Life on Mars - Logistics

Time
10 min introduction
20-30 min design experiments
35-50 min conduct experiments (some tests may need to be left overnight)
20-30 min discuss experiments

Grouping
Groups of 2-3 students

Materials
For all tests:

• A copy of the Testing Martian Soils handout for each student
• permanent markers
• masking tape or labeling tape
• hand lenses

For soil samples, enough for a class of 30 students in teams of 3:

• 30 ziplock bags
• 3 cups clean playground sand (no organic material should be present so carefully strain or wash the sand if necessary)
• 8 packages fast-acting yeast (2 ounces total)
• 4 Alkaseltzer® tablets, crushed

For nutrient milkshake:

• 500 ml distilled water
• 85 g table sugar (around 6 tablespoons)
• 85 g all purpose white flour (around 6 tablespoons)
• 1 liter bottle or flask

For agar plates (see Life Trap activity for ordering information):

• 50 sterile disposable plastic 15 mm x 100 mm Petri dishes
• 15 g agar agar powder
• 2 beef bouillon cubes
• 40 g table sugar (around 3 tablespoons) ** Unlike the plates made for the Life Trap activity, sugar is required for agar plates that yeast will happily grow on. If your agar agar powder is pre-sweetened, then no additional sugar is necessary. **
• 1 liter distilled water
• stove and large pot for preparing nutrient agar and steam sterilizing the Q tips
• Q tips
• paper towels
• bleach

For organic molecules tests (see Testing for Life activity for ordering information):

• Copy of test station directions at each test station (see Testing for Life activity)
• Biuret solution
• Benedict’s solution
• Iodine tincture
• beakers or cups
• test tubes
• test tube racks
• eye droppers
• trays or bins to keep the materials for each test station
• small 100 ml beakers or squeeze bottles to contain test reagents
• Optional: large squeeze bottles of water (500 ml disposable plastic water bottles are fine) for rinsing test tubes at test stations rather than going to a sink
• large beakers or cups to dump waste materials
• hot plate or source of boiling water
• insulated containers such as a thermos or Styrofoam cup for creating a hot water bath
• Optional: thermometers to monitor the temperature in the hot water bath
• disposable latex gloves

For microscope test:

• dissecting scope, although a light microscope at low power will also work
• slides or Petri dishes

Optional for introduction:

• computer with digital projector to show students slide shows or videos of the Mars Exploration Rover Mission (see Sources section for details)

Setting

Classroom 

Life on Mars - Background

Teacher Background
Mars, Blueberries, and Hematite
Mars Rover - Spirit: This special effects image of the Mars Exploration Rover Spirit was created using a rover model and an image taken by the Spirit navigation camera. Image courtesy of NASA/JPL-Caltech.The Mars Exploration Rover mission provides the inspiration for exciting science experiences. These two rovers represent incredible feats of engineering and have contributed vast piles of data for geology and astrobiology research.

This lesson is built around the discovery of Martian “blueberries” by the rover Opportunity in Meridiani Planum. The blueberries aren’t really blue – they’re actually grey – nor are they the size of blueberries – they are only around 3 millimeters in diameter. When they were first observed scattered across the floor of Meridiani Planum, their composition was an enticing mystery.

Closeup of "blueberries": This image, taken by the rover's microscopic imager, clearly shows the sphere-like grains or "blueberries" that fill Berry Bowl. Image courtesy of NASA/JPL-Caltech.What are they? Their uniformity and symmetrical shape calls to mind the bacterial and fungal colonies grown on agar plates. Could they once have been living things, now frozen or fossilized on the surface of Mars? What about the 3 fused berries in the picture? Does this capture the process by which berries reproduce? That is the question posed to students in this activity, however, this is not a theory supported by scientists. Scientists guessed that the blueberries were concretions, formed when water rich in minerals permeates into porous rock then evaporates, leaving behind the hardened minerals in the spaces. Although originally buried within the rock, as the surrounding rock weathered away, the concretions were freed and left to roll around on the Martian surface.

Berry Bowl with "blueberries": This image from the Mars Exploration Rover Opportunity's camera shows the rock called "Berry Bowl" in the "Eagle Crater" outcrop. Image courtesy of NASA/JPL-Caltech.For several long weeks, the blueberries were too small and scattered to be analyzed accurately with Opportunity’s scientific instruments. Thus the scientists’ theory could not be confirmed. Finally the rover reached a spot nicknamed the “Berry Bowl”. There, enough blueberries had collected in one place for the rover to use its Mössbauer, thermal emission, and alpha particle X-ray spectrometers to decipher its chemical make-up. By comparing the berry cluster in the Berry Bowl with a berry-free patch nearby, scientists were able to determine that the blueberries are composed of hematite (or haematite).

