An international study has established that two well-known asteroids — Ryugu and Bennu — have a common origin and are “sibling bodies” formed in an ancient cosmic collision.
According to the analysis, Ryugu and Bennu belong to the so-called Polana family — a group of asteroids formed in a powerful collision in the main asteroid belt between the orbits of Mars and Jupiter. Their “parent body” was an ancient carbon-rich asteroid about 55 km in diameter, belonging to the rare and oldest type, F. The shared origin was confirmed by unique “spectral fingerprints” — matching infrared data from all three asteroids, including Polana.
The differences in the composition of Ryugu and Bennu are explained by different levels of exposure to solar radiation after they left the original orbit. Samples from Ryugu contained uracil — a component of RNA, one of the key “building blocks” of life — while samples from Bennu contained phosphates, which may point to the existence of an ancient ocean on their progenitor. This reinforces the hypothesis that asteroids could have delivered to Earth the ingredients needed for life to emerge.
