Exotic grains of dust collected high above Earth are older than the Solar System and represent some of the most primordial material ever studied.

Few traces remain of the gas and dust that built the planets. But Hope Ishii at the University of Hawaii at Manoa in Honolulu and her colleagues analysed two ancient particles of interplanetary dust, gathered by NASA aircraft flying through Earth’s stratosphere. Inside the particles’ glassy mineral grains, the scientists found organic carbon. This discovery was surprising — organic matter should have broken down in the heat of the dense, swirling disk of material that formed the planets more than 4 billion years ago.

The survival of the organic carbon implies that the grains formed in the cold expanse of space before the Solar System existed — and therefore are the same stuff as the original building blocks of the planets.