Life—The Final Frontier
A Case Study on the Characteristics of Life
by
William Rogers, Ball State University
Thomas Horvath, SUNY-Oneonta
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CQ1: Do you think life exists elsewhere
in the universe besides planet Earth?
A: Yes
B: No
Photo courtesy of http://hubblesite.org/
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The Scenario
The President of the United States is under
extreme pressure from the public and
Congress to find ways to balance the budget.
Space exploration is one area frequently
mentioned for budget cuts.
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The Scenario Continued…
However, the President is fully aware that
there is a risk, albeit small, that if life forms
from space enter the Earth’s biosphere, the
ecological and/or pathological consequences
could be severe.
Because of this, the President does not want
to cut funding for the space program.
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Your Task
Your job, as a chief advisor to the President,
is to make a recommendation based on the
following study. The President wants to know
if an announcement should be made that
extraterrestrial life has been discovered.
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Planetary Protection
ALL OF THE PLANETS, ALL OF THE TIME
NASA has a Planetary Protection Policy that is designed to
protect planets, moons, asteroids, etc., from contamination
by Earth life, and protecting Earth from possible life forms
from other solar system bodies. The Policy protects planets
from living organisms, not fossil or chemical evidence of
life.
One of NASA’s goals is to determine the characteristics of
living organisms.[1]
How will NASA determine if what it finds is evidence of life
or is something that is actually alive?
1 http://exobiology.nasa.gov/ssx/exobiology.html
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So what are the basic
characteristics of life?
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Are any of these alive?
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Do they exhibit
characteristics of life?
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CQ2: Why do space programs like
NASA look for evidence of water on
Mars?
A: Martian life requires water.
B: The polarity of water is necessary for making
DNA.
C: Earth life requires water.
D: Organic molecules can be dissolved in water.
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Planetary Protection
ALL OF THE PLANETS, ALL OF THE TIME
The NASA Planetary Protection Team has been
given a chunk of subterranean ice collected on
Mars by one of the rovers.
The first task is to determine if the ice contains
evidence of life.
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Planetary Protection
ALL OF THE PLANETS, ALL OF THE TIME
Initial scans of the ice
reveal bacteria-like
nanoparticles (100 nm
or smaller) that contain
DNA.
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CQ3: How do you determine if the
nanoparticles are alive?
A: Thaw the ice and see if they are
mobile.
B: Thaw the ice and see if they grow
and reproduce.
C: Keep it frozen and run tests to
determine more about their
chemical composition.
D: Thaw the ice and expose them to
an electrical charge and look for a
response.
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Results from Nanoparticle Scans
• Surrounded by cellular membrane
– Composed of calcium phosphate rather than
phospholipids
• No internal membrane-bound structures
(organelles)
• Not mobile
• Small amounts of DNA and proteins
• Reproduction only in anoxic environment
– Antibiotics prevent reproduction
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CQ4: Based on the class list, is there
enough evidence to say that the
nanoparticles are alive?
A: Yes
B: No
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Planetary Protection
ALL OF THE PLANETS, ALL OF THE TIME
Closer investigations
reveal viruses
attached to some
nanoparticles
Image Courtesy of the National Science Foundation
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Virus – Structure and Replication
Many good figures showing viral structure and
reproduction/life cycle are available online and in
textbooks.
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Results from Virus Scans
• Contain RNA and proteins.
• Not mobile.
• Only reproduce when nanoparticles
are present.
• Don’t use any type of food presented
them.
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CQ5: Based on the class list, is there
enough evidence to say the virus
objects are alive?
A: Yes
B: No
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CQ6: Will you confirm to the President
that extra-terrestrial life has been
discovered?
A: Yes
B: No
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Why or why not?
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