NASA crashed a spacecraft into an asteroid

Perth, Australia:

NASA DART Mission – Double Asteroid Redirect Test – was humanity’s first planetary defense mission in the real world.

In September 2022, the DART spacecraft collided with the companion “moon” of a small asteroid 11 million kilometers from Earth. One of the goals was to find out if we can give these things a push if someone was coming towards us.

By gathering lots of data on approach and after impact, we would also have a better idea of ​​what would happen to us if such an asteroid hit Earth.

Five new studies published in Nature Communications today we use the images sent by DART and its travel companion LICIACube to unravel the origins of the Didymos-Dimorphos double asteroid system. They also contextualized this data for other asteroids out there.

Asteroids are natural hazards

Our Solar System is full of small asteroids – debris that never reached the planets. Those that come close to Earth’s orbit around the Sun are called Near-Earth Objects (NEOs). These pose the greatest risk to us, but they are also the most affordable.

Planetary defense against these natural dangers really depends on knowing their composition – not just what they are made of, but how they are made up. Are they solid objects that will pierce our atmosphere if given the chance, or are they more like piles of rubblebarely kept together?

The asteroid Didymos and its small moon Dimorphos are known as a binary asteroid system. They were the perfect target for the DART mission because the effects of the impact could be easily measured in changes to Dimorphos’ orbit.

They are also close (more or less) to Earth, or at least they are NEOs. And they’re a very common type of asteroid that we haven’t seen well before. The opportunity to also learn how binary asteroids form was the icing on the cake.

Several binary asteroid systems have been discovered, but planetary scientists don’t know exactly how they form. In one of the new studies, a team led by Olivier Barnouin from Johns Hopkins University in the United States, used images from DART and LICIACube to estimate the age of the system by observing surface roughness and crater records.

They found that Didymos is about 12.5 million years old, while its moon Dimorphos formed less than 300,000 years ago. That may still seem like a lot, but it’s much younger than anyone expected.

A pile of stones

Dimorphos is also not a solid rock as we normally imagine. It’s a pile of rocks that barely hold together. Coupled with their young age, it shows that there may be multiple “generations” of these asteroids stacked together after larger asteroid collisions.

Sunlight actually causes small bodies like asteroids rotate. When Didymos began to spin like a top, its shape became flattened and swollen in the middle. This was enough to cause large chunks to roll off the main body, with some even leaving traces.

These pieces slowly created a ring of debris around Didymos. Over time, as the debris began to coalesce, it formed the smaller moon, Dimorphos.

Another study, led by Maurício Pajola from Auburn University in the US used cobblestone distributions to confirm this. The team also found that there were significantly more (up to five times) large rocks than seen on other non-binary asteroids that humans have visited.

Another of the new studies shows us that the rocks on all the asteroids that space missions have visited so far (Itokawa, Ryugu and Bennu) were probably the same shape. But this excess of larger rocks in the Didymos system may be a unique feature of the binaries.

Lastly, another article shows this type of asteroid appears to be more susceptible to cracking. This happens due to heating-cooling cycles between day and night: like a freeze-thaw cycle, but without water.

This means that if something (like a spacecraft) impacted it, there would be a lot more debris thrown into space. It would even increase the amount of “push” it could have. But there’s a good chance that what’s underneath is much stronger than what we see on the surface.

This is where the European Space Agency Your mission Not only will it be able to provide high-resolution images of DART impact sites, but it will also be able to probe the interiors of asteroids using low-frequency radar.

The DART mission not only tested our ability to protect ourselves from future asteroid impacts, but also enlightened us about the formation and evolution of rubble piles and binary asteroids near Earth.

(Author:Eleanor K. SansomAssociate Researcher, Curtin University)

(Disclosure statement:Eleanor K. Sansom receives funding from the International Radio Astronomy Research Center and is supported by the Australian Research Council)

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