Today, I came across the discovery of a chiral pair of molecules in interstellar space. I know that a chiral molecule is a molecule that is not superimposable on its mirror image. But why is this discovery such a big deal? I think that the existence of chiral pairs should be obvious where multiple molecules exist. So why is this discovery significant?
The story is a big deal because it might help explain why molecules in living creatures have a single chirality
One of the great mysteries of living systems is that, when they use chiral molecules, they only use molecules of one chirality. There is no obvious mechanism to kick-start this preference and, while there are many esoteric theories, there is very little evidence that explains why one chirality was chosen over another.
Proteins are, for example, made from amino acids which are almost all chiral. And they are all left-handed (technically they are all levorotatory, see wikipedia). Most sugars used in biological systems are right-handed. There are simply no convincing theories that explain the origin of this preference.
One modern theory suggests that there is a subtle energetic preference for one chirality caused by the interaction of molecules with the electrons emitted in certain types of radioactive decay (the weak nuclear force involved in radioactive decay is one of the few fundamental forces to have a mirror-image preference). But other experts think the preference is arbitrary.
Resolving this would be big news for biology.
The reason why the observation of chiral molecules in space (the news story only reports the observation of a molecule that is chiral not that we can observe the chiral preference) is that it creates hope than we can observe directly whether the chiral preferences of life are inherent in the universe or are arbitrary.
We don't yet know whether propylene oxide (the molecule in the news story) exists with more of one chirality than the other, but now it has been observed, we can expect to find out as instruments improve. So the big story is that we now have some hope that we can test some of the theories about why life has a handedness preference.
I believe that this is the news article in question (link).
The fact that there are left and right versions in space makes sense. The ability to see the chirality in space might be a first... the technology/ability to see chirality might lead to finding life out there because life is preferential toward one chirality or another DNA and many sugars are right handed molecules in life (on earth); proteins are left handed. the "reason" for selective chirality of life is basically unknown.