September 12, 2013
Scientists May Soon Have New Tools To Answer The ‘Are We Alone’ Question
Lee Rannals for redOrbit.com - Your Universe Online
Scientists are working on new tools to help detect whether or not life exists on planets far away from our Solar System.
Life on Earth is able to send off signals into the atmosphere, such as microbes emitting methane and nitrous oxide. When these chemicals are present in sufficient quantities they become indicators of life and are known as atmospheric biomarkers. Detecting them in the atmosphere of exoplanets could indicate whether or not life exists on another planet.
Biomarkers have never been spotted on an exoplanet because their signal is so faint, but a new generation of telescopes like the European Extremely Large Telescope may be able to detect the chemical signatures. Lee Grenfell presented research at the European Planetary Science Congress about how scientists can detect these biomarkers in the future.
“The main aim of our work is to assess the possible range of biomarker signals that might be detected by future telescopes,” Grenfell, who submitted his research in the journal Planetary & Space Science, said in a statement. “To do this, we developed computer models of exoplanets which simulate the abundances of different biomarkers and the way they affect the light shining through a planet’s atmosphere.”
Astronomers have been able to use techniques to discover information about the conditions present in exoplanets by observing as a planet passes in front of a star. Biomarkers would be detected in a similar way, but the signal would be so weak that scientists need a solid understanding based on theoretical models before they can decipher the data.
“In our simulations, we modeled an exoplanet similar to the Earth, which we then placed in different orbits around stars, calculating how the biomarker signals respond to differing conditions,” Grenfell explains. “We focused on red-dwarf stars, which are smaller and fainter than our Sun, since we expect any biomarker signals from planets orbiting such stars to be easier to detect.”
The team confirmed that there appears to be a "Goldilocks" effect when it comes to the amount of ultraviolet radiation from the star to which the planet is exposed. With weak UV radiation, less ozone is produced in the atmosphere and its detection is challenging. Too much UV can cause increased heating in the middle atmosphere that weakens the vertical gradient and destroys the signal.
“We find that variations in the UV emissions of red-dwarf stars have a potentially large impact on atmospheric biosignatures in simulations of Earth-like exoplanets. Our work emphasizes the need for future missions to characterize the UV emissions of this type of star,” said Grenfell. “For the first time we are reaching a point where serious scientific debate can be applied to address the age-old question: are we alone?”