On June 8, NASA revealed that its powerful new space observatory, the James Webb Space Telescope, now has a small hole in one of its primary mirrors after being launched by a larger-than-expected micrometeoroid. deep space. The news was a bit shocking, as the impact took place just five months after the length of the telescope’s space, but these blows are simply an inevitable aspect of space travel, and there are certainly more thwacks on the way.
Despite what its name suggests, the space is not exactly empty. Within our Solar System, small pieces of space dust move through the regions between our planets at enormous speeds that can reach tens of thousands of miles per hour. These micrometeoroids, no larger than a grain of sand, are usually small pieces of asteroids or comets that have broken and now orbit the Sun. And they are everywhere. An approximate estimate of small meteoroids in the inner Solar System puts their combined total mass at about 55 trillion tons (if they were all combined into one rock, it would be about the size of a small island).
small pieces of space dust move through the regions between our planets at an enormous speed
This means that if you send a spacecraft into deep space, your hardware is sure to be hit by one of these small pieces of space rock at some point. Knowing this, spacecraft engineers will build their vehicles with certain protections to protect themselves from micrometeoroid shocks. They will often incorporate something called Whipple shielding, a special multi-layered barrier. If the shield is hit by a micrometeoroid, the particle will pass through the first layer and fragment even further, so that the second layer will be hit by even smaller particles. This shield is typically used around sensitive spacecraft components for added protection.
But with NASA’s James Webb Space Telescope, or JWST, it’s more complicated. The gold-plated telescope mirrors must be exposed to the space environment in order to properly collect light from the distant universe. And while these mirrors were built to withstand some impacts, they are more or less sitting ducks for larger micrometeoroid strokes, like the one that hit JWST in May. Although the micrometeoroid was still smaller than a grain of sand, it was larger than NASA predicted, enough to damage one of the mirrors.
Spacecraft operators model the micrometeoroid population in space to better understand how often a spacecraft can be hit anywhere in the Solar System and what size particles could be destroying its hardware. But even then, it is not an infallible system. “Everything is probability,” David Malaspina, an astrophysicist at the University of Colorado who focuses on the impacts of cosmic dust on spacecraft, tells The Virgin. “You can only say, ‘I have this chance of being hit by this particle of size.’
Examples of different types of Whipple shielding Image: NASA
Micrometeoroids have a wide range of histories of origin. They can be the leftover products of high-speed collisions in space, which pulverize space rocks into tiny pieces. Asteroids and comets are also bombarded over time by space particles and photons from the Sun, causing them to break into small pieces. An asteroid can also get too close to a large planet like Jupiter, where the strong gravitational pull pulls out pieces of rock. Or an object can get too close to the Sun and heat up too much, causing the rock to expand and break into pieces. There are even interstellar micrometeoroids that are passing through our Solar System from more distant cosmic neighborhoods.
Micrometeoroids have a wide range of histories of origin
The speed with which these particles move depends on which region of space they are in and the path they take around our star, averaging about 45,000 miles per hour or 20 kilometers per second. Whether or not they will face your spaceship also depends on where your vehicle lives in space and how fast it moves. For example, NASA’s Parker solar probe is the closest man-made object to the Sun at the moment, moving at a maximum speed of over 400,000 miles per hour. “It reaches the 4-yard line, compared to the Earth which is in an extreme zone,” says Malaspina, who has focused on studying the impacts of micrometeoroids on the Parker solar probe. It also moves through the densest part of a region called the zodiacal cloud, a thick disk of space particles that permeates our Solar System. Thus, the Parker Solar Probe is scattering sand more frequently than JWST, and is hitting these particles at incredibly high speeds that the telescope would receive.
The Parker Solar Probe is giving us a better understanding of micrometeoroids around the Sun, but we also have a good understanding of the population around the Earth. Whenever a micrometeoroid hits the upper atmosphere of our planet, it burns and creates meteor smoke: fine particles of smoke that can be measured. The amount of this smoke can tell us how much dust is hitting the Earth over time. In addition, there have been experiments at the International Space Station, where materials have been mounted outside the orbiting laboratory to see how often they are bombed.
An artistic representation of NASA’s Parker solar probe Image: NASA
Although JWST lives approximately 1 million miles from Earth, it is still relatively close. Scientists also have an idea of what is out there based on other missions sent into orbit similar to the JWST. And most things that come to the telescope are not very big. “Spaceships are hit by the little ones all the time,” says Malaspina. “Little by little, I mean micron fractions, much, much, much smaller than human hair. And for the most part, spacecraft don’t even notice.” In fact, JWST was already hit by small micrometeoroids four times before being hit by the larger micrometeoroid in May.
“You just have to live with the probability that you will end up hitting.”
NASA modeled the micrometeoroid environment before the launch of JWST, but in light of the recent impact, the agency has convened a new team to refine its models and better predict what could happen to the telescope after future impacts. Current micrometeoroid modeling will attempt to predict things such as how debris spreads through an orbit if an asteroid or comet breaks. This type of waste is more dynamic, says Malaspina, making it more difficult to predict.
At the end of the day, however, the prediction will simply give you more insight into when a spacecraft could be hit by a large chunk of dust. Occasional impacts like this are simply inevitable. JWST will continue to be received over time, but it was an eventuality for which NASA was always ready. “You just have to be more discriminating with the help you render toward other people.”