This has traditionally been done through radio and optical telescopes and extracting signals from the “noise” of the universe.
By using new and more powerful computers, we may discover intelligent alien life in 20 years. Recently though, scientists have started thinking about different ways to track extra-terrestrial organisms.
We may have been searching for the wrong signals. For instance, water has always been considered the number-one indicator of the presence of life. No longer: methane is on the hot list.
Since the detection of this element in its atmosphere, Mars has been scanned to identify the source of a methane production-depletion cycle.
The hypothesis that methane is delivered by meteorites was ruled out. Was it then the action of methane-producing microorganisms? The ExoMars Trace Gas Orbiter, NASA and ESA’s First Joint Mission To Mars, is scheduled for 2016. One of its main objectives is to investigate this puzzle.
“We just don’t know what the tell-tale signs for life would be in such an atmosphere because it is so vastly different from ours. That said, it will change in a flash if Chris McKay finds life on Titan and can tell us what it produces and what we could look for remotely with a telescope.” Lisa Kaltenegger, astrophysicist
Well, it’s a liquid, and it’s well-known that one of the qualities that makes water ideal for life is that it allows essential molecules to bond together and support life.
But another good reason is that we know 90 percent of the methane in our atmosphere is created by living organisms. And it has been hypothesized that a methane-based, alien life form would consume hydrogen and exhale methane instead of carbon-dioxide, therefore resulting in a depletion of hydrogen on the surface of the planet. Guess what? We have signs that this happens!
“As Sherlock Holmes said, eliminate all other factors and the one that remains must be the truth. The list of possible sources of methane gas is getting smaller and excitingly, extraterrestrial life still remains an option. Ultimately the final test may have to be on Mars.” Mark Sephton, Department of Earth Science and Engineering at Imperial College London
Saturn's Moon Titan
It’s Titan, Saturn’s biggest moon and by far the most interesting object in the solar system.
In June, NASA’s Cassini satellite confirmed the presence of bodies of liquid methane. It also spotted a mysterious “island” in the middle of its second-largest lake!
Whatever the truth is about the presence of bacterial, methane-based life on Mars and Titan, scientists are actively searching for a methane-habitable zone around stars. It is based on the well-known model of the HD zone but better suited to detect methane-based organisms.
A joint effort of researchers from University College London and the University of New South Wales in Sydney, the project has now developed a powerful and innovative tool to hunt for methane in space object signatures.
By calculating how methane is absorbed by a wide range of different molecules, it will allow scientists to find traces of it at higher and lower temperatures than previously possible. These relatively hotter and colder worlds will be equally hosted by Sun-like stars and red dwarves, opening up the field of extraterrestrial life to new, exciting possibilities.