Discovering Life’s Origins and the Mystery of Homochirality

At a recent meeting of the American Astronomical Society, a team of astronomers announced their discovery of the first chiral molecule outside of our solar system. Their exciting findings, published last week in the journal Science, could bring us closer to a stronger understanding of one of life’s great mysteries: the specifics of how life on Earth came to develop.

Chirality is a molecular property that describes molecules that exist in one of two chemically identical but structurally mirrored states. Scientists often describe these mirrored states as being either left-handed or right-handed for referencing purposes. The molecules necessary to form life here on earth are chiral molecules that exist predominantly in either the left-handed state or the right-handed state. No one knows why the building blocks of life tend to prefer one state over the other.

Given the abundance of chiral molecules here on Earth, it would stand to reason that there would be equal or nearly equal amounts of each mirrored state. However, what we find is that only one state exists within life on earth, a state known as homochirality. For instance, the amino acids that make up proteins are all left-handed chiral molecules. These amino acids form together to make up proteins, which are the basic building block of all living things. Life’s preference for the left-handed chiral molecules has puzzled biologists for a long time.

That’s where this discovery becomes important. The discovery of the complex chiral molecule propylene oxide (CH₃CHOCH₂) within a gaseous cloud outside our solar system has the potential to shed some light on Earth’s homochiral mystery. By observing these clusters of chiral particles at the center of the Milky Way galaxy, we can witness the process by which chiral molecules are formed within gaseous clouds and how one mirrored state of these chiral particles comes to overwhelm the other state.

From this, we can begin to deduce why life chooses one particular molecular orientation over the other and what makes that particular chiral state—either left-handed or right-handed—beneficial to the formation of life. In addition to publishing the findings, Science simultaneously released a video to help explain the phenomenon of chiral molecules and why this discovery is important to understanding how life came to be on Earth. To learn more, watch their video below: