KS2 science: Is there life on mars?

As you read this, NASA’s Curiosity rover is searching for signs of life on the Red Planet. What better opportunity to use contemporary science to spark your own investigations in the classroom, asks Deborah Herridge?

NASA’s planetary rover, Curiosity, landed on the planet Mars on 6th August 2012, tasked with investigating the Martian climate and landscape. Its mission is to determine whether the landing site, inside Gale Crater, has ever had the environmental conditions necessary to support life.

Although Mars has long been a focus for writers of science fiction, we’re not talking ‘little green men’ here, rather little red bacteria! Curiosity will analyse samples scooped from the soil and drilled from rocks, with the ultimate aim of finding out whether there has ever been, or ever could be, life on Mars.

1. The Red Planet “What life exists in extreme conditions on Earth?”

The Martian environment is one of extremes; the average temperature is -55° with a temperature low of -143° at the polar ice caps. The distinctive red colour of the planet’s arid, rocky surface is due to a dusty soil containing lots of iron. So the Red Planet isn’t really red – it’s rusty. On Earth we have extreme environments too and, extraordinarily, life can still be found in these places. The Rio Tinto river in Spain flows blood red through Andalucia. It is red because iron is dissolved in the water. The water itself is highly acidic, almost as acidic as stomach acid.

For comparison, investigate the acidity or alkalinity of common liquids in the classroom by placing drops on Universal Indicator and checking the results against the pH scale. Try lemon juice, liquid soap, cola, milk and tea.

You’d imagine that no life could possibly survive in the extreme conditions of the Rio Tinto, but scientists have discovered the acid is actually a waste product of billions of bacteria living in the water. Astrobiologists now think Mars might have had a similar environment in the past. What other extreme environments on Earth support life? Encourage the children to find out about ‘extremophiles’ – organisms that can survive in extreme conditions such as volcanoes, geysers and hot springs.

2. Looking for life “Come up with a definition for ‘life’”

Can Mars support life? Discuss with the children what makes something alive. Most children recognise something as being alive or not alive; they can probably give reasons for a puppy being a living creature and a table not being alive. Guide this discussion until, as a class, you come up with a definition of ‘life’. You might consider movement, the ability to reproduce, grow, feed, excrete, sensitivity to the environment and some metabolic processes that can be detected by the exchange of gases (respiration). Encourage children to make collections of pictures of living and non-living things. To extend the discussion, think about your definition in relation to things such as fire, clouds or seeds.

3. We need water “Test rocks for evidence of past life”

Scientists have yet to find any evidence for life on the barren planet, but we are still looking and one of the main things we’re searching for is water.

The Curiosity rover tests tiny samples of dust and rock from the surface for evidence of life on Mars. We know that there is no liquid water on the surface of Mars now, but perhaps there was in the past?

One of the key indicators of whether water had existed on the surface at some point in the distant past can be found by looking for evidence in the rock. Rocks like limestone and chalk contain lots of carbonates and were formed, crucially for us, in layers of sediment laid down by the movement of rivers or seas – water!

In the classroom, you can be a NASA planetary geologist and test for water formed rocks. Carefully grind up a selection of rock samples or use small chips of rocks and place each one in a small cup of distilled white vinegar (this acts as the acid). If your rock is water formed and has carbonates in it, it will fizz.

4. It’s alive! “Investigate ‘Martian’ soil samples”

For an exciting exploration of the Martian landscape, role-play a NASA scientist. You have three samples to test from the Martian surface and need to look for signs of life.

The teacher needs to do some preparation without the children’s knowledge. Prepare three samples of dry compost mixed with sand. Each group should have half a cup of each (about 50ml) labelled 1, 2 and 3. In sample 1, mix in a teaspoon (5ml) of sugar. In sample 2, mix in the sugar and add 5ml of dried yeast. In sample 3, mix in 5ml of sugar and one tablet of powdered Alka-seltzer.

Give the children the three ‘Martian’ soil samples. Look carefully at the samples through a hand lens. Can you determine if anything is alive in there? Re-cap on the indicators of life.

Think carefully about respiration, excretion, reproduction and growth. Now add 50ml of warm water to each of the samples in turn and observe what happens.

Record your observations and come back after 10 minutes to repeat the observations and notice any changes.

In sample 1, all that should happen is that the sugar will dissolve. In samples 2 and 3, however, we can see some kind of chemical reaction happening. In 2, the reaction lasts a long time but in 3 it is over quite quickly. From this, could we deduce which of the samples might contain life?

Discuss how we might be able to tell the difference between a chemical change in a non-living process (Alker-seltzer) and a living process (yeast growth).

5. Build your buggy “Construct a remote controlled vehicle powered by electricity”

Controlled from Earth, Curiosity is an extreme example of a remote sensing vehicle. This is the ideal opportunity for older children to use construction kits such as K’nex or LEGO to build a vehicle powered by electricity and driven with remote controlled motors.

Begin by looking at photographs of Curiosity. These can be found on the NASA Mars Science Laboratory website (mars.jpl.nasa.gov/msl/mission /rover). Look carefully at the rover’s construction. Ask children to design and annotate their own version of Curiosity, paying careful attention to the terrain it needs to navigate (images of the Martian landscape can be found at tinyurl.com/tprover). Use the construction kits to translate the children’s designs into working models. Experiment with pulleys and gears and investigate how to change the speed or direction of the vehicle.

Curiosity’s movement is controlled from Earth; sent through radio waves travelling at the speed of light it can still take 12 minutes for a command to reach Curiosity and for the response to get back to the command base.

Recreate this nerve-wracking expedition by setting up a Martian obstacle course in the hall or outside. Have the rovers navigate a clear route through your obstacles, but to make the race more challenging, blindfold the controller of the vehicle and have a teammate give the driver commands to follow.

GET INVOLVED

NASA’s website (nasa.gov) has extensive resources, information, video clips, games and competitions for children to access, not just about the Curiosity rover, but about space exploration in general. The Children’s BBC Newsround website has some great footage, facts and information about the Curiosity mission (bbc.co.uk/newsround/ 19794503)