After analyzing ten years of data from the Cassini spacecraft that’s been orbiting Saturn since 2004, a team of scientists led by Nicolas Altobelli of the European Space Agency in Madrid, Spain, reports finding dust that came from outside our solar system. Along with millions of ice-rich dust particles shed by Saturn’s moons, Cassini’s Cosmic Dust Analyzer detected a grand total of 36 grains that the scientists could trace back to the local interstellar cloud. That cloud is an almost empty bubble of gas through which our solar system is currently moving.
The small interstellar dust grains were zipping past Saturn at speeds of over 72,000 kilometers per hour (44,000 mph), which explains how they avoided becoming gravitationally trapped by the sun. This marks the first time scientists have been able to analyze material from outside our solar system. Intriguingly, the Cassini Cosmic Dust Analyzer saw the same kind of chemical and mineralogical make-up in the interstellar grains as it did in the local dust.
Confirmation that material from outside the solar system does in fact reach us may revive the ancient idea of panspermia. In the early 20th century Svante Arrhenius, a Swedish physical chemist, suggested that bacterial spores propelled through space by radiation pressure could seed other planets with life. This proposed mechanism of panspermia was rejected by the scientific community, because it was shown that bacterial spores could not survive space radiation, particularly ultraviolet radiation, for long time periods. Later studies, however, showed that bacterial spores could survive if they were covered by some dust material, or were inside a meteorite.
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