On June 8, NASA revealed that its new powerful spacecraft, the James Webb Space Telescope, is now playing a small dimple on one of its primary mirrors after being dropped by a larger micrometeoroid than expected in deep space. The news came as a shock as the impact took place just five months into the telescope era – but such strikes are simply an inevitable part of space travel, and more thwacks are on the way.
Despite its meaning, space is empty. Inside our Solar System, tiny particles of space dust are moving across the center of our planets at speeds of up to tens of thousands of miles per hour. These micrometeoroids, which are no more than a grain of sand, are usually small fragments of asteroids or broken comets and orbit around the Sun. And they are everywhere. The heavy scale of small meteoroids in the internal Solar System puts their combined weight at about 55 trillion tons (if they were all wrapped up in one rock, it would be the size of a small island).
That means that if you send a spacecraft into deep space, your hardware will hit one of these pieces of space rock at some point. Knowing this, spacecraft engineers will build their vehicles with special protection to protect them from micrometeoroid strikes. They usually include Whipple shielding, a particular barrier for many layers. When a micrometeoroid hits the shield, the particle will pass through the first layer, and even more so, the second layer is hit by smaller particles. Such protections are often used in critical areas of the spacecraft for extra protection.
But with, NASA’s James Webb Space Telescope, or JWST, is complex. Gold-plated telescope mirrors should be reflected in the atmosphere to collect light from a distant surface properly. And although these mirrors are designed to withstand other impacts, they are ducks that sit on significant micrometeoroid strikes, such as the one that struck the JWST in May. Although the micrometeoroid was smaller than a grain of sand, it was larger than NASA expected – it was enough to cause damage to one of the mirrors.
Space operators model the number of micrometeoroids in space to better understand how many times a spacecraft can be hit on any particular part of the Solar System – and what particles might interfere with their hardware. But still, it is not a senseless plan. “Everything is possible,” David Malaspina, an astronomer at the University of Colorado who focuses on the effects of cosmic dust on spacecraft, tells The Verge. “Do not just say, ‘I have a chance to hit this particle.’ But whether you do it or not, it will happen by accident.”