Micrometeoroids

Micrometeoroids are small solid particles that travel through space. In planetary science, they are usually defined as meteoroids roughly 10 micrometers to 1 millimeter in size, forming part of the broader population known as interplanetary dust. They originate from collisions between asteroids, from cometary debris, and from the erosion of space rocks as they travel through the solar system.

These particles move at very high speeds when they encounter a planet or spacecraft, typically tens of kilometers per second relative to the object. Most burn up in the atmosphere, producing meteors, but a fraction survive as micrometeoroids that reach the surface, particularly in clean environments such as Antarctic ice or deep-sea sediments. The majority of micrometeoroids that strike a spacecraft are ablated or deflected by shielding and do not reach the surface.

Because direct in situ sampling in space is challenging, scientists study micrometeoroids by collecting fallen micrometeorites on Earth and by retrieving dust captured by spacecraft instrumentation and aerogel collectors, such as in certain missions. Analyses reveal a mix of silicate minerals, metals, and glassy phases, with compositions reflecting diverse solar-system sources.

From an engineering perspective, micrometeoroids pose a risk to spacecraft during high-velocity impacts, potentially eroding surfaces or penetrating shielding. Spacecraft design often incorporates protective measures to mitigate damage from such strikes.

Micrometeoroids are a key component of cosmic dust, providing information about the early solar system and ongoing processes that shape planetary environments.