GOALS: Can we define "Life"?
- Can we guess at what Life needs to evolve on a planetary surface?
- What are the chances of life existing, or having existed, on Mars?
- What form might this life take?
- What issues are involved with introducing living things from Earth to Mars?
- Contamination of Mars and back-contamination of Earth. National Park status?
- The Antarctic Treaty?
- The Space Treaty
- Look at the cultural dimension.
PROCEDURE: Imagine that you are travelling around the Universe searching for life. Get a group of your friends together and ask each of them to imagine being a complex creature, a plant, a simple microbe, a rock, a flame, etc, but not to tell you which. "Interview" each of them and . Each person you interrogate has to tell you one thing which will be acceptable to you as a definition of "life". Be careful, because some processes, like breathing, can be duplicated by non-living things [like a car engine]. At the end, list the reasons of the survivors, and compare them to the reasons normally given in text books. Is the difference between living and non-living things as clear as you first thought?
Find out about the surface conditions of Mars. In what way are they similar to Earth, and how are they different? What effect might the differences have on the chances of life existing on Mars?
If you were a Martian, and you looked at the Earth, do you think you would believe that there was life there? What might make you think that the Earth was unsuitable for life as you know it?
Examine Viking and Mars Global Surveyor photos of Mars. What evidence can you see that suggests that Mars was a very different place billions of years ago? Was it similar to the Earth? List the effects that flowing/standing water has on the surface of the Earth. Can you see any similar features on Mars? Can you think of any explanations for the lack of flowing water on Mars now?
Picture yourself standing on Mars: you have no spacesuit, but for now this doesn't matter. Look around you. What do you see? What do you hear - remember the atmosphere is very dry, thin and cold. How would this affect what you could hear? What is missing? Discuss how you would feel when you think back to the Earth. Perhaps you could express this best in a picture, a photo, a computer image; possibly you could write a poem, or compose a piece of music. How does it feel to be totally alone on a dead, red world?
Life seems to have begun on Earth very soon after it formed, about 4, 000 million years ago. Earth and Mars might have been very similar when they formed. The conditions on the Earth were very hostile to life as we think we understand it now. But recently we have discovered what are known as "extremophile" bacteria, living in very hostile conditions - boiling water, radioactive waste, high pressure, total darkness, inside rocks and at great depths in the Earth.
What does the word "extremophile" mean? Find out the meaning of the words "halophilic", "thermophilic" and "barophilic". When the Viking probes went to Mars, these organisms weren't known about, and so their detectors wouldn't have been able to find them. If Viking went to Mars now, the story might be different.
If you were given the job of searching for life on Mars, what would you base your ideas on? What evidence would you look for? Remember that living things interact with and change their environments, and are changed by their environemnts. What visual evidence might you look for? If you were to take a photograph of your local area, what things would indicate that life was [or was not] evident? How would you persuade your colleagues?
The life detection experiments on board Viking used the same basic idea: take a sample of Martian soil, expose it to a "soup" of nutrients that Martian bacteria might like, and see what happens. Then burn the soil to free any organic molecules and radioactively-tagged carbon 14. You could try the "Mars Jars" experiment in module 3. You can also try the idea of burning soil to see if you can find any organic residues.
If life is as tough as it seems to be, then we face a problem when we send probes to Mars. What problems do you think these might be, and how might they affect our results? How could we make sure that we have 100% sterilised the probe? What methods do we use to sterilise areas around our homes, and are there certain dangers in some of the methods we use?
If an organism from Earth did survive the journey to Mars, do you think it would spread? One day, we hope to achieve a sample return mission, with a probe sending back samples of Mars rock. Do you think a Martian microbe could infect Earth organisms? How many diseases can be caught by both humans and animals? Would we be sensitive to a Martian microbe, or would it be so different that it would have no effect on us? What steps do you think we should take to ensure that any possible Martian organisms don't contaminate Earth?
Some people think that there is no life on Mars, and that we should eventually turn Mars into another Earth, through a procerss called "terraforming". Do you think the same, or do you think that what makes Mars so interesting is that it is so different? If you had the power, how would you protect the Martian environment? Would you make it into a sort of "National Park", or would you treat it in the same way as Antarctica is at present? To answer this, you will need to find out about the Antarctic Treaty.
Do you think that the discovery of life on Mars, or anywhere else in the Solar System, would change things down here on Earth?
How does your Garden Grow?
Try growing different types of seeds in the Martian-type soil that can be created using the recipe at . We suggest broad beans, cress, poppies and grass. Grow some of the same seeds in a tray of your local soil and monitor which grow best, under different environmental conditions.
Try growing plants in your CO2 chamber. How do they compare with plants grown in the air.
Also light and dark
Germination needs: water, temperature, oxygen, light
What are your conclusions about your Martian soil.
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