Researchers have identified tryptophan, an essential amino acid, on the asteroid Bennu, a significant finding that enhances our understanding of the origins of life. This discovery arises from the groundbreaking sample collection conducted by NASA’s OSIRIS-REx mission, which successfully returned a cache of materials from Bennu to Earth in 2023. Scientists believe that the presence of tryptophan, a compound often associated with the sleepiness some experience after consuming turkey, may indicate that the building blocks of life exist beyond our planet.
Groundbreaking Findings from Bennu
The samples collected from Bennu, which weighed approximately 4.3 ounces (121.6 grams), provide a unique glimpse into the early solar system, dating back about 4.5 billion years. Previous analyses of Bennu had already revealed 14 of the 20 amino acids essential to life on Earth, as well as all five biological nucleobases that constitute the genetic code in DNA and RNA. The recent identification of tryptophan increases the count of protein-building amino acids found on Bennu to 15.
José Aponte, an astrochemist at NASA’s Goddard Space Flight Center, coauthored a study published in March 2024 in the journal PNAS. He emphasized the significance of this finding, stating, “Finding tryptophan in the Bennu asteroid is a big deal, because tryptophan is one of the more complex amino acids, and until now it had never been seen in any meteorite or space sample.”
A Closer Look at the Asteroid’s Composition
Bennu, named after an ancient Egyptian deity associated with creation and rebirth, measures approximately 0.5 kilometers in diameter. It is believed to have formed in the main asteroid belt between Mars and Jupiter and has been orbiting near Earth for around 1.75 million years. With an estimated impact probability of 1 in 2,700 in the year 2182, understanding Bennu’s composition is critical not just for comprehending the origins of life but also for planetary defense.
Researchers suggest that the materials making up Bennu originated from supernova explosions, which forged the elements found in the asteroid. These elements underwent further alteration due to the heat from the impact that formed Bennu and radiation from the sun. The asteroid has also been found to contain ammonia and various minerals, contributing essential ingredients for the formation of life.
Angel Mojarro, a postdoctoral researcher and organic geochemist at NASA, highlighted the importance of these findings. “They’re like jigsaw pieces that are not yet assembled,” he remarked. “Finding tryptophan expands the alphabet of amino acids that are produced in space and could have been delivered to Earth.”
While the identification of tryptophan is a major milestone, further analysis is needed to confirm its presence in the 50 milligram sample analyzed. George Cody, a scientist at the Carnegie Institution for Science, underscored the reliability of the samples collected by OSIRIS-REx, stating, “I believe these molecules are legitimately derived from the Bennu asteroid.”
Overall, the research emphasizes the potential of asteroids like Bennu to deliver vital organic compounds to Earth, supporting the hypothesis that the ingredients for life may have been present in our solar system long before life emerged on our planet.
Kate Freeman, a professor at Penn State University, echoed these sentiments, stating that asteroids served as the early Earth’s “grocery delivery service,” providing a wealth of organic molecules necessary for prebiotic chemistry. This study is a testament to the importance of sample return missions, as they provide uncontaminated materials essential for understanding the origins of life on Earth.
As scientists continue to analyze the pristine samples from Bennu, the findings offer a tantalizing glimpse into the complex chemistry that may have paved the way for life as we know it.
