via Astronomy Now.
The public are well aware of the Drake Equation. This equation from the 1960s takes a series of educated guesses as well as better known values and tries to calculate the number of detectable civilisations from them. However, the result is a rule of thumb and uses a lot of conjecture in an attempt to look for radio signals that may very well be just too weak to ever detect over the vast reaches of space.
Now researchers Dr Axel Hagermann and Professor Charles Cockell from the Open University are creating a habitability index. This is a series of parameters known to have positive or negative effects on life – is the planet too close/far from the star, does the atmosphere block x-rays but let in light usable for photosynthesis, is the orbit within acceptable levels of eccentricity for plate tectonics, is the star’s position in the galaxy suitably quiescent? These parameters can then be used in any given system to search for the most likely habitable worlds, be they planets or satellites.