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Life—The Final FrontierA Case Study on the Characteristics of Life

by

William Rogers, Ball State UniversityThomas 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 ScenarioThe 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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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

Planetary ProtectionPlanetary ProtectionALL OF THE PLANETS, ALL OF THE TIMEALL OF THE PLANETS, ALL OF THE TIME

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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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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.

Planetary ProtectionPlanetary ProtectionALL OF THE PLANETS, ALL OF THE TIMEALL OF THE PLANETS, ALL OF THE TIME

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Initial scans of the ice reveal bacteria-like nanoparticles (100 nm or smaller) that contain DNA.

Planetary ProtectionPlanetary ProtectionALL OF THE PLANETS, ALL OF THE TIMEALL OF THE PLANETS, ALL OF THE TIME

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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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Image Courtesy of the National Science Foundation

Closer investigations reveal viruses attached to some nanoparticles

Planetary ProtectionPlanetary ProtectionALL OF THE PLANETS, ALL OF THE TIMEALL OF THE PLANETS, ALL OF THE TIME

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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?