Minerales alienígenasmodelos de formación en la Tierra

Laburpena

Astrobiology is concerned with understanding the possible existence of life outside our planet assuming that, if microor- ganisms are the most common type of life on Earth, they probably will be on different celestial bodies of the Milky Way. Microbes can make minerals and rocks, biominerals and stromatolites, which have been found along the Earth’s geological record for billions of years. These microbial rocks might be found on celestial bodies with recent or ancient alien life. As it is often easier to locate the works of living beings than themselves, the study of extra-terrestrial rocks could allow identifying biosignatures of alien life in other worlds, since they could be detected in petrological analyses. Harsh environmental con- ditions that prevail in other celestial bodies are similar to those of the Earth’s ecosystems where extremophiles subsist. The hypersaline lakes of Lillo (Toledo) and the alkaline ones of Coca (Segovia) are excellent natural laboratories to study the biosignatures that could be found on different planets and moons. We propose a didactic activity for visualizing biomineral precipitation using dynamic models of balls (particles) that represent solutions. Cations (steel balls) have two small squares of hook velcro attached and anions (pearl marbles) have loop velcro. Water molecules (glass marbles) have nothing stuck or little dots of velcro indicating its dipolar nature. A magnet (3x5 cm) represents a bacterium. Balls are placed on a laboratory tray, which is shaken repeatedly showing that mineral formation (groups of marbles stuck by velcro) is difficult. Then, the magnet is placed on the tray, which is shaken again, showing that steel cations glue to the bacterium cell wall by the residual charges that organic matter presents. Biominerals around the bacteria are thus observed. Evaporation can also be simulated by eliminating water molecules favouring mineral precipitation.