The asteroid Bennu, recently sampled by NASA's OSIRIS-REx mission, has sparked intriguing theories about its origins.
Among these theories is the surprising possibility that Bennu many have originated from a water world, a hypothesis that emerged after scientists analyzed the sample of rock and dust - collectively known as regolith - collected from the asteroid in 2020. This mission marked a historic achievement as it was the first time an asteroid had ever been sampled by NASA.
The OSIRIS-REx spacecraft successfully extracted and transported the sample, weighing 4.3 ounces (121.6 grams), across 200 million miles back to Earth. Scientists had high hopes that this sample would unlock secrets about the solar system's early days and offer insights into the prebiotic chemistry that could have contributed to the emergence of life on Earth. The initial analysis of the sample, published in Meteoritics & Planetary Science, has indeed revealed fascinating findings that may help piece together the puzzle of our solar system's ancient history.
The OSIRIS-REx Sample Analysis Team found that Bennu's regolith contains essential compounds that form the foundation of biochemistry for all known life on Earth today. Specifically, the sample is rich in carbon and nitrogen, as well as organic compounds, all of which are critical to life as we understand it.
This discovery offers a rare glimpse into the conditions that existed over 4.5 billion years ago, during the formative years of our solar system. Remarkably, the rocks in Bennu's sample have preserved their original state without having melted or resolidified since their formation, providing strong evidence of their ancient origins.
However, one of the most surprising aspects of the sample was the presence of magnesium-sodium phosphate. This compound had not been detected in the remote sensing data collected by the spacecraft during its mission at Bennu, making its discovery within the sample particularly unexpected. The presence of magnesium-sodium phosphate suggests that Bennu may have originated from a small, primitive ocean world that no longer exists.
"The presence and state of phosphates, along with other elements and compounds on Bennu, suggest a watery past for the asteroid," stated Dante Lauretta, co-lead author of the paper and principal investigator for OSIRIS-REx at the University of Arizona, Tucson.
He added, "Bennu potentially could have once been part of a wetter world. Although, this hypothesis requires further investigation."
The idea that Bennu might have splintered off from an ocean world is particularly intriguing given recent astronomical discoveries. For instance, scientists working with the James Webb Space Telescope recently identified what they believe to be an ocean world, designated K2-18b, which is located 120 light-years away from Earth in the constellation Leo.
This distant planet orbits within the habitable zone of a red dwarf star named K2-18. K2-18b is believed to be 8.6 times larger than Earth and has shown an abundance of methane and carbon dioxide in its atmosphere, coupled with a notable shortage of ammonia. These chemical signatures support the hypothesis that there may be a water ocean beneath K2-18b's hydrogen-rich atmosphere.
K2-18b is classified as a "sub-Neptune" planet, a term used to describe planets that share characteristics with Neptune but are smaller in size. Sub-Neptunes are considered by some scientists to be the most common type of rocky exoplanet in the universe. The possibility that Bennu originated from a similar type of watery world expands our understanding of the diversity of celestial bodies and their potential to harbor life, or at least the building blocks of life, across the cosmos.
The discovery of such a link between Bennu and a possible water world not only raises new questions about the asteroid's history but also about the broader processes that shape the formation of planets and other celestial bodies. It hints at the possibility that the building blocks of life could be more widespread in the universe than previously thought, carried across the cosmos by ancient bodies like Bennu.
As scientists continue to analyze the sample from Bennu, further studies will be crucial in determining whether the asteroid indeed originated from a water world. These investigations will help refine our understanding of the early solar system and the origins of life, shedding light on the intricate and interconnected history of the cosmos.