Hematite is the mineral form of iron oxide (rust). It is very common on Earth and is generally found in places where there has been standing water or mineral hot springs. However, it may also be formed volcanically. So, does the hematite blueberries on Mars indicate the former presence of water or were the blueberries formed volcanically? The presence of fused blueberries, like the triplet berry near the center of the image strongly argues that these blueberries were formed through the action of liquid water. Volcanically formed beads are unlikely to fuse along a line in this fashion.

More information on the Mars Exploration Rover mission is available on the NASA/JPL website and specific links of interest to this lesson are provided in the Sources section.

Tips for Teachers
Be aware of several tips as you embark on this open-ended experiment.

The yeast will remain active when added to the nutrient milkshake for a few hours until they run out of nutrients to sustain their growth. Adding more milkshake will reinvigorate the culture.

For students to grow yeast on agar plates, the nutrient agar must include sugars for the yeast to digest. This differs from the agar plates described in the Life Trap activity in which no sugar was required. In addition, it is best to dissolve the yeast-soil sample in water first (approximately 1 part yeast-soil to 2 parts water) and seed the plates with a Q tip dipped in the solution. Dry yeast get too little moisture from the plates alone to grow effectively.

To test for organic molecules, it is important to dissolve the yeast-soil sample in water first (approximately 1 part yeast-soil to 2 parts water). Only the protein test will yield a positive result. If you want to increase the rate of positive results, add 2 tablespoons of flour to the yeast-soil mixture. This will make the starch test give a positive result as well without interfering with any of the other tests the students might conduct.

Student Prerequisites
Students need a thorough understanding of the characteristics of life and must be equipped with several means of testing for life such as growing microbes on agar plates or nutrient-rich solutions, testing for organic molecules, observing cells under the microscope, etc. See the Life Trap, Testing for Life, and Seeing Cells activities.

Life on Mars - Getting Ready

Getting Ready 

For soil samples:

• Sample #1 - Distribute 1 cup clean sand into 10 ziplock bags, around 1.5 tablespoons per bag. Label these “Sample #1”.
• Sample #2 – Mix 1 cup clean playground sand with 4 thoroughly crushed Alkaseltzer® tablets. Distribute the mixture into 10 ziplock bags, around 1.5 tablespoons per bag. Label these “Sample #2”.
• Sample #3 – Mix 1 cup clean playground sand with 8 packages yeast. Distribute the mixture into 10 ziplock bags, around 1.5 tablespoons per bag. Label these “Sample #3”.

For nutrient milkshake: combine 500 ml distilled water, 85 g table sugar, and 85 g all purpose white flour in a 1 liter bottle or flask.

For agar plates: see Life Trap activity for directions on how to mix nutrient agar and pour plates.

For organic molecules tests: see Testing for Life activity for directions on how to set up test stations.

Life on Mars - Lesson Plan

Lesson Plan

1. Open the lesson with a description of the Mars Expedition Rover mission. Show students pictures and, if possible, videos of the rovers and the blueberries that were discovered.
2. Pass out the handout and describe the challenge. NASA has given the class samples of “Martian soils” including “crushed blueberries”. It is the job of each team of students to design 3 tests to determine whether any of the soil samples contain something alive or something that once was alive. They must carefully select the “best” group of 3 tests and write down detailed procedures for how they plan to conduct each test.
3. Describe the materials (especially the nutrient milkshake since this is new to the students) and the different tests available for the students to try. You may want to point out that most of the tests students conducted previously were done with liquids, not solid soil samples. Therefore, for SOME tests, students may wish to mix their sample with water (1 part sample to 2 parts water)
4. Answer any questions then distribute soil samples and hand lenses.
5. Get the students started making initial observations and discussing their experimental design in groups. The experiment should roll along from here. Once students have 3 tests designed and written down, they should come to you for approval before conducting the tests. Soon, students will be conducting various experiments and making discoveries. Expect teams to finish at different rates. Some tests, like the agar plate test, may require 24 hours to see results. Expect to spend at least 2 class periods or more on this activity. Encourage teams that finish early to work on the conclusion questions.
6. When all the data has been collected, discuss the results and their conclusions as a class. Compare the results of the different tests and see whether a unified picture emerges. Discuss conflicting results and the reasons they might have appeared.
7. Inform students that the soil samples weren’t actually from Mars. Allow them to discuss what they think was in each sample but don’t reveal the actual ingredients. Many of my students took some of the samples home to further experiment with them and figure out what was in each one.
8. Tell the students what the actual Mars blueberries were found to be – hematite – and why that discovery is important for understanding the history of Mars and the possibility of discovering life on other planets. 

