False negatives Opposite to false positives, false negative biosignatures arise in a scenario where life may be present on another planet, but there are some processes on that planet that make potential biosignatures undetectable. This is an ongoing problem and area of research in the preparation for future telescopes that will be capable of observing exoplanetary atmospheres. Human limitations There are many ways in which humans may limit the viability of a potential biosignature. The resolution of a telescope becomes important when vetting certain false-positive mechanisms, and many current telescopes do not have the capabilities to observe at the resolution needed to investigate some of these. In addition, probes and telescopes are worked on by huge collaborations of scientists with varying interests. As a result, new probes and telescopes carry a variety of instruments that are compromises to everyone's unique inputs. In order for a different type of scientist to be able to detect something not related to biosignatures, a sacrifice may have to be made in the capability of an instrument to search for biosignatures. Examples Geomicrobiology The ancient record on Earth provides an opportunity to see what geochemical signatures are produced by microbial life and how these signatures are preserved over geologic time. Some related disciplines such as geochemistry, geobiology, and geomicrobiology often use biosignatures to determine if living organisms are or were present in a sample. These possible biosignatures include: (a) microfossils and stromatolites; (b) molecular structures (biomarkers) and isotopic compositions of carbon, nitrogen and hydrogen in organic matter; (c) multiple sulfur and oxygen isotope ratios of minerals; and (d) abundance relationships and isotopic compositions of redox sensitive metals (e.g., Fe, Mo, Cr, and rare earth elements). For example, the particular fatty acids measured in a sample can indicate which types of bacteria and archaea live in that environment. Another example are the long-chain fatty alcohols with more than 23 atoms that are produced by planktonic bacteria. When used in this sense, geochemists often prefer the term biomarker. Another example is the presence of straight-chain lipids in the form of alkanes, alcohols and fatty acids with 20-36 carbon atoms in soils or sediments. Peat deposits are an indication of originating from the epicuticular wax of higher plants. Life processes may produce a range of biosignatures such as nucleic acids, lipids, proteins, amino acids, kerogen-like material and various morphological features that are detectable in rocks and sediments. Microbes