A biosignature is an indicator of past or present life. Many different types of biosignatures have been proposed, but no single biosignature is definitive proof of life. Biosignatures can be divided into two main categories: direct and indirect. Direct biosignatures are physical signs of life, such as fossils or DNA. Indirect biosignatures are chemical signs that suggest the presence of life, such as oxygen in the atmosphere or methane in a planet’s atmosphere.
The search for extraterrestrial life is one motivation for the study of biosignatures. If scientists can identify what characteristics would be evidence for life on another world, they can design missions to look for those features. For example, the Mars Science Laboratory’s Curiosity rover is equipped with instruments that will help search for chemical signatures of Martian microbes.
Biosignatures are also important in astrobiology, the study of the origin, evolution, distribution and future of life in the universe. By understanding how different kinds of biosignatures form on Earth, astrobiologists can interpret them when they are found on other worlds. For example, stromatolites – structures formed by microbial mats – are thought to be some of the oldest fossil evidence for life on Earth. They have also been found on Mars and Jupiter’s moon Europa, providing clues about possible ancient Martian microbes and potentialEuropan Life forms respectively .
There is still much debate over what kind of evidence should be considered a biosignature. Some scientists argue that any sign that could be caused by living organisms should count as a potential biosignature (e..g., an anomaly in spectral data), while others believe that only unequivocal proof (e..g., fossils or DNA) should be considered true biosignatures . The definition may also change as our technology improves and we are able to detect smaller and smaller signs of past or present life . Regardless, research into biosignatures continues to provide new insights into both our own planet’s history and the possibility of finding extraterrestrial life elsewhere in the universe .