Life on Mars - Going Further

Going Further

1. See the Imax movie “Roving Mars”. The animation is absolutely incredible. Sadly, little of the scientific discoveries on Mars itself are discussed in the movie but the engineering that went into designing the rovers and getting them to Mars is clearly and dramatically shown.
2. After completing this activity, bake the soil samples at 200 degrees for 30 minutes, or microwave them on high for 5 minutes, to kill the yeast. Then do the activity again. The nutrient milkshake and agar plate tests should now show negative results but the protein test should still detect the presence of the yeast.
3. Study other aspects of Mars such as its size, gravitation, planetary history, etc. NASA provides an extensive list of Mars-related lesson plans.
4. Investigate what the “blueberries” really are – beads of hematite. Bring in samples of hematite and test some of its physical properties using methods described in the History of Rock activity. Hematite stats:
   • Hardness - 6.5, comparable to pyrite
   • Color – reddish grey, reddish brown, grey, dark grey
   • Density - 5.3
   • Luster – metallic
   • Streak – reddish brown
   • A neodymium magnet will show a weak attraction for hematite, regular magnets will not.

Life on Mars - Sources

Sources
This lesson was inspired by a workshop by Steve Ribisi of the University of Massachusetts and Mission 10 from the Life in the Universe curriculum, published by the SETI Institute.

To learn more about the Mars Rovers, go to the NASA/JPL website. The following are some of the highlights from this site that may be used in conjunction with this lesson:

• NASA/JPL produced incredible computer animation sequences documenting the challenge of sending the rovers safely to Mars. I showed my students these videos as a prelude to assigning them an egg drop challenge - each student is given a chicken egg and must design a way to safely cushion the eggs fall from a third story window.
• Read the latest update about the rovers to find out what they are up to.
• To inspire girls in your class to pursue careers in engineering, show them this webcast of women engineers on the Mars NASA team.
• Explore the Mars Fun Zone, a site packed with games and activities designed for kids to learn more about Mars.

To learn more about blueberries and hematite, see:

• The NASA/JPL press release about the blueberries.
• An article about the Mars blueberries by Astrobiology Magazine describes in detail the observations Opportunity made and how these results can be interpreted.
• A press release from the University of Utah comparing the Mars blueberries to hematite concretions found at Grand Staircase-Escalante National Monument in southern Utah. For the Nature article describing the study, go to the Nature website.

Standards
Grade 6
5. Organisms in ecosystems exchange energy and nutrients among themselves and with the environment. As a basis for understanding this concept:
e. Students know the number and types of organisms an ecosystem can support depends on the resources available and on abiotic factors, such as quantities of light and water, a range of temperatures, and soil composition.

Grade 7
Cell Biology
1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope.

Structure and Function in Living Systems
5. The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
a. Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.

Grade 8
Chemistry of Living Systems (Life Sciences)
6. Principles of chemistry underlie the functioning of biological systems. As a basis for understanding this concept:
a. Students know that carbon, because of its ability to combine in many ways with itself and other elements, has a central role in the chemistry of living organisms.
b. Students know that living organisms are made of molecules consisting largely of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.       
c. Students know that living organisms have many different kinds of molecules, including small ones, such as water and salt, and very large ones, such as carbohydrates, fats, proteins, and DNA.

Grades 9-12 Biology
Cell Biology
1. The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept:
a. Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.
b. Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings.
h. Students know most macromolecules (polysaccharides, nucleic acids, proteins, lipids) in cells and organisms are synthesized from a small collection of simple precursors.

Grades 9-12 Chemistry
Organic Chemistry and Biochemistry
10. The bonding characteristics of carbon allow the formation of many different organic molecules of varied sizes, shapes, and chemical properties and provide the biochemical basis of life. As a basis for understanding this concept:
a. Students know large molecules (polymers), such as proteins, nucleic acids, and starch, are formed by repetitive combinations of simple subunits.
b. Students know the bonding characteristics of carbon that result in the formation of a large variety of structures ranging from simple hydrocarbons to complex polymers and biological molecules.
c. Students know amino acids are the building blocks of proteins.

All Grades
Investigation and Experimentation
7. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
a. Select and use appropriate tools and technology (including calculators, computers, balances, spring scales, microscopes, and binoculars) to perform tests, collect data, and display data.
e. Communicate the steps and results from an investigation in written reports and oral presentations.