhere (e.g. oxygen in a planetary
atmosphere or radio signals from technological beings).
The “Origins” Timeline in Pictures
(As best we currently know it)
Can you trace the symbolic steps from the Big Bang to life?
Heavier elements needed for life created in massive stars
and spewed into the galaxy via supernova explosions
Sun & planets
forming
BIG BANG
Organic
materials
Habitable
worlds
LIFE!
CONCLUSION
Re-visiting the Big Ideas of the Introductory Presentation
We are developing
extraordinary new tools,
techniques, & insights for
exploring the age-old
question of whether there is
life beyond Earth.
Our search for habitable
worlds and signs of life in our
galaxy is guided by our study
of how stars and planets
form & our understanding of
life on Earth.
Parting Points to Ponder
The natural processes in
our universe have resulted
in life forms (e.g. humans)
capable of reflecting on
their own origins and on the
possibility of life elsewhere.
There are two possibilities:
Maybe we’re alone…
Maybe we’re not…
Both are equally amazing…
We shall not cease from exploring,
And the end of all our exploration
Will be to arrive where we started
And to know the place for the first time.
- T.S. Eliot, Little Gidding