NASA has made two major asteroid-related announcements this week, highlighting both the fascinating scientific potential of these celestial bodies and the importance of planetary defense. While researchers have unveiled groundbreaking discoveries from the samples collected from asteroid Bennu by the OSIRIS-REx mission, another team of astronomers has detected a newly discovered asteroid, 2024 YR4, which has a small chance of impacting Earth in 2032.
The asteroid Bennu. Credit: NASA
These two discoveries reinforce the dual nature of asteroids—offering valuable insights into the origins of life while also posing potential risks to our planet.
Asteroids are remnants from the formation of the solar system 4.5 billion years ago, making them invaluable time capsules for scientists studying the early solar system and the origins of life. The OSIRIS-REx spacecraft, launched in 2016, was tasked with retrieving samples from Bennu, a near-Earth asteroid rich in carbon-based materials. In October 2023, the spacecraft successfully returned 121.6 grams (4.29 ounces) of pristine asteroid material to Earth—exceeding NASA’s original goal of collecting at least 60 grams.
Now, researchers from NASA’s Goddard Space Flight Center, the Smithsonian Institution, and London’s Natural History Museum have analyzed a portion of these samples, publishing their initial findings in the prestigious journals Nature and Nature Astronomy. Their results confirm the presence of 14 of the 20 amino acids essential for building proteins in life on Earth, as well as all five nucleobases that encode genetic instructions in DNA and RNA. This discovery supports the theory that the fundamental ingredients for life were widespread throughout the early solar system.
Surprising Discoveries: Ammonia and Chirality
While the presence of amino acids was expected, one of the biggest surprises was the discovery of a high concentration of ammonia—100 times more than typically found in Earth's soils. Ammonia is a key component in the formation of amino acids and other organic molecules, and its abundance in the Bennu samples suggests that early asteroids may have played a significant role in delivering the
chemical building blocks necessary for life on Earth.
Many amino acids come in two mirror image versions, dubbed “left” and “right.” Life on Earth builds proteins almost exclusively from left-handed amino acids, but in the Bennu samples, left and right-handed amino acids exist in equal abundance. Credit: NASA Goddard/OSIRIS-REx
Another unexpected finding was the chirality—or "handedness"—of the amino acids in the sample. Life on Earth overwhelmingly relies on left-handed amino acids, a pattern also observed in meteorites, which are asteroid fragments that have fallen to Earth. Scientists had anticipated finding the same left-handed bias in the Bennu samples. Instead, they found an equal mix of left- and right-handed amino acids, a phenomenon known as a racemic mixture.
Danny Glavin, NASA’s senior scientist for sample return at Goddard, admitted that this result initially shook him. “I was a little disillusioned or disappointed because I felt like this invalidated 20 years of research,” he said. “But this is exactly why we explore.” The discovery raises new questions about how amino acid chirality developed in the solar system and whether life’s preference for left-handed molecules arose after these building blocks arrived on Earth.
Future Research and Preservation for Generations to Come
Scientists have analyzed only 0.06% of the returned material so far, meaning there are still many discoveries to be made. NASA has set aside 70% of the sample for future research, including 7.5 grams (0.26 ounces) that will be stored in a deep-freeze container for at least 50 years. This ensures that future generations of scientists, equipped with more advanced technology, will have the opportunity to study the Bennu samples and potentially make even greater discoveries.
This approach mirrors NASA’s strategy with the Apollo lunar samples. Some moon rocks collected during the Apollo missions were deliberately sealed for decades, allowing modern scientists to analyze them with tools far more sophisticated than those available at the time of their collection.
Asteroid 2024 YR4: A Potential Impact Threat in 2032
While the Bennu samples provide a glimpse into the past, another asteroid discovery has planetary defense experts looking to the future. On December 27, astronomers using the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Chile detected a new near-Earth asteroid (NEA), designated 2024 YR4. Within days, it was added to NASA’s Sentry risk list, which tracks asteroids with a possible impact risk.
Currently, NASA estimates that YR4 has about a 1% chance of colliding with Earth on December 22, 2032. While this probability is still low, it is the highest impact risk currently assigned to any known large asteroid.
Size and Potential Impact Consequences
YR4’s size is estimated to be between 130 and 300 feet (40–91 meters) in diameter. If it were to strike Earth, the impact could be significant.
Lindley Johnson, NASA’s former Planetary Defense Officer, compared the potential consequences to the Tunguska event of 1908, when an asteroid exploded over Siberia, flattening more than 2,000 square kilometers (770 square miles) of forest. At the lower end of YR4’s size estimate (40–60 meters), the impact would likely be similar to Tunguska. However, if the asteroid is closer to the 300-foot estimate, the consequences could be even more severe, particularly if it were to strike a populated area or the ocean, potentially triggering a localized tsunami.
Two international groups—the International Asteroid Warning Network (IAWN), led by NASA, and the Space Mission Planning Advisory Group (SMPAG), chaired by the European Space Agency (ESA)—are closely monitoring YR4.
While ESA estimates a 1.2% probability of impact, both agencies caution that such probabilities often change as new observations refine the asteroid’s trajectory. In many cases, an asteroid’s impact probability initially increases before additional data allows scientists to rule out a collision. However, if YR4 remains a significant concern next week, SMPAG will discuss potential response strategies during a United Nations Committee on Peaceful Uses of Outer Space (COPUOS) meeting scheduled for February 3-14 in Vienna, Austria.
Planetary Defense and Next Steps
NASA’s Planetary Defense Coordination Office (PDCO) is responsible for alerting the U.S. government about potential asteroid threats. Lindley Johnson, now NASA’s Planetary Defense Officer Emeritus, confirmed that the appropriate notifications have already been made. The asteroid’s trajectory is being updated daily, with the latest data available on NASA’s Center for Near-Earth Object Studies (CNEOS) and ESA’s Near Earth Object Coordination Centre (NEOCC) websites.
While YR4 will soon become unobservable as it moves behind the Sun, planetary defense experts will continue tracking it once it becomes visible again in a few months. Additional observations will help refine its orbit and determine whether it remains a genuine threat or if its impact probability drops to zero.
These two asteroid-related discoveries illustrate the complex relationship humanity has with these space rocks. On one hand, Bennu’s samples offer extraordinary insights into the early solar system, potentially answering fundamental questions about the origins of life. On the other, YR4 serves as a reminder that asteroids, while fascinating, can also pose real threats to Earth.
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