Scientists find evidence that an asteroid contains tryptophan

Tryptophan is the essential amino acid behind it. thanksgiving legend The idea that eating turkey can make you sleepy has been found to be found in Bennu, a small asteroid that passes by our planet about once every six years.

The discovery stems from an unprecedented sample collected by NASA’s OSIRIS-REx mission, which landed a spacecraft on the asteroid in 2020, capturing 4.3 ounces (121.6 grams) of rock and dust and landing it safely on the asteroid. came back The cache will be sent to Earth in 2023. NASA has since distributed a small portion of this sample to researchers around the world for analysis.

Studying Bennu is important because its composition mirrors that of the early solar system and gives scientists an insight into the beginnings of life. Previous research on bennu samples had found 14 of the 20 amino acids from which all living organisms on Earth derive, as well as all five biological nucleobases, the components that make up the genetic code in DNA and RNA.

Researchers had previously detected amino acids in samples taken from another asteroid. RyuguMeteorites collected by the Japan Aerospace Exploration Agency in 2019, as well as various meteors that fell to Earth. According to experts, growing evidence shows that asteroids may have delivered basic life components to our planet early on.

Now, a new analysis of Bennu samples has confidently, though not yet conclusively, identified tryptophan, increasing the number of protein-forming amino acids in the asteroid to 15 out of 20.

“Finding tryptophan on the asteroid Bennu is a big deal because tryptophan is one of the more complex amino acids and has never been seen in any meteorite or space samples before,” said José Aponte, an astrochemist at NASA’s Goddard Space Flight Center Astrobiology Analytical Laboratory. He co-wrote to work According to findings published Monday in the journal PNAS.

The presence of tryptophan on an asteroid supports the idea that the recipe for life may not have started only on Earth: “Seeing it occur naturally in space tells us that these ingredients were already produced in the early Solar System. This would have facilitated the start of life,” Aponte added in an email.

puzzle pieces

Bennu, whose name refers to an ancient Egyptian god associated with the sun, creation and rebirth, stretches for about a third of a mile. The space rock likely represents a piece that broke off from a much larger asteroid between 2 billion and 700 million years ago. It probably formed in the main asteroid belt between Mars and Jupiter, and its chemical composition reflects the beginnings of the solar system, dating back approximately 4.5 billion years. According to NASA.

Asteroid orbiting near Earth approximately 1.75 million years. Data suggests it could hit our planet in 2182, potentially leading to a “global winter.” Scientists are currently predicting probability of impact 1 in 2,700 or 0.037% chance.

Originally, the material that formed Bennu came from supernovae, explosions of ancient stars that occurred long before the formation of the solar system. The extreme heat of the explosions served as a forge, cooking the elements contained within the asteroid; The asteroid then withstood more heat from the collision that formed Bennu, as well as radiation from the sun, further altering the elements within it. Bennu has also been found to contain ammonia, a chemical that helps form molecules such as amino acids as well as different types of minerals, providing many of the ingredients needed to form the building blocks of life, but not life itself.

“They’re like puzzle pieces that haven’t been put together yet,” said Angel Mojarro, a postdoctoral researcher and organic geochemist at NASA’s Goddard Space Flight Center Astrobiology Analytical Laboratory and first author of the new study. “What this tells us is that many of the building blocks of life can be produced naturally within asteroids or comets, and the discovery of tryptophan expands the alphabet of amino acids that can be produced in space and delivered to Earth.”

Total 33 amino acids They have been found on Bennu before, but only 14 of them are used by living organisms on Earth to create proteins. Tryptophan will join the second group; It also belongs to the category of amino acids that scientists call essential because the human body cannot produce them and they must be obtained through the diet.

Mojarro added that further testing is needed to confirm the presence of tryptophan in the Bennu sample analyzed for the study, which weighed only 50 milligrams. However, given the pristine condition of the Bennu samples, it is likely that the find is not a result of terrestrial contamination, according to George Cody, a scientist at the Carnegie Institution for Science in Washington, D.C. Cody was not involved in the study, but worked on Bennu samples.

“I believe these molecules are legitimately derived from the asteroid Bennu,” Cody wrote in an email.

By collecting samples from the asteroid itself, researchers did not have to deal with damage from atmospheric entry, which changed the chemistry of asteroids that landed on Earth and made Bennu a much more reliable “time capsule” for the composition of the early solar system.

“Because OSIRIS-REx returns these samples intact, we end up seeing the fragile salts, minerals and organic matter that the meteorites lost upon entry,” said Dante Lauretta, professor of planetary science and cosmochemistry at the University of Arizona, Tucson, who is also one of the authors of the new study.

“Bennu’s main body was a geological world rich with multiple fluid systems operating in different places and at different times, each operating its own chemistry,” added Lauretta. “Bennu preserves a collection of different chemical systems, and together they indicate that the small bodies were dynamic, organically rich systems long before life emerged on Earth.”

Molecular ‘fossils’

Cody said this paper adds to scientists’ understanding of what molecules essential for life might be found in extraterrestrial materials. He added that if the natural chemistry that occurred at the dawn of our solar system produced the same molecules that life uses now, then there must be a connection between them.

The late Harold Morowitz, a pioneer in the study of the origin of life, believed that the molecules that form the nuclei of living organisms could be molecular “fossils” from the beginning of the solar system, and Cody explained that the identification of tryptophan and other protein-forming amino acids in the Bennu samples adds weight to this idea.

The discovery of tryptophan on Bennu further expands the remarkable diversity of compounds we now know can come from space, Kate Freeman, the Evan Pugh Professor at Penn State University, said in an email. “Asteroids were Earth’s first shopping delivery service, providing rich molecules to our prebiotic world,” added Freeman, who was not involved in the study.

The new research also highlights how important sample return missions are, according to Sara Russell, professor of planetary sciences and leader of the Planetary Materials Group at the Natural History Museum in London, who was not involved in the study. Although scientists have thousands of rocks from space in the form of meteorites in laboratories, they also need uncontaminated, pristine materials brought to Earth by space missions to get the full picture, he said.

Russell added: “The discovery of tryptophan in particular is surprising because we don’t see it in meteorites, perhaps because it cannot survive falling through the Earth’s atmosphere and hitting the Earth.”

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