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Methane research boosts the hunt for alien life

Jenny Winder, News Writer
Jun 17, 2014, 14:00 UTC

Sen—A powerful new model that focuses on methane to detect life on planets outside of our Solar System more accurately than ever before, has been developed by University College London (UCL) scientists.

Methane, the simplest organic molecule, is widely acknowledged to be a sign of potential life.

Now researchers have developed a new spectrum for "hot" methane which can be used to detect the molecule at temperatures above that of Earth, up to 1,500K/1,220°C, something which was not possible before.

Astronomers analyse the way in which the atmospheres of remote planets absorb starlight of different colours and compare it to a model, or "spectrum", to identify different molecules and find out what the exoplanets are made of.

Professor Jonathan Tennyson (UCL Department of Physics and Astronomy), co-author of the study, said: "Current models of methane are incomplete, leading to a severe underestimation of methane levels on planets. We anticipate our new model will have a big impact on the future study of planets and 'cool' stars external to our solar system, potentially helping scientists identify signs of extraterrestrial life."

In the new study the researchers used some of the UK's most advanced supercomputers, provided by the Distributed Research utilizing Advanced Computing (DiRAC) project and run by the University of Cambridge, to calculate nearly 10 billion spectroscopic lines, each with a distinct colour at which methane can absorb light.

The new list of lines is 2,000 times bigger than any previous study, which means it can give more accurate information across a broader range of temperatures than was previously possible.

The new model was tested and verified by successfully reproducing in detail the way in which the methane in failed stars, called brown dwarfs, absorbs light.

Meanwhile, in lab experiments, NASA scientists have matched the spectral signature of an unknown material the Cassini spacecraft detected in Titan's atmosphere at far-infrared wavelengths.

The spectral signature of the material suggested it was made up of a mixture of molecules. To investigate that mixture, the researchers combined gases in a chamber and let them react.

With the right gases, under the right conditions, the reactions in the lab should yield the same products found in Titan's smoggy atmosphere, but the possibilities are almost limitless in this case.

NASA scientists matched the spectral signature of an unknown material detected in Titan's atmosphere. The material contains aromatic hydrocarbons that include nitrogen, a subgroup called polycyclic aromatic nitrogen heterocycles. Image credit: NASA/Goddard/JPL

The logical starting point was to begin with the two gases most plentiful in Titan's atmosphere: nitrogen and methane. But these experiments never produced a mixture with a spectral signature to match to the one seen by Cassini. The best results were obtained when the researchers added a third gas, an aromatic that contained nitrogen.

"This is the closest anyone has come, to our knowledge, to recreating with lab experiments this particular feature seen in the Cassini data," said Joshua Sebree, the lead author of the study.

Now that the basic recipe has been demonstrated, future work will concentrate on tweaking the experimental conditions to perfect it.