Life’s left-handed puzzle: NASA discovers a bigger mystery surrounding our origins

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Envision a world where proteins could be constructed with molecules that are reflections of each other, similar to your right and left hands. Researchers have been pondering a long-standing question: Why does life rely exclusively on left-handed amino acids? A recent NASA study has now added a new twist to this captivating mystery.

on our planet.

"The research suggests that the eventual sameness of life's building blocks may not be due to a predetermined chemical process, but could have developed through the influence of later evolutionary forces," says Alberto Vázquez-Salazar, a postdoctoral scholar who contributed to the study, in a media release.

.

It's still a mystery what the first building blocks of life were, and figuring that out could be key to understanding how life started on our planet and even how it might exist elsewhere in space.

"Understanding the chemical properties of life helps us know what to look for in our search for life across our solar system," explains NASA scientist Jason Dworkin.

This mission collected samples from the asteroid Bennu and brought them to Earth in 2023. These samples likely contain remnants dating back to the solar system's formation about 4.5 billion years ago.

"We're studying samples from OSIRIS-REx to determine the handedness of individual amino acids, and future samples from Mars will also be examined in the lab for signs of life, including ribozymes and proteins," Dworkin explains.

itself.

Paper Summary

Methodology

Scientists experimented with how specific types of RNA, referred to as ribozymes, interact with amino acids that have varying "handedness" (like left-handed and right-handed gloves). They carried out studies using a blend of these amino acids and permitted the ribozymes to connect with them.

Afterward, they determined which type of amino acid each ribozyme was most compatible with. In simpler terms, ribozymes act as tiny tools that work effectively with specific molecules. This study was like presenting these tools with a choice between two possible options to see which molecule they could work with most efficiently.

Key Results

The study found that ribozymes do not consistently choose one "handedness" of amino acids over another. About half of them prefer right-handed ones, while the others favor left-handed ones. This discovery was surprising because it shows that there is no natural preference for ribozymes built right in. Instead, it depends on the particular design or group of the ribozyme in question. This suggests that the building blocks of life might not have had a strong preference for one-handedness over the other to start.

Study Limitations

The results are thought-provoking, however, they rely on a controlled laboratory environment that may not exactly replicate the conditions that existed on early Earth. The ribozymes evaluated were chosen from an artificial collection, implying they may not resemble the ribozymes that occurred naturally. Furthermore, this study centered on one particular type of chemical reaction and amino acids, so the findings may not be applicable to other scenarios or ecosystems.

Discussion & Takeaways

This research disputes the concept that a natural bias in RNA caused life's molecules, such as proteins, to develop a preferred side or handedness. It suggests that random factors or chance occurrences during the early stages of evolution might have played a role in determining this handedness. This new perspective reveals a range of possible paths that life could have taken, depending on the types of RNA structures present initially.

Funding & Disclosures

Funding for the study was provided by NASA, the Simons Foundation, and the National Science Foundation. The University of California also contributed through its fellowship programs. The authors confirm that they have no financial relationships that could influence the presentation of their findings or analysis.