What if There’s a “Mirror Version” of Life Hiding on Earth?
Astrobiologists and scientists are both interested in finding out where life came from and what other possibilities there are. One interesting idea that has caught their attention is the idea of “mirror life.” The chemical handedness of living things on Earth determines how they normally behave. For example, amino acids tend to be left-handed (L-amino acids), while sugars tend to be right-handed (D-sugars). This bias is so deeply rooted in our biology that it makes us wonder if there are other types of life that are based on the opposite chirality? This is what we might call “mirror life.”
What does Mirror Life mean?
“Mirror life” refers to made-up living things whose genes are exact copies of those found in normal life on Earth. This time, they would use D-amino acids instead of L-amino acids and L-sugars instead of D-sugars. At first glance, these living things would look a lot like living things we know today, but their metabolic processes and how they work with normal biochemistry would be completely different. In the end, this could lead to living things that are very similar to normal life to our eyes but very different at the molecular level.
Why Think About Mirror Life?
Second Genesis on Earth: One reason scientists are excited about the idea of mirror life is that it could be a “second genesis” of life right here on Earth, a completely different branch that started before our known environment. Finding even a single example of this kind of life would change the way we think about the variety and origins of biology.
Testing the Universality of Biochemical Homochirality: All known living things have the same molecular handedness, but no one knows for sure if this is a trait that all living things share. If mirror life exists, it would be a challenge to the idea that homochirality is unavoidable. This would mean that the chemistry of life is more flexible and changeable than was thought before.
Implications for Astrobiology: The search for life beyond Earth often focuses on biochemical signs that we know. When we think about the chance of mirror life, our standards have to get bigger. Our present tools for finding life might miss it if it evolved with the opposite chirality in a different place. Figuring out what kinds of things mirror life might have can help future missions that explore other worlds and moons.
New developments and research efforts
Scientists are taking the idea of mirror life very seriously, as shown by recent news stories and study projects. According to a Dec. 12, 2024 story in the New York Times, scientists are looking for mirror-image microbes in Earth’s most extreme environments, like deep underground habitats or lakes that are very acidic. These niches may have given mirror life the chance to develop on its own and stay away from more common organisms.
In the December 2024 issue of Nature, researchers describe how they plan to do experiments to find mirror-oriented amino acids or sugars in natural samples. These efforts depend on advanced spectroscopic and high-precision chromatography techniques that can tell the difference between molecular enantiomers, which are the right-handed and left-handed forms of the same substance.
On the other hand, a CNN story from December 16, 2024, talks about how exciting and dangerous these discoveries are. Finding mirror life could bring up very important hygiene issues. If mirror microbes exist and we accidentally let them into areas where normal life is dominant, what might happen? Could they beat out known organisms, or would the fact that they don’t work with normal biology stop them from spreading?
References:
The New York Times (2024, December 12). Scientists Seek “Mirror Life” in Earth’s Hidden Corners. https://www.nytimes.com/2024/12/12/science/mirror-life-microbes-research.html
Nature (2024, December). In Search of the Universe’s Other Hand: The Hunt for Mirror Life on Earth. https://www.nature.com/articles/d41586-024-04223-2
CNN (2024, December 16). Mirror-Image Bacteria: Exciting Possibilities and Potential Risks. https://www.cnn.com/2024/12/16/science/mirror-bacteria-research-risks/index.html
Benner, S. A. (2010). Defining life. Astrobiology, 10(10), 1021–1030. https://doi.org/10.1089/ast.2010.0524
Bada, J. L. (1995). Origins of homochirality. Nature, 374(6524), 594–595. https://doi.org/10.1038/374594a0
Davies, P., & Lineweaver, C. H. (2011). Finding a second sample of life on Earth. Astrobiology, 11(10), 1005–1010. https://doi.org/10.1089/ast.2010.0590
Cleland, C. E. (2019). The Quest for a Universal Theory of Life: Searching for Life as We Don’t Know It. Cambridge University Press. ISBN:978-1108794929
Luisi, P. L. (2016). The Emergence of Life: From Chemical Origins to Synthetic Biology. Cambridge University Press. ISBN:978-1107150536
