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[Music throughout] The solar system is full of rocks,

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but not all of them are large.

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Dust-size particles shed from comets

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and asteroids, and smaller than a single grain of sand, traverse the 

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solar system at speeds reaching 40,000 miles an hour.

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Our best knowledge of these tiniest meteoroids comes from measurements made near Earth.

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But a clever use of data from the LISA Pathfinder mission has

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tallied these particles nearly a million miles away.

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Launched in 2015 and retired in 2017, LISA

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Pathfinder is an ESA-led mission that demonstrated the technology needed

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to built a future space-based gravitational wave observatory – a tool

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for detecting ripples in space-time produced by, among other

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things, merging black holes. 

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LISA Pathfinder was a resounding success, demonstrating it could keep its

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instruments steadier than any mission previously flown.

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It reduced unwanted forces on its instruments to less than a millionth of a billionth

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of the gravity felt on Earth. To do this,

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LISA Pathfinder had to isolate its instruments from environmental disturbances,

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including occasional micrometeoroid impacts.

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Each strike moved the spacecraft slightly, and it reacted immediately

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by firing small thrusters. The science team found

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and characterized 54 impacts over the mission’s duration, shown

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here as yellow dots. LISA Pathfinder

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did its work while orbiting Earth-Sun L1, a gravitational

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balance point about a million miles toward the Sun. This is

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essentially unexplored territory for understanding the solar system’s dust distribution.

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The science team was able to use data in between

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various other tests to search for dust impacts on the spacecraft,

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seen here as purple regions.

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The findings were broadly consistent with existing ideas of what generates

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micrometeoroids found near Earth. These models predominantly favor nearby

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Jupiter-family comets – like 9P/Tempel 1, 

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103P/Hartley, and 67P/Churyumov-Gerasimenko –

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as the main dust makers, with additional contributions

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from comets with longer periods, like Halley’s Comet.

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Improving our dust knowledge will help future missions assess

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potential hazards for spacecraft operating in the inner solar system.

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It will also help us better understand the dust environments around other stars,

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which can complicate searching for planets around them. And the same

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technique can be used on other precision-measurement missions.

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We’ll learn a bit more about the solar system each time one of these spacecraft is 

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struck by a microscopic crumb.

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[Additional animations courtesy of ESA, Max Planck Institute for Gravitational Physics and Milde Marketing]

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[Explore: solar system & beyond]

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[NASA]