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

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A team of scientists analyzed a rock in a laboratory, seeking to find some answers to humanity's greatest and most enduring questions.

the molecules that build proteins?

However, what they discovered threw them a curve. Instead of confirming one of the leading theories - that the early solar system mostly contained left-handed particles, which brought those components to the primitive Earth - it showed no bias at all.

I have to be honest, I was a bit let down," Glavin said. "It seemed like this dismissed 20 years of work by our lab and my entire career.

It's like a left and right hand: They're similar, but if you stacked them, the thumbs would be pointing in opposite directions.

On Earth, amino acids are consistently "left-handed," while sugars, a key part of DNA's structure, are always "right-handed," creating a distinctive rightward twist in the double helix. The uniformity of left-handed amino acids and right-handed sugars is puzzling to scientists, given that both left and right-handed versions of these molecules exist in equal amounts in nonliving chemical mixes.

Do you turn left? Did the preference for left-handed amino acids originate in the universe, or did it develop here on Earth?

A fundamental question for all of us is whether the fact of life had to be the way it is," said Iris Chen, a professor of chemical and biomolecular engineering at the University of California, Los Angeles, who wasn't involved in the asteroid research. "Is the universe inherently suited to our kind of life, or is our biology the result of random events and chance?

and planets.

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Honestly, I was a bit disheartened or let down. I felt that this undermined almost two decades of study in our lab and everything I've dedicated my career to.

The development of the very first cells remains a mystery, leaving the path to further evolution a topic of ongoing exploration.

If the comets from our solar system's "time capsules" contain more left-handed amino acids than right-handed ones, it could indicate that extraterrestrial objects may prefer left-handed molecules. If this is the case, rather than considering it a coincidence, it's possible that polarized light in space might have played a role in favoring the formation of left-handed molecules, giving them a slight advantage that amplified over time to create a larger disparity between the two types.

believes there may be another explanation for Bennu's departure from the norm.

"Bennu is an example of a type of meteorite that's too delicate to withstand hitting Earth and therefore is not really part of our collections," Dworkin said.

Perhaps the truth is that the design of life was decided by a random flip of a coin. Once an effective pattern had been established, it continued through evolution. The tiny machines inside cells, known as proteins and enzymes, fit together like a puzzle piece. If life had begun with right-handed amino acids, a switch to left-handed amino acids later might have brought everything to a halt. There are many benefits to uniformity: If humans used right-handed amino acids, they wouldn't be able to eat and digest foods that contain left-handed amino acids from plants or animals.

Scientists create synthetic right-handed amino acids in a lab. They function somewhat similarly, but are more difficult to break down. The enzymes that usually cleave them are rendered ineffective.

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Despite Glavin's disappointment that Bennu didn't show a chirality bias, the research is getting underway. He and his colleagues will study even more samples of the asteroid to check the handedness of additional amino acids.

A mix of both types found in an extraterrestrial sample would indicate that molecules were produced through chemical reactions without the need for life. However, a predominance of either type might be evidence of the presence of alien life.

Honestly, it might actually make finding life easier in certain situations because we wouldn't have to worry about the possibility of incorrect positive results," said Glavin. "We could think that if there's an increase in one or the other, there might be biology behind it.

on Microsoft Start.