NASA
Asteroid Bennu
It was already known that Bennu carried all but one of the molecules needed to start life. Researchers have just found the missing ingredient: sugar. Another study discovered a molecule vital to happiness on the asteroid.
A study this Tuesday in Nature Geoscience revealed that all the essential ingredients to start life as we know it have now been found in samples from the asteroid Bennu… even sugar.
In 2020, NASA’s OSIRIS-REx mission extracted samples from Bennu, an asteroid that was orbiting the Sun hundreds of millions of kilometers away, between Mars and Jupiter. The mission returned the samples to Earth in 2023.
Since then, small amounts of the 121 grams collected have been sent to laboratories around the world for analysis, so that experts in detecting each type of biological compound can get to work.
Early studies revealed the presence of water, carbon and several organic molecules. Then came the detection of amino acids, formaldehyde and all five of the nucleobases found in RNA and DNA, as well as phosphates.
However, this is not enough to assemble the molecules that carry genetic information. The rungs of the RNA and DNA ladder contain a sugar, which is ribose in RNA and deoxyribose in DNA – and this was missing in early analyzes of the Bennu material.
Now, researchers at Tohoku University in Japan have revealed the presence of ribose, as well as other sugars, including lyxose, xylose, arabinose, glucose and galactose – but not deoxyribose.
As New Scientist reports, the new work shows that asteroids could actually have provided all the ingredients necessary for life on Earth. It also supports the RNA world hypothesis for the origin of life because ribose was found but not deoxyribose.
This idea proposes that the earliest form of life on Earth, long before the appearance of cells or DNA-based life, consisted of RNA molecules that contained genetic information and could replicate.
Vital molecule for happiness
Another analysis of Bennu material, carried out on the sidelines of a study in October in PNASclaims to have discovered, on the asteroid, tryptophan – a critical nutrient used to produce the neurotransmitter serotonin, which influences mood.
Tryptophan is one of the nine essential amino acids that the human body cannot produce on its own. If its detection on Bennu is confirmed, it would mark the first time ever found in an extraterrestrial sample.
Researchers from NASA and the University of Arizona examined pulverized fragments of the asteroid, testing the 20 amino acids that build protein in the body (nine of which the body cannot produce and must obtain from food), as well as the five common nucleobases that encode our genetic instructions (adenine, guanine, cytosine, thymine and uracil).
The analysis confirmed the presence of the 14 amino acids detected in a previous study, as well as the nucleobases. They also found several non-biological amino acids and nucleobases, confirming the extraterrestrial origin of the molecules in the samples.
To their surprise, the researchers also detected the tryptophan signal – faint, but present in multiple portions of a Bennu sample.
Importance of tryptophan
The brain uses tryptophan to produce serotonin, the neurotransmitter that helps, among other functions, regulate mood and feelings of well-being and happiness. People with low serotonin are prone to depression and anxiety.
The amino acid is relatively fragile, making it unlikely to survive inside a meteorite that falls to Earth in an atmospheric entry flare. This may explain why it has never been found in meteorite samples to date.
“Additional analyzes targeting tryptophan using other techniques capable of measuring its enantiomeric and isotopic compositions are needed to firmly establish its origin in Bennu and possibly other astromaterials,” the researchers warned.
