NASA scientists want to solve a mystery: Why did life "turn left?"
When NASA launched a spacecraft to an asteroid, scientists patiently waited for their chance to look at bits of the space rock in a laboratory, hoping it would answer some of humanity's most enduring questions. For Danny Glavin, a senior sample scientist, he wanted to solve a relentless mystery in his life's work: Why are all known living things only based on the left-handed forms of amino acids, the molecules that build proteins? His moment arrived nearly a decade later. Glavin and a team of researchers probed the grit from Bennu, a carbon-rich asteroid made of loosely bound boulders, but what they found threw them a curveball. Rather than supporting one of the leading hypotheses — that the early solar system favored the left-handed variety and brought those ingredients to primitive Earth — it showed no favoritism at all. "I have to admit, I was a little disillusioned or disappointed," Glavin said. "I felt like this invalidated 20 years of research in our lab and my career." SEE ALSO: NASA's asteroid sample reveals key chemistry that could lead to life Researcher Jason Dworkin holds up a vial containing a Bennu sample. Credit: NASA / James Tralie Many amino acids, whether they're used in biology or not, come in two mirror-image forms. Each molecule has a central carbon atom with other atom groups attached, oriented in one direction or the reverse. This property, called chirality, is like a left and right hand: They're similar, but if you stacked them, the thumbs would be hitchhiking opposite ways. In Earth life, the amino acids are always "left-handed," and sugars, which partly make up the backbone of DNA, are always right-handed, giving the double helix its signature twist to the right. The homogeneity found among both is especially confounding to scientists because the left and right-handed versions of all these molecules are equally available in nonliving chemical mixes. Practically speaking, if all biological molecules took the reverse form, that might work jus
NASA scientists want to solve a mystery: Why did life "turn left?"