Chemtrails could reveal aliens unlike any life on Earth

A new method to recognize the chemical properties of living things could help us detect extraterrestrial life, even if it works differently than life on Earth.

In the search for extraterrestrial life, scientists typically rely on biosignatures—substances or patterns that can reliably indicate the presence of living organisms. Astronomers can analyze the atmospheres of distant planets to look for molecular biological signatures. But many molecules produced by living things can also be formed by geological or chemical processes in the absence of life forms.

A new test he invented Christopher Carr at the Georgia Institute of Technology and his colleagues, is based on amino acids. Amino acids are the building blocks of proteins, the complex molecules on which all life on Earth depends. However, amino acids are relatively simple molecules and can occur in the absence of life: for example, they have been found in lunar soil and on comets and meteorites.

So instead of just detecting amino acids, Carr and his colleagues reasoned that measuring the reactivity of molecules in a sample would be a more reliable indicator of living things.

In a nonliving system, molecules are formed and destroyed when they react with things in their environment, such as cosmic rays or other molecules, but the more reactive molecules are more likely to disappear. “If you don’t have a system in place to maintain what’s present, then the things that will tend to be destroyed will be the ones that are more reactive,” says Carr. However, living systems preferentially retain reactive molecules because they need them for the chemical processes that support life, resulting in a unique signature.

The reactivity of a compound is determined by the arrangement of electrons in the molecule. More reactive molecules have a smaller energy difference between the outermost electron and the next available space that would be filled by another electron during the reaction.

Carr and his team calculated this difference in energy for 64 amino acids, including many that are not used by life on Earth. They then looked up the abundance of amino acids in known samples that came either from abiotic sources such as meteorites or lunar soil, or from living samples such as fungi or bacteria, and used their molecular energy calculations to map the statistical distribution of amino acid reactivity. From this they could then assign a probability that the sample was alive or dead.

Using this method on more than 200 living and non-living samples, they found that it could correctly identify life 95 percent of the time. “The beauty of this approach is that it’s incredibly simple,” says Carr. “It’s very explainable and directly related to physics.”

Life, if it exists elsewhere in the universe, is likely based on carbon and amino acid chemistry and works by the same rules of chemical reactivity as life on Earth, Carr says, so this method should work for extraterrestrial life, he says. “Life absolutely needs to control when, how and where molecules interact and reactions take place, so this will involve structures that can regulate the flow of electrons and how things interact electrically,” says Carr.

Using the reactivity of molecules to detect life is not a new idea, but measuring reactivity in a statistical distribution is, he says Henderson Cleaves at Howard University in Washington DC. The method could form part of a life-detection toolkit on a future space mission to Mars or one of Saturn’s moons, such as Enceladus, but it would require equipment that can accurately measure the molecules and their abundance, which is not easy, Cleaves says.

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