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Distinguishing Between Trace Fossils as Organism-Substratum Interactions and Traces of Chemical Fingerprints from Life

Introduction: The phrase " traces of life " has been at the center of research activity in the search of new evidence for the earliest or most extreme life on Earth, and for extraterrestrial life on Mars and such other planetary bodies as Europa and Titan. This phrase has been used loosely and with many different meanings and implications. A problem exists, however, because unnecessary confusion is created. The purpose here is to review and clarify the different types of " traces of life " and to delve into the ways of distinguishing one from the other and their significance. The term " trace " has traditionally been used to define the results of and animal interacting with a substratum. This is also known as the study of ichnology. Ichnology, more broadly defined, is the study of organism behavior and its products—trace fossils. A trace fossil is the product of an organism interacting with a substratum in an environment that generates a three-dimensional physical structure. combination of these as multifunctional structures, which an organism(s) does while it is alive. Objects that are not trace fossils include molds, casts, and impressions of body fossils. Eggs and egg shells, internally precipitated structures, and organic residues and biomarkers are not trace fossils. The organisms involved in producing behavior include all trace-making representatives of the Bacteria, Archaea, and Eucarya. All organisms, even the smallest and simplest, show one or more kinds of biophys-icochemical behavior that can become a trace fossil if the structure passes through the taphonomic barrier. Trace fossils, nevertheless, have a greater preservation potential than body fossils because they are excavated, constructed, and already part of a substratum. Also, one organism can make tens to millions of trace fossils in a lifetime, which have a better chance by numbers of making it into the fossil record compared to the remains of the organism. A substratum includes a host of materials. Grains include the surfaces and interiors of mineral and rock fragments, and glass shards of all sizes. Sediments with different consistencies due to different water saturation include soupgrounds, softgrounds, firmgrounds, and hardgrounds. Rocks include sedimentary, igne-ous, and metamorphic substrata. Organisms, both liv