Extraterrestrial Life

Problems/Case Studies

Is a Mars Sample Return Mission Too Risky? 
Troy D. Wood, University at Buffalo
Following a public hearing format, this case study allows students to explore the scientific and public policy issues surrounding the advisability of a return mission to Mars for further sampling and, more generally, the question of whether or not there is life on that planet. The case was developed for a non-science majors course called "Great Discoveries in Science" and serves to illustrate the scientific method and the importance of interdisciplinary efforts in scientific research.
Appropriate for high school astronomy classes, and college undergraduate general science courses.

How Does Silex Strobilus Replicate? D. E. Allen.  Thinking Toward Solutions:  Problem-Based Learning Activities for General Biology.  Allen, D. E. and Duch, B. J. (1998).   New YorkSaunders College Publishing. A hypothetical newly discovered organism.  Students investigate replication, the definition of life (it is not carbon-based), and the structure of its DNA.

Are We Alone in the Universe?  The Search for Life on Other PlanetsAn interactive problem which explores the implications of discovering extremophiles and nanobes on the search for life on other planets.  The problem helps students uses what they learn about characteristics of life on earth, and these recent discoveries, to re-conceptualize what they're understand about the very nature of life on earth.
Supporting Materials:


On file in PBL resource cabinet

Topic:  "Plants to Mars":  Biology 6th Ed. CNN Ed 2002 (2:01)

NASA scientists are planning to send genetically engineered plants (Arabidopsis) on an unmanned mission to Mars in 2007. The plants will be grown in Martian soil and will be engineered to contain foreign genes. For example, the plants will contain a gene for a jellyfish protein and will glow green when stressed. Observation of these reporter plants by camera will allow scientists to evaluate how they respond to Martian conditions.

Online Videos

"Mars, Dead or Alive", NOVA Video 

This hour-long program is divided into seven chapters. Choose any chapter below and select QuickTime, RealVideo, or Windows Media Player to begin viewing.
Chapter 1 - A Hostile Environment
Chapter 2 -  High Stakes
Chapter 3- Unexpected Problems
Chapter 4- Where to land?
Chapter 5- Engineers Prevail
Chapter 6- Time to fly
Chapter 7- Postcards from Mars

"Origins", NOVA Video
One hour long program divided into chapters with the quest of reviewing the big bang and putting the early universe into perspective.  Scientists discuss how the building blocks of life were put together in Chapter 5 Forging the elements.  In Chapter 6 astronomers analyze light spectrum from other galaxies to determine if life is possible there.
Chapter 1 - Discovering the Big Bang
Chapter 2 - A 30 year search
Chapter 3 - Race for a sharper image
Chapter 4 - The picture emerges
Chapter 5 - Forging the elements
Chapter 6 - A universe hospitable to life

"The Mysterious Life of Caves" NOVA. WGBH Boston. PBS video. 2002. (60 min)
 The video documents how prokaryote extremophiles survive deep underground in caves under conditions that are inhospitable to most other forms of life, and discusses their role in cave formation.  The video helps students understand that life can exist in a variety of different environments, and encourages them to reconsider the conditions necessary for life.  It ends with a connection to possible life on other planets.

Caves Part I
Caves Part II
Caves Part III
Caves Part IV
Caves Part V

Hydrothermal vent 1

Hydrothermal vent 2


Scientist:  We found life on Mars -and killed it.  Borenstein, Seth.   Post and Courier.  January 8, 2007. 
Thirty years ago, two NASA space probes visited Mars.  One scientist asserts that in 1976-77, NASA was looking for the wrong type of life with the Viking space probes.  Viking probes were looking for life in which salt-water was the internal fluid of life.  On Mars, the internal fluid may be a mixture of water and hydrogen peroxide, which stays liquid at low temperatures.  The Viking crafts would have killed the life by drowning and overheating it during an experiment in which water was poured on soil.  Another experiment heated the soil.  Earth has an organism that uses the water-hydrogen peroxide mixture to its advantage, the bombardier beetle.  A new NASA mission called Phoenix will launch in summer 2007.
What is Life and How do we Search for it? 
C.P. McCay. PLoS Biology | www.plosbiology.org, September 2004 | Volume 2 | Issue 9

Life on Mars." Michael Caplinger, Malin Space Science Systems
April 1995
The site offers background to the Viking biology experiment and samples of the data reported.  The site reports information on extinct life and conclusions able to be reached.

Mars Sample Return:  Issues and recommendations. Commission on Physical Sciences, Mathematics, and Applications1997.   National Associated Press
The site offers excerpts from the book from the 1997 Mars Mission.  The recommendations for the task group on issues in sample return of the Space Studies Board reference the possibility of life on Mars, the significance of Martian meteorites, the possibility of large-scale effects, scientific investigations that may reduce uncertainty and how to evaluate the returned samples. 

