NASA scientists want to solve a mystery: Why did life “turn left?”

rock in a laboratory, hoping it would answer some of humanity’s most enduring questions.

, the molecules that build proteins?

, 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.”

, 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.

to turn left? Did the bias toward left-handed amino acids begin in the cosmos, or did it happen later on this planet?

“A fundamental question for all of us is whether life had to be the way it is,” said Iris Chen, professor of chemical and biomolecular engineering at UCLA, who wasn’t involved in the asteroid study. “Is the universe predisposed to our kind of life, or is our biology the result of accidents and chance?”

and planets.

.

“I have to admit, I was a little disillusioned or disappointed. I felt like this invalidated 20 years of research in our lab and my career.”

to form the first cells. The rest is evolution, perhaps.

, the solar system’s time capsules, would also reveal more left-handed amino acids. If the solar system indeed harbors more lefties, perhaps polarized light in space was the culprit. A slight favoritism in the environment could turn into a larger disparity over time.

, thinks there may be a different reason for Bennu bucking the trend.

“Bennu is an example of one type of future meteorite which is too fragile to survive landing on Earth, and so it’s not really in our collections,” Dworkin said.

Maybe the reality is that life’s design was determined by a coin flip. Once a successful pattern was established, the template continued through evolution. Proteins and enzymes, tiny drivers inside cells, fit together like a jigsaw puzzle. If life emerged with left-handed amino acids, switching to right-handed amino acids later might have stopped everything from working. There are vast advantages to uniformity: If people were based on right-handed amino acids, they wouldn’t be able to eat and digest plants or animal products based on left-handed amino acids.

with right-handed amino acids in a lab. They function similarly, but they’re much harder to destroy. Enzymes that would typically break them down are rendered useless. Like your hair dryer on an international vacation, the tool won’t work if the plug and outlet don’t match.

.

Despite Glavin’s disappointment that Bennu didn’t present a chirality bias, the research continues. He and his collaborators plan to study more samples of the asteroid to investigate other amino acids’ handedness.

. An even mix of both types in an extraterrestrial sample might suggest molecules were made chemically without the involvement of living things. But an excess of one type could be a clue for alien life.

“Frankly, it actually might make the search for life easier in some respects because we don’t have this risk potentially of a false positive,” Glavin said. “We (could) believe that if there’s an amplification of one or the other, that there may be biology behind it.”

on Microsoft Start.