From Eric Kvaalen, Les Essarts-le-Roi, France
When astronomers say that, sooner or later, we will come across an exoplanet with a nitrogen/oxygen-rich atmosphere, or that, by 2060, we are likely to have discovered planets where it is hard to explain the data without there being life, they are assuming, with no good reason, that life can easily arise if the conditions are right(20 September, p 23).
The chance that all the hugely complex machinery of even the simplest cells will arise on a planet, even with the right conditions, is, in my view, very small.
