Comments on the cosmic convergence of nonexpansive maps

This note discusses some aspects of the asymptotic behaviour of nonexpansive maps. Using metric functionals, we make a connection to the invariant subspace problem and prove a new result for nonexpansive maps of $$\ell ^{1}$$ ℓ 1 . We also point out some inaccurate assertions appearing in the literature on this topic.

Testing the universality of biology: a review

We discuss whether it is possible to test the universality of biology, a quest that is of paramount relevance for one of its most recent branches, namely astrobiology. We review this topic in terms of the relative roles played on the Earth biota by contingency and evolutionary convergence. Following the seminal contribution of Darwin, it is reasonable to assume that all forms of life known to us so far are not only terrestrial, but are descendants of a common ancestor that evolved on this planet at the end of a process of chemical evolution. We also raise the related question of whether the molecular events that were precursors to the origin of life on Earth are bound to occur elsewhere in the Universe, wherever the environmental conditions are similar to the terrestrial ones. We refer to ‘cosmic convergence’ as the possible occurrence elsewhere in the Universe of Earth-like environmental conditions. We argue that cosmic convergence is already suggested by observational data. The set of hypotheses for addressing the question of the universality of biology can be tested by future experiments that are feasible with current technology. We focus on landing on Europa and the broader implications of selecting the specific example of the right landing location. We have previously discussed the corresponding miniaturized equipment that is already in existence. The significance of these crucial points needs to be put into a wider scientific perspective, which is one of the main objectives of this review.