Defining life is surprisingly challenging. While we intuitively recognize living organisms as having life, a precise definition remains elusive. Dictionaries offer various descriptions, such as the ability to grow, reproduce and respond to stimuli.

But, even these definitions can be ambiguous.

A more comprehensive definition considers life as a self-sustaining chemical system capable of processing information and maintaining a state of low entropy with little disorder or randomness.

Life elsewhere could use different elements as building blocks. Silicon, with its chemical similarities to carbon, has been proposed as a potential alternative.

If they exist, silicon-based life forms may exhibit unique characteristics and adaptations. For instance, they might use silicon-based structures for support, analogous to bones or shells in carbon-based organisms.

Even though silicon-based organisms have not yet been found on Earth, silicon plays an important role in many existing life forms. It is an important secondary component for many plants and animals, serving structural and functional roles. For example, diatoms, a type of algae found in the ocean, feature glassy cell walls made of transparent silicon dioxide.

This doesn’t make diatoms silicon-based life forms, but it does prove silicon can indeed act as a building block of a living organism. But we still don’t know if silicon-based life forms exist at all, or what they would look like.

This asymmetry in space-derived organic molecules is also observed in all biomolecules on Earth (proteins, sugars, amino acids, RNA and DNA), suggesting it could have arisen from the slight imbalance delivered from space, supporting the theory that life on Earth is extraterrestrial in origin.

The slight imbalance in chirality observed in many organic molecules could be an indicator that life on Earth originated from the delivery of organic molecules by extraterrestrial life. We could well be descendants of life that originated elsewhere.