Loess and life out of Earth?

Abstract

© 2015 Elsevier Ltd and INQUA. Loess is a homogeneous, typically nonstratified, porous, friable, slightly coherent, often calcareous, fine-grained, silty, pale yellow, wind blown (aeolian) and often by water reworked sediment that is distributed on continents world-wide. Recent studies have highlighted the importance of biological loess crusts in trapping and transforming aeolian material into loess and also in prevention from wind and water erosion of deposited material.Some planets and satellites in our solar system are characterized by conditions comparable to those related to loess formation in terrestrial environments. Given the requirements for loess deposition on Earth, this study aims to ask the following questions: 1) if loess-like sediment formation is possible outside Earth, what are the mechanisms of sediment deposition and preservation; 2) could the possible loess-like sediments be stabilized through the activity of extraterrestrial equivalents of biological loess crusts found on Earth? As loess formation on Earth is related to biological activity, we propose a new direction in the search for extraterrestrial life: evidence about extraterrestrial loess might indicate extraterrestrial life connected to loess formation.On the basis of comparative analysis of some astrophysical conditions of seven celestial bodies, we propose Mars and Titan, and possibly Venus and Io, to be assessed for evidence of loess deposition and the possible presence of related life forms and their biomarkers. Following recent advances in our understanding of terrestrial loess deposition we propose new indicators of extraterrestrial life research - biomarkers in loess (cyanobacterial and other microbial).