Researchers propose a way to recognize a form of life that does not yet exist: “mirror life.”
Look at your two hands. They have the same elements, but it is impossible to superimpose them perfectly: the thumb is not on the same side. Some molecules work in the same way. They can exist in two nearly identical forms, one being the reflection of the other.
Life on Earth makes very precise choices between these two forms. Our proteins are notably built with amino acids of one type, while our DNA uses sugars of the other type. Hypothetical mirror life would make the opposite choices. It would be made of molecules resembling ours, but oriented in the other direction.
Why try to detect it? Some scientists fear that a mirror organism, if one were ever created, could evade ordinary biological defenses or interact unpredictably with living organisms today.
Researchers from the universities of Strathclyde and Durham, in the United Kingdom, have therefore considered a way to recognize it. Their idea relies on a property of light: it can be circularly polarized, meaning that its electric field rotates in one direction or the other as it propagates.
The team proposes using fluorescent molecules during the creation of this mirror organism, which would attach themselves to different parts of a cell, such as its membrane or genetic material. Once illuminated, they would emit light whose certain properties could reveal the organization of the molecules to which they are attached.
A single measurement would not be enough. The researchers propose combining several markers, each examining a different part of the cell. The set of signals would then form a kind of light signature, which could help distinguish an ordinary cell from its mirror equivalent.
The advantage is that instruments capable of measuring this type of light already exist. Some work with microscopes or cameras.
The researchers present a theoretical method here, which has not yet been validated as a complete test. They first propose developing this approach with ordinary cells, in order to have a tool if such monitoring ever became necessary.