The existence of this asteroid dates back 4 billion years. That Might Be a Serious Issue

 By FRED JOURDAN & NICK TIMMS, THE CONVERSATION

January 24, 2023

As asteroids and comets, enormous quantities of rocks and other material are flying across our Solar System. Could we effectively avert an asteroid collision with Earth if one of these headed our way?

Okay, perhaps. But it seems that there is one kind of asteroid that may be particularly challenging to destroy.

Asteroids are pieces of rocky debris in outer space that are left over from our Solar System's more violent history. They may be studied to learn more about their physical characteristics, hints about the Solar System's distant past, and the dangers these space rocks represent to Earth.

There are two primary asteroid kinds.

Asteroids may be divided into two primary categories and are mostly found in the asteroid belt.

When people think about asteroids, they typically picture monoliths, which are solid rock formations.

One kilometer-diameter monolithic asteroids are expected to last just a few hundred million years in the asteroid belt, according to predictions. Given the age of our Solar System, this is by no means a lengthy time.

The other kind of asteroids are debris fields. These are formed totally of many fragments that were expelled following the total or partial disintegration of pre-existing monolithic asteroids.

Rubble pile asteroids may have a long life, but we don't really know how durable they are.

sly and many debris fields

NASA's DART mission (Double Asteroid Redirection Test) successfully collided with the asteroid Dimorphos in September 2022. This mission's objective was to see if we could impact an asteroid with a small spacecraft and deflect it. It was a resounding success.

Dimorphos is another another asteroid that has been reduced to a mass of debris, just like previous recent asteroid expeditions by the Japan Aerospace Exploration Agency (JAXA) to visit asteroids Itokawa and Ryugu and by NASA to asteroid Bennu.

These missions demonstrated to us that since rubble pile asteroids are porous, they have a low density. They are also plentiful. In truth, they are numerous, and because they are fragments of monolithic asteroids, they are tiny and difficult to see from Earth.

Because of this, these asteroids pose a serious threat to Earth, and we thus need to learn more about them.

Studying asteroid dust

The JAXA-built Hayabusa spacecraft made its way back from the 535-meter-long, peanut-shaped asteroid Itokawa in 2010. More than a thousand rock fragments, each hardly larger than a sand grain, were carried by the probe. Those were the first asteroid samples ever returned!

The images captured by the Hayabusa spacecraft while it was still circling Itokawa turned out to be the first to show the presence of debris pile asteroids.

According to preliminary findings by the JAXA team that examined the materials that were returned, Itokawa originated following the total annihilation of a parent asteroid that was at least 20 kilometres in size.

In our recent study, we used two methods to analyse a number of dust particles brought back by the asteroid Itokawa. The first method involved shooting an electron beam at the particle and looking for electrons that scattered back. It reveals if a rock has been shaken by a meteor strike.

The second method, known as argon-argon dating, makes use of a laser beam to gauge the amount of radioactive decay that has taken place within a crystal. It tells us how old the meteor impact was.

giant, indestructible space pillows

Our findings demonstrated that the enormous collision that created Itokawa and killed its parent asteroid occurred more than 4.2 billion years ago, or almost as ancient as the Solar System itself.

That outcome was wholly unanticipated. It also implies that Itokawa has endured for a lot longer than its behemoth competitors.

Its shock-absorbent properties are responsible for an asteroid's astoundingly lengthy life span. Itokawa, being a mound of debris, is around 40% permeable.

In other words, because over half of it is made up of voids, repeated impacts will just compress the spaces between the rocks rather than fracturing them.

Itokawa is therefore comparable to a huge space cushion.

This finding suggests that debris pile asteroids are significantly more common than previously believed in the asteroid belt. They seem to be quite difficult to eradicate once they have formed.

To avoid an asteroid hitting Earth, it is essential to have this knowledge. Even if the DART mission was effective in shifting the asteroid it was aiming for, there is very little kinetic energy that can be transferred between a tiny spacecraft and an asteroid that is littered with debris. This indicates that they are inherently resistant to crumbling under pressure.

We would thus prefer a more proactive strategy if an oncoming asteroid posed an immediate and unexpected threat to Earth.

For instance, we might need to employ the shockwave from a nuclear explosion in orbit since powerful explosions can push an asteroid away by transferring a lot more kinetic energy to its naturally cushioned debris field.

Then, should we put a nuclear shock wave strategy to the test? That is a completely unrelated query.

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