Propylene oxide and the start of life on Earth

In the post The Truth About the Apollo Lunar Samples we were introduced to the “lefty” and “righty” qualities of amino acids, on earth and in space. We learned why the Apollo Lunar Samples taken decades ago were found to have small quantities of amino acids that paralleled those found on Earth. But we did not explore why the “lefty” orientation of the majority of our amino acids on Earth came to be that way. Recent research has shed light on this question, with the discovery of propylene oxide.

Propylene oxide

A team of scientist at the National Radio Astronomy Observatory have recently discovered “the first complex organic chiral molecule in interstellar space”. A “chiral” molecule is one that has two orientations despite having the same components (like our left and right hands or feet). The molecule is called propylene oxide and was found near a huge cloud of dust and gas within our galaxy, called Sagittarius B2, or Sgr B2.

“This is the first molecule detected in interstellar space that has the property of chirality, making it a pioneering leap forward in our understanding of how prebiotic molecules are made in the Universe and the effects they may have on the origins of life”. – Brett McGuire, Chemist with the National Radio Astronomy Observatory (NRAO)

Why is this discovery significant? Well, while it is already known that chiral molecules could have come to Earth on a comet or meteorite, only the actual molecules themselves could give an indication as to how they became “lefties” or “righties”. Ultimately, finding out how they came to be left or right oriented would explain how we came to have the mostly “one-handed” molecules that support life.

“By discovering a chiral molecule in space, we finally have a way to study where and how these molecules form before they find their way into meteorites and comets, and to understand the role they play in the origins of homochirality and life,” McGuire said further. The next step is for scientists to determine how the propylene oxide came to have its current orientation, but that’s an answer to keep an eye out for in the future.

Resources for Educators: