Ever wondered how do we test that there's life existence on other planets? We at Project Kratos are up with the second post of our wonderful series: How To Train Your Rover
Today we will talk about how can bio-markers play a significant role in detecting extra terrestrial life. What are Bio-Markers? Where and how do Astrobiologists look for life? And we will be answering the common questions that a common reader might have.
What is a biomarker?
The first question that comes to the mind is, “ What is a biomarker?”
A biomarker (or biosignature) is any substance – such as an element, isotope, or molecule – or phenomenon that provides scientific evidence of past or present life. A biosignature can provide evidence for living organisms outside the Earth and can be directly or indirectly detected by searching for their unique byproducts.
How to identify a biomarker ?
To look for biosignatures, the astrobiologists look for the following as an area of interest:
Isotope patterns: Isotopic evidence or patterns that require biological processes.
Chemistry: Chemical features that require biological activity.
Organic matter: Organics formed by biological processes.
Minerals: Minerals or biomineral-phases whose composition and/or morphology indicate biological activity (e.g., biomagnetite).
Microscopic structures and textures: Biologically formed cement, microtextures, microfossils, and films.
Macroscopic physical structures and textures: Structures that indicate microbial ecosystems, biofilms (e.g., stromatolites), or fossils of larger organisms.
Temporal variability: Variations in time of atmospheric gases, reflectivity, or macroscopic appearance that indicate the presence of life.
Surface reflectance features: Large-scale reflectance features due to biological pigments, which could be detected remotely.
Atmospheric gases: Gases formed by metabolic and/or aqueous processes, which may be present on a planet-wide scale.
Techno signatures: Signatures that indicate a technologically advanced civilization
Examples of biomarkers
Nucleic acids (DNA, RNA)
These would be a nearly unambiguous signature of extant life since there are no known examples of the abiotic production of linear ionic polymers with the complexity of DNA or RNA. They are the informational macromolecules involved in protein synthesis.
Proteins are macromolecules composed of one or more chains of amino acids. Proteins are extremely important biomarkers for life detection since they play important structural and metabolic roles in living organisms. Their presence would strongly indicate the presence of a life form.
Lipids are essential for life to exist. They play many important roles in maintaining the health of an organism. Arguably the most important function lipids perform is as the building blocks of cellular membranes. Other functions include energy storage, insulation, cellular communication and protection and therefore it is an important biomarker.
Carbon monoxide has been considered by many researchers as an anti-biosignature, i.e. its presence indicates an absence of life. The widely accepted reason for this is reactivity of CO, which can be oxidized or reduced by microbes and microbe like organisms. Hence, finding high amounts of carbon monoxide in the atmosphere may indicate absence of life.
Want to know more? Here are some interesting resources:
Textbook: Astrobiology - A very short introduction by David Catling.
Television Show: Cosmos - Possible Worlds
Coursera: Astrobiology and the search for extra terrestrial life by University of Edinburgh.
Author: Devansh Dixit