Kuiper Belt Dust Suggests Heavy Oxygen in Outer Solar System

An examination of 12 interplanetary dust particles supports the longstanding but hard-to-prove theory that the Kuiper Belt is home to a reservoir of water that's rich in "heavy" oxygen. Scientists have suspected that ice in the outer solar system contains heavy oxygen – non-radioactive stable isotopes of the element. Yet, whether such a cache of heavy oxygen-enriched water truly exists has proven difficult to determine; meteorites rarely arrive with clues about this mystery. Now Lindsay Keller and colleagues have circumvented the need for meteorite samples altogether. They examined interplanetary dust particles collected from Earth's stratosphere, observing that the dust had high densities of scars from solar energetic particles – proving that the dust came from the Edgeworth-Kuiper Belt. Further analyses showed that dust particles were mainly made of hydrated minerals. Using models, Keller et al. investigated how these minerals could have formed, linking their existence to reactions with carbon dioxide and ice at low temperatures. The isotopic compositions of the minerals indicated that the water present in these reactions was made with one of two heavy oxygen isotopes, rather than normal oxygen. The evidence, the authors write, provides "compelling evidence for the presence of a major heavy water reservoir beyond the orbits of the gas giant planets that was largely isolated from inner solar system materials."