(May 14, 2011 at 4:03 am)Welsh cake Wrote: What technological methods do we currently have that can detect life on other planets?
Presently we're still trying to develop more sophisticated detection methods for terrestrial Earth-like exoplanets orbiting in the habitable zone surrounding its star. Even if we discover another world with the exact likeness, characteristics and chemical composition of our own planet (Earth's twin if you will) that still doesn't get us the proof we need to confirm living organisms on its surface via direct observation since extrasolar planets are obviously extremely faint light sources compared to their parent stars.
One could remotely detect strong leading evidence, if not conclusive proof, of life on another planet by looking for spectroscopic evidence of high concentration of gases that are chemically unstable in the environment of the planet, but which would be natural end product of any biological respiration process.
One example would be methane in a warm planetary environment subjected to substantial UV radiation from its parent sun. Another would be free oxygen. Both compounds either breakdown or chemically react within geologically short periods. High concentration of these gases in a warm atmosphere would indicate sustained surface process systematically manufactureing those gases.
