Life on Mars

Astronomy, Biology:	Astrobiology
Grade Range:	High School
Format:	Stage

This demonstration is a creative way to look at how we search for extraterrestrial life.

Materials

• "Martian Soil" Samples:
  • Food Dye
  • Yeast
  • Sand
  • Sugar
  • Salt
  • Dirt
• Water
• Three Culture Tubes
• Three Balloons
• Hot Plate
• 600mL Beaker

Safety Precautions

Please read the General Safety Precautions section of the Demonstration Safety page before performing this demonstration.

Demonstration

Preparation: Making the "Martian Soil" Samples:

1. Mix the sand and dirt in a large bowl. Add a small amount of red food dye and mix thoroughly to turn the "Martian soil" red. separate the mix into three equal sized piles and set aside to dry.
2. Make three piles of sugar, one larger and two smaller. and add yellow food dye to each pile. Mix thoroughly and set them aside to dry.
3. Make a small pile of salt and add blue food dye. Mix thoroughly and set aside to dry.
4. Once the piles have all dried, separate the salt into two larger piles and one smaller pile. Mix the small salt pile with the large sugar pile and a soil pile, then store and label it as "Sample A". Mix the remaining piles accordingly and label them "Sample B" and "Sample C".
5. Add some yeast to sample A, half as much in Sample B, and none in Sample C. Mix it in, and keep the containers stored in a cool, dry space to avoid accidentally activating the yeast.

Presentation

1. 10-15 minutes before presenting, fill each test tube halfway with their respective samples. Add enough water into each test tube to cover the soil mixtures, and gently mix them to ensure all the soil is wet. Put a balloon on top of each test tube, and place them inside the beaker. fill the beaker 2/3 with water, and place it on the hot plate set to low-medium heat (2-3). Keep the hot plate off to the side until needed.
2. Show the audience the bottles with samples, and explain that the samples are similar to what we might find on the martian surface: They have some soil, some sand, some basic compounds (salt) and some complex compounds (sugar).
3. Ask the audience if they know how we might check for past life on Mars. Answers might range from our search for water, to checking for organic compounds, to testing soil samples.
4. Expand on the idea of testing soil samples. Explain that one way we are testing the soil samples is similar to how we show that yeast is alive; by gently warming it, adding water, and seeing if anything such as CO₂ comes out to show respiration.
5. Pull out the hot plate with the samples. By this point, Sample A should have some CO₂ trapped, while Samples B will be mostly limp and Sample C will have nothing. Explain that the type of soil sample can determine the kind of result we find.

Why This Works

One of the biggest questions about our universe is "Is there life on other planets?" Our neighboring planet Mars could have had life on it at one point, which is why we have different kinds of probes and rovers on the planet to investigate. The first thing that we have them checking is the soil on Mars, to see if it could support life and had the necessary components to do so. Sample A could support life, because it has some simple organic compounds in it that an organism could break down, and it has a low salt concentration which allows organisms to grow. Samples B and C, however, have much higher salt concentrations. The high levels of salt make it hard for organisms to survive in this soil, so it wouldn't be an ideal soil to check for evidence of life. We then took our samples and added some water to them, as well as low heat to encourage any microorganisms to wake up. Sample A had some yeast added, had plenty of sugar, and it also had a low concentration of salt, so the balloon inflates as the yeast creates CO₂. This means Sample A came from an area that was very hospitable to life, and would be a great place to keep looking for more samples. Sample B might inflate a little, since it also had some yeast, but it also had a much higher level of salt in it. The high levels of salt make it hard for the yeast to survive, so although we might see the balloon inflate a little, we know that this sample is from an area that wasn't very hospitable. Sample C had no yeast in it, so it doesn't inflate at all. This tells us that the area Sample C was taken from couldn't support life, and so we need to look elsewhere.

Almost all the water on Mars is frozen, making it impossible for organisms to try and survive on the current surface. Not only that, but the surface of Mars is really hot in the day and very cold at night, due to the thin atmosphere. For a planet to be hospitable, it has to have conditions similar to what we have on earth: a good atmosphere, water, and hospitable temperatures. There is evidence that Mars used to have a good atmosphere, and with that it used to have liquid water. This is why we are checking to see if Mars used to have life on it, and if we could make Mars hospitable again.

Additional Information

• This demonstration pairs well with the Chlorine The Bacteria Killer
• This demonstration is a part of the Astronomy Show