- 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.
- 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.
- 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)
- Answer any questions then distribute soil samples and hand lenses.
- 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.
- 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.
- 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.
- 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.
Submitted by irene on Wed, 2006-07-26 19:01.
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”.
Submitted by irene on Wed, 2006-07-26 19:00.
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.
Submitted by irene on Wed, 2006-07-26 18:49.
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
Groups of 2-3 students
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
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)
Submitted by irene on Wed, 2006-07-26 18:44.
Mars Exploration Rovers: This special-effects image combines a model of the Mars rover Opportunity and 46 photogrpahs that Opportunity took of "Burns cliffs" near the edge of "Endurance Crater". Image courtesy of NASA/JPL-Caltech/Cornell.
In the summer of 2003, NASA’s Jet Propulsion Laboratory launched two Mars Exploration Rovers - Spirit and Opportunity - towards Mars. They landed on January 3rd and 4th, 2004. Their primary scientific goal was to study the geology of Mars and search for signs of water. Although they were expected to last only 3 months, they have been vigorously sending back data for over 2 years and are still going strong! In this activity, students receive simulated Martian soils and are given the task of designing 3 tests to determine whether the soil sample contains something alive or something that was once alive. They may use any of the tools from the previous lessons – agar plates, tests for organic molecules, microscopes, or something of their own design. This assignment allows students an opportunity to demonstrate what they have learned throughout the unit, both about scientific experimentation and about the special characteristics of living things.
Can describe the necessary characteristics of life.
Can categorize objects as alive or not alive using self-generated data.
Can demonstrate that all living things will grow and reproduce when provided with the proper nutrients and environmental conditions.
Can demonstrate that living things are made of organic molecules.
Can test for the presence of protein, glucose and starch.
Can design an experiment.
Can make observations and keep track of data over several days.
Can interpret the results of an experiment.
Submitted by irene on Wed, 2006-07-26 18:40.
All the materials needed for this lab may be purchased from Flinn Scientific or other science supply companies.
- Protein test - Biuret solution (Flinn Scientific catalog #B0050, $4 for 100 ml) an alternative test for protein uses Ninhydrin solution (Flinn Scientific catalog #N0039, $9.50 for 100 ml)
- Glucose test - Benedict’s solution (Flinn Scientific catalog #B0171, $3.50 for 100 ml qualitative solution and #B0172, $5 for 100 ml quantitative solution) an alternative test for glucose that does not require the hot water bath is to use glucose test strips that can be purchased from the pharmacy for diabetic urine testing (approximately $15-20 for a bottle of 100 strips, double your supply by cutting each strip lengthwise)
- Starch test – iodine tincture (purchase from your local pharmacy or Flinn Scientific catalog #I0009, $5 for 100 ml)
- Positive control for glucose test – either use glucose solution (Flinn Scientific catalog #G0024, $7.75 for 100 ml) or dissolve glucose tablets for diabetics in water (purchase from your local pharmacy)
Submitted by irene on Tue, 2006-07-25 15:54.
- Collect student notebooks with data tables and conclusion questions.
- Revisit the characteristics of life list from the Is It Alive? activity. Revise the criteria as necessary.
- Have students propose a method for testing for life on another planet. For instance, how could you equip a Mars rover with the tools necessary for testing for organic molecules. What tests would you include and why?
Submitted by irene on Tue, 2006-07-25 15:47.
- Begin class with a discussion of food and the food groups. Each of the major organic molecules can be correlated to different classes of foods (protein = meat and beans group, simple sugars (glucose and fructose) = sweets and fruit groups, complex carbohydrates (starch) = grains group, lipids = fats group). Allow this discussion to lead into the idea that all food items are made up of building block organic molecules. Food items were all once alive. Therefore, all living things are made up of these same building blocks that our food is made of.
- Go into as much detail as necessary for your students on the biochemistry of organic molecules. You may want to describe the relationship between glucose and starch at this time.
- Pass out the student lab handouts. Describe the activity to your students. Each student will test solutions at 3 different stations. They should choose one solution from each of the following categories: “never alive”, “once was alive” and a mystery solution. They will be testing for protein, starch and glucose. In addition to the 3 solutions you will carry around with you, there will also be a 4th solution at each test station. This is one that is guaranteed to cause a color change so that you know what a color change looks like.
- Show students any special procedures, such as how to prepare the hot water bath. Answer any questions.
- Allow students 5 minutes to gather their materials and then 10-15 minutes at each test station. Help groups that are having difficulty.
- When all testing is complete and teams have cleaned up, create a master table on the board like the one below to collect all the teams results for all the different tests.
Submitted by irene on Tue, 2006-07-25 15:45.
- Order materials.
- Set up testing stations. It is recommended that the activity be arranged so that no more than 6 students (2 groups) share any given station. Thus, you may need to set up 2 of each type of testing station and position them strategically about the room.
- The protein station needs – gloves, Biuret solution, 2-4 eye droppers, milk, protein test station directions
- The starch station needs – iodine tincture, 2-4 eyedroppers, cornstarch solution, starch test station directions
- The glucose station needs – gloves, Benedict’s solution, 2-4 eyedroppers, glucose solution, glucose test station directions, hot water bath, access to boiling water
- Set up test tube racks with 4 test tubes per rack
- Set out test solutions and beakers
- Set out eyedroppers
- Set out labeling tape and permanent markers
Submitted by irene on Tue, 2006-07-25 15:40.
All living things (at least on Earth) are composed of organic molecules. All organic molecules include carbon-hydrogen bonds. The major classes of organic molecules are:
- Carbohydrates (including glucose and starch)
- Nucleic acids
GlucoseCarbohydrates are particularly important for energy storage in living things. Sugars and starches are common examples of carbohydrates. Carbohydrates are can be found as simple sugars or monosaccharides such as glucose, a ring of 6 carbons with attached hydrogens and oxygens (C6H12O6). Other simple sugars include fructose (a common sugar found in fruit) and galactose. These simple sugars may be joined together in pairs. For instance, sucrose (table sugar) is a combination of glucose and fructose. Similarly lactose (the sugar found in milk) is a combination of glucose and galactose. Finally, simple sugars may be assembled into long chains called polysaccharides. Starch is a familiar example of a polysaccharide that is found in many foods including potatoes, flour, and corn. It is made from a long chain of glucose molecules.
Submitted by irene on Tue, 2006-07-25 15:38.