Right place, right tools—Cassini spacecraft captures interstellar dust grains

An artist's conception of Cassini, which carries a dust analysis system. (credit: NASA)

The composition of the dust between stars in our galaxy provides a window into some of the material that went into forming our Solar System. The local dust left behind from this process has been through many shake-ups in its history that have changed its composition; interstellar dust should be relatively pristine. For a long time, however, our efforts to understand interstellar dust have relied largely on inferences, as it’s difficult to directly observe the dim, diffuse material using telescopes.

Luckily, there is a way to get a direct measurement. There’s a cloud of interstellar dust near our Solar System, known as the Local Interstellar Cloud (LIC, sometimes called the “Local Fluff”). Some of it is streaming into our Solar System. This stream of LIC material was first observed by the Ulysses spacecraft in 1993, and grains of dust were captured by the Stardust spacecraft in the early 2000s and analyzed by a citizen science project.

The inward dust flow also passes by Saturn, where NASA happens to have a spacecraft with a dust collection system. This is Cassini, which was outfitted with that capability with the intention of capturing dust native to Saturn's rings. It just happened to be in the right place with the right tools to catch some interstellar dust.

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