A shadow biosphere is a postulated microbial biosphere of Earth that uses radically different biochemical and molecular processes than currently known life. While life on Earth is relatively well-studied, the shadow biosphere may still remain unnoticed because our exploration targets our biochemistry primarily.
Benner, Ricardo and Carrigan argue that, if organisms based on RNA have once existed, they may still be alive today, unnoticed because they don't contain ribosomes, which are usually used to detect living organisms. They suggest searching for them in environments that are low in sulphur, that are spatially constrained (for example, minerals with pores smaller than one micrometre), or that cycle between extreme hot and cold.
Other proposed denizens of the shadow biosphere include organisms with chirality opposite of ours, that use some of the non-standard amino acids, or that use arsenic instead of phosphorus.
No comments:
Post a Comment