Seager’s new equation makes no assumption that extraterrestrials are intelligent and using radio technology. Instead, she simply works on the idea that life of any type may be present in sufficient abundance to alter the chemical composition of its planet’s atmosphere.
On Earth, for example, our atmosphere has been driven to a specific chemical composition by the combined metabolisms of all the living things. It is as distinctive as a fingerprint. So, by analysing the atmosphere of another planet, we may be able to detect the presence of life, even if it is only pondweed.
Nevertheless, Seager’s new equation suffers many of the same drawbacks as Drake’s original: we have no idea what value to assign to most of the factors.
Last year, I appeared at the International Festival of Authors in Toronto alongside Canadian poet Larissa Andrusyshyn. Realising the probabilistic nature of the life, the bottom line is that the factors are too loosely constrained for either to have any quantitative value.
The only way to know if there is truly life on other worlds is to design and build missions that will look for it. Thankfully, Seager is at the forefront of that effort too. Her planet-finding TESS, will be launched by Nasa around 2017 and could locate hundreds of Earth-sized planets.
Stuart Clark - Guardian