Lesson 6: Search for Life in Our Solar System
Key Learning Objectives:
Appreciate the past, current and future strategies of searching for life in our solar system
Appreciate that scientific experiment do not always give conclusive results, and that long-term studies over many generations of instruments is often required to explore a research topic
Discuss scientific reasoning that allows scientists to understand if life might exist on another planets in our solar system
In this lesson you'll find...
A Close Study of Mars
Life on Other Planets within Our Solar System
A Close Study of Mars
In 1976, NASA’s Viking Landers detected methane in an incubated soil sample on Mars which was a major discovery for scientists. Since atmospheric methane on Earth is derived from biotic sources, it is natural to assume that methane is a significant biosignature gas to indicate some form of life on Mars. Many hypotheses have been put forward to account for the methane production on Mars, with biotic life a possible scenario. Research groups have studied deserts on Earth in order to better understand if life in these arid environments could release methane gas. Anaerobic decomposition of organic material is a source of methane gas and was observed in soil samples in deserts in Utah which supports the hypothesis of biological life on Mars in the soil. Coupled with the discovery of ice on Mars, some form of life is plausible.
However, Methane is also produced by geological sources, such as volcanoes, which is a non-biological source. Volcanic methane is usually accompanied by a release of sulfur dioxide which is not present in the Martian atmosphere, suggesting that this is not a possible scenario for methane production on Mars. Methane is an unstable gas and if levels are constant in the atmosphere of a planet, this suggests that there is a life form that consistently produces it. These methane peaks were found to occur every 24.66 hours (which is one Martian “day”) which can indicate that there is some form of life that exists in a circadian rhythm.
NASA’s Curiosity Rover has since been sent to Mars and did not detect methane in early 2013 which discounted the results of the Viking mission. However, in late 2013 and early 2014, it did detect a peak in methane levels in the surrounding air which suggested that any possible life on Mars may undergo a yearly cycle as Earth does. These results have been repeatedly analysed and new missions are planned for Mars to redetect methane peaks in the atmosphere.
Currently, it is unknown whether biotic or abiotic processes produce the methane found in the Martian atmosphere but many studies conclude that from this evidence, life on Mars is “likely present and active”.
Activity
The image on the left illustrates the possible sources and sinks of methane on Mars, i.e., the scenarios we think methane is form and destroyed on Mars.
Take some time to analyse the image and discuss whether or not methane on Mars can indicate the presence of life.
Life on Other Planets within our Solar System
Scientists have proposed life may be present in many solar system bodies beyond Mars. Popular targets for solar-system life beyond Earth and Mars include the moons: Europa, Enceladus, and Titan. Less popular environments include: Venus, Triton, Ceres, and Pluto.
Activity: Research then Share
For an assigned planetary body, research the following questions individually or in pairs as directed by your teacher.
Where is the body?
What is the body like (atmosphere, temperature, source of energy, potential solvent for life)?
Why might life exist there?
How would scientists look for life on that body? Are there any proposed missions to look for this life?
You can find some inspiration by reading the following article:
Eight other worlds in our solar system might have life beyond Earth
