Astrobiology in the Classroom


NASA – CERES Project –

Montana State University

Preliminary Edition




“Microbial Zoo”









In this activity, students will explore the extreme conditions life is known to exist in on our own planet.  They will see that life can exist in a variety of environments, broadening the prospects for life to exist elsewhere in the universe.  As humankind begins to look for life among the stars, it is critical to understand the variety of conditions in which microbial life is found, so that it will be easier to identify other worlds where it might exist.  These activities involve students in broadening their criteria for life by examining those extreme environments on Earth, then looking at how those lifeforms could exist on other known worlds within our solar system.


Part I – Exploration:


Living in a Microbial Zoo


  1. Describe an environment on Earth that would not allow any form of life to exist.  List specific examples, and explain why these environments cannot support life.







  1. Circle areas on the map of the world below that correspond to places on the Earth having conditions that prohibit life. 

















  1. Get together with a partner.  Compare and discuss your responses to the previous questions.  Answering questions A and B below.  Then use a different colored pencil or pen to note any changes you would make in questions 1 or 2.


    1.  Are there any of your partners’ examples you would like to add to your own, or vice versa? 




    1. Are there any that you would like to eliminate from your list? 


  1. After surveying a large number of college and high school aged students, it was discovered that the three most common environments listed as being unable to support life were (1) environments in which there is no oxygen, (2) environments of extreme temperature (too hot/too cold), and (3) environments without access to water. 


    1.  Did you or your partner include any of these environments? 




    1. If you didn’t, do you feel that you should have?  Explain why or why not.








  1. Scientists are currently searching for life on other planets and moons both inside and outside our solar system.  What types of life form do you think they are most likely to find (1) animals, (2) plants or (3) microorganisms?  Explain your reasoning.






Part II – Concept Introduction:


With the growing interest and of the new multi-disciplinary science of astrobiology, there has been an increase in funding for research projects investigating life forms living in extreme environments on Earth.  The term extreme environment is meant to describe any environment that is extreme with respect to humans.  As a result of this research, we are finding that life exists in virtually every environment on Earth.  However, most of this life is in the form of microorganisms.  Microbes that thrive in extreme environments are lumped together under the generic name of extremophiles.  Extremophiles can be further classified according to the environments in which they live.  Examples of specific extremophiles are thermophiles, psychrophiles, acidophiles, alkalophiles, barophiles, xerophiles, halophiles, and anaerobes.  Your teacher will now show you a Power point slide show introducing you to these microorganisms.  Get a blank chart of extremophiles to help you take notes during the presentation.



  1.  Now that you have seen the presentation, refer back to the environments listed in problem 4.


Do you think that any of these environments actually present conditions too extreme for life to exist?






  1. Based on your responses to problem 6, what is the one environmental condition that all life needs to survive on Earth?





Part III – Concept Application:


1.  You will now receive a data sheet listing some extreme environments in our solar system.  What is it about each of these environments that makes them extreme?


    1. Mars



    1. Venus



    1. Europa



    1. Titan



    1. Io



2.  If you were searching for life on the planets/moons listed on your data sheet, what types of extremophiles might you find?  Explain your reasoning.


    1. Mars



    1. Venus



    1. Europa



    1. Titan



    1. Io



  1. Which planet/moon do you feel is most likely or able to support life?  Explain your reasoning in detail.











































































More Extreme Environments


For comparisons sake:

Earth atmosphere: 78% nitrogen, 21% oxygen, 1% argon, and 0.03% carbon dioxide

Earth temperature: 288K    


-thin and unbreathable atmosphere

-atmosphere contains 95% carbon dioxide, 3% nitrogen, 1.5% argon, trace amounts of water, and no oxygen or ozone

-temperatures range from –125oC to 25oC (223K)

-some rocks are basalt (volcanic lava, as in Hawaii)

-polar ice caps made of CO2 ice with possible water ice beneath


-extremely high atmospheric pressure

-atmosphere contains 96.5% carbon dioxide, 3.5% nitrogen

            -little to no water

            -sulfuric acid rain

            -mean surface temperature of 740 K (daytime and nighttime)

Europa (moon of Jupiter)

            -icy surface

-possible water oceans beneath icy crust

-subject to partial melting due to tidal forces from Jupiter



Titan (moon of Saturn)

-thick atmosphere is ~90% nitrogen

-instead of oxygen (like Earth) the atmosphere contains methane, ethane, argon, and hydrogen compounds

-surface temperature of 93 K (-180oC)

-composed mainly of methane and ammonia ice

            -possible ethane oceans

Io (moon of Jupiter)

            - average is about 130 K (-143 oC

-active volcanism

            -sulfur dioxide atmosphere

            -boiling sulfur and sulfur dioxide geysers with temps as high as 2000 K (1723 oC)


Triton (moon of Neptune)

-surface composed of a mixture of ices of nitrogen, methane, carbon dioxide, and carbon monoxide surrounded by a thin atmosphere

-surface temperature of 40 K (-235oC)