NASA recently announced that the James Webb telescope was hit by a larger-than-normal micrometeorite. This caused damage to one of the telescope’s eighteen mirrors. Space dust can cause major problems for spacecraft, which is why the organization already takes this into account in the design.
It is often thought that the space is empty, but that is not the case. The space between different planets and stars is filled with, among other things, enormous amounts of thinly spread gas and dust.
The dust particles can come from different sources, for example from asteroids. These micrometeorites orbit the sun and can reach speeds of tens of thousands of kilometers per hour. They are often smaller than a grain of sand and weigh less than a gram.
The James Webb telescope has been hit by at least four different micrometeorites since its launch in December. NASA emphasized that coming into contact with micrometeorites is inevitable for a telescope of this size.
Shield of different layers
The space agency already takes this into account when designing spacecraft. Usually the vessels are equipped with some form of protection to stop micrometeorites. This is called the Whipple shield.
The shield consists of a barrier of several layers. If hit by a micrometeorite, the particle will pass through the first layer before fragmenting further. The second layer is then hit by even smaller particles. The shield is usually used around sensitive parts of spacecraft for extra protection.
However, applying such a layer to the mirrors of the James Webb telescope is impossible, because they will then no longer be able to collect the light. However, the mirrors are built in such a way that they can withstand shocks up to a certain height. However, the micrometeorite was larger than NASA had anticipated, causing damage to one of the mirrors.
Making a correct calculation is difficult
In any case, the space agency regularly calculates how often a vessel will be hit by fragments and at what speed this will occur. However, that is not a foolproof system, a space expert tells The Verge†
How fast the dust particles move depends on which part of the room they are in and which path they follow. Whether they might come into contact with a spacecraft depends on where it is at the time and what speed it is at.
Ultimately, it is inevitable that a spacecraft will be hit by a dust particle. All NASA can do is develop a craft that can withstand this to a certain extent.
The James Webb has managed to do just that so far: the impact had no direct consequences for the functioning of the telescope. However, the mirror must be readjusted because of the distortion. It is unclear whether this has already happened.