Recent results from the Viking labeled release experiment on Mars.
Levin, GV and Straat, PA. Journal of Geophysical Research Vol. 82, Sept 30, 1977.
Additional results have recently been obtained from the Labeled Release (LR) life detection experiment on Mars. On Viking Lander 2 an experiment using surface material obtained from under a rock shows a response essentially identical with those obtained from other surface samples. Further, after a second nutrient injection, there is an initial drop in the level of radioactive gas present in the test cell, followed by a slow, gradual evolution of radioactivity over the long incubation period. This gas evolution, which proceeds at a rate declining with time, attains a final level similar to that seen just prior to second injection. Following completion of this experimental cycle a fresh Martian surface sample was heat sterilized for 3 hours at 46º C prior to nutrient injection. The resultant evolution of radioactive gas is substantially reduced in agreement with results reported previously. These results are consistent with a biological response and also greatly narrow the number of possible chemical reactants. The current status of the Labeled Release experiment on Mars is summarized.

Mars Channels and ValleysMike Caplinger, Malin Space Science Systems February 1995
The site offers an overview with images of the surface of Mars, its atmosphere, and how water features could have been formed on the planet. 

On the question of the meteorite. Lunar and Planetary Institute, 1996.
A team of scientists recently announced that they believe they have found evidence for ancient microbacterial life in a chunk of meteorite that came from the planet Mars. The startling news would be the first discovery of any form of life off the Earth. It could revolutionize our thoughts on the probability of life arising elsewhere in our solar system and the universe beyond, especially in the light of recent news about planet-like bodies detected around other stars.
As with many groundbreaking discoveries, the initial evidence raises more questions than it answers. We have compiled this Web resource to answer some basic questions about Mars and its meteorites and to encourage further questions, discussions, and research on such a vital topic. It contains many links to other information on the Web and in print.

Debate on Mars life rages long after VikingStenger, R.  CNN.com, July 20, 2001
"The mightiest probe ever to land on another planet settled down on Mars on this day 25 years ago, igniting a scientific firestorm that still rages today -- Does the red planet possess life? Officially, NASA concluded that the Viking 1 and its sister ship the Viking 2, which landed on the other side of the planet weeks later, did not uncover signs of life after scooping, baking and dissecting the iron-rich soil. But a handful of scientists, including some who designed the Viking life experiments, maintain that the test results came back positive. "

Mars exploration rover mission:  Hematite".  NASA Jet Propulsion Laboratory,  California Institute of Technology.
"On Earth, the shiny grey mineral has been used to make jewelry for hundreds of years. On Mars, grey hematite may help prove whether large amounts of liquid water ever flowed on Mars' surface. Where water was, life may have had a chance to thrive as well."

Mars Rover multimedia:  Spirit NASA Jet Propulsion Laboratory, California Institute of Technology.
The site offers images of the Mars Rover and the Spirit on their journey to Mars.  

Spirit press release images.  NASA Jet Propulsion Laboratory, California Institute of Technology. 
Spirit's winter panorama of labeled images is featured. 

Mars research:   The Viking Labeled Release Life Detection Experiment
Spherix, 2002.
"In 1997, Biospherics' President and CEO, Dr. Gilbert V. Levin, announced his new conclusion that his 1976 Viking Labeled Release (LR) life detection experiment found living microorganisms in the soil of Mars.Objective application of the scientific process to 21 years of continued research and to new developments on Mars and Earth forced this conclusion. Of all the many hypotheses offered over the years to explain the LR Mars results, the only possibility fitting all the relevant data is that microbial life exists in the top layer of the Martian surface."  The site offers links to articles addressing the topic of life on Mars.

Internet Resources

Hubble Site -
The site offers news, teaching resources, images, and many other resources related to the Hubble telescope and related missions.

Rover mission.  NASA Jet propulsion laboratory, California Institute of Technology
The link offers updated slide shows during specific time periods evaluating the location and events of the Rover mission.

2001 Mars Odyssey. NASA Jet propulsion laboratory, California Institute of Technology
The site offers orbiter updates of the 2001 Mars Odyssey mission.  Problems that NASA will face with communication, the ice beneath Mars, and images from the spacecraft are included in the site.

Mars exploration press release images:  Spirit.  NASA Jet Propulsion Laboratory, California Institute of Technology.
Images include those of the soil analysis, x-ray vision, elemental and mineral analyses, and the technology used for experimentation on Mars.