Astrobiology in Europe, 20 years of expectations

During 20 years, the European astrobiologists collaborated within EANA, the European Astrobiology Network Association, to help European researchers developing astrobiology programmes to share their knowledge, to foster their cooperation, to attract young scientists to this quickly evolving interactive field of research, and to explain astrobiology to the public at large. The experiment of Stanley Miller in 1953 launched the ambitious hope that chemists would be able to shed light on the origins of life by recreating a simple life form in a test tube. However, the dream has not yet been accomplished, despite the great volume of effort and innovation put forward by the scientific community.

Prebiotic Chemical Refugia: Multifaceted Scenario for the Formation of Biomolecules in Primitive Earth

The origin of life was a cosmic event happened on primitive Earth. A critical problem to better understand the origins of life in Earth is to glimpse in which chemical scenarios the basic building blocks of biological molecules could be produced. Classic works in pre-biotic chemistry frequently considered early Earth as a homogeneous atmosphere constituted by chemical elements such as methane (CH4), ammonia (NH3), water (H2O), hydrogen (H2) and hydrogen sulfide (H2S). Under that scenario, Stanley Miller was capable to produce amino acids and solved the question about the origin of proteins. Conversely, the origin of nucleic acids has tricked scientists for decades as nucleotides are complex though necessary molecules to allow the existence of life. Here we review possible chemical scenarios that allowed not only the formation of nucleotides but also other significant biomolecules. We aim to provide a theoretical solution for the origin of biomolecules at specific sites named “Prebiotic Chemical Refugia”. A prebiotic chemical refugium should therefore be understood as a geographic site in prebiotic Earth on which certain chemical elements were accumulated in higher proportion than expected, facilitating the production of basic biomolecules. Plus, this higher proportion should not be understood as static, but dynamic; once the physicochemical conditions of our planet changed periodically. This different concentration of elements, together with geochemical and astronomical changes along days, synodic months and years provided somewhat periodic changes in temperature, pressure, electromagnetic fields, and conditions of humidity; among other features. Recent and classic works suggesting most likely prebiotic refugia on which the main building blocks of biological molecules might be accumulated are reviewed and discussed.

Extraterrestrial Microfossils in Meteorites and the Panspermia Hypothesis

I review the experiments by Stanley Miller and Sidney Fox on the production of amino acids and unicellular forms under primitive terrestrial atmosphere conditions. I continue with a review of the evidence for and against unicellular organisms in the Orgueil meteorite and the ALH84001 martian meteorite. I conclude that the evidence argues against the panspermia hypothesis of Fred Hoyle and Nalin Chandra Wickramasinghe.

Do aliens dream of offworld sheep?

The Stanley Miller experiment suggests that amino acid-based life is ubiquitous in our universe, although its varieties will not have followed the particular, highly contingent and path-dependent, evolutionary trajectory found on Earth. Are many alien organisms likely to be individually conscious in ways we would recognize? Almost certainly. Will alien consciousness require a ‘sleep cycle’? A strong argument suggests it will. Can some species develop analogs to culture and high-order technology? Less likely, but still fairly probable. If so, will we be able to communicate with them? Only on a basic level, and only with profound difficulty. The reasoning is fairly direct and involves convolution of a learned heritage system with individual and collective consciousness.