Tiny dust-free asteroids orbiting Earth reveal a big secret about solar storms

Small asteroids like Bennu or Ryugu are devoid of dust. For a long time, scientists have wondered why. Now it turns out that our sun and the severe solar storms may have something to do with it.

Asteroids are strange. Some are made of rocks, others are made of ice (Themis), sometimes they twist and sometimes they just tumble (Toutatis) and they can be tens of kilometers wide to several centimeters. And scientists have spent years trying to understand these anomalies in asteroids and the cause behind them, because they might reveal something important to us. And it seems that scientists have come across such a thing. Smaller asteroids like Bennu and Ryugu share a very intriguing feature: they are all dust-free. And scientists have found that this feature is caused by various solar activities, including solar storms.

It may seem a little strange to think that a solar storm can dust off asteroids and to understand its relevance to us, but rest assured, it reveals information that could be useful to us. Scientists discovered this phenomenon very recently after spacecraft Hayabusa2 and OSIRIS-REx visited the two asteroids and saw that their surfaces are not smooth like the large asteroids such as Vesta. The bodies of these smaller asteroids looked like a rocky fissure with tiny rocks dumped all over and no speck of dust to bind them together.

Dust-free asteroids provide important warning against solar storms

A new study, published in the journal Nature, highlights that smaller asteroids lose surface dust as a result of a process known as electrostatic repulsion. In simple terms, electrostatic repulsion means that two particles with the same charge repel each other. And the study has shown that the sun’s ultraviolet radiation causes this in the smaller asteroids. So when these rays hit the dust, the dust loses electrons from its atomic structure, and once they’re charged, they shoot off the asteroid and plunge into empty space.

But why is this phenomenon only visible in smaller asteroids? The answer is simple. Due to their smaller size, the asteroids have a weaker gravity and cannot compensate for the repulsion of similar charges.

And how does it relate to us? Well, solar storms carry similar radiations. And knowing that this is the effect that the sun’s radiation can have on the dust particles, the assumption is that the same could happen to the small instruments in the satellites orbiting the Earth’s upper orbit. While they are not at risk of being thrown into space, being zapped by UV rays can affect their functioning by charging the instruments. Some of these satellites are used for critical communications and security purposes, and the slightest change in the reading of these instruments can be very problematic.

This information will help scientists not only better understand the asteroids, but also devise better ways to protect satellites from solar storms.

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