Asteroids are fragments left over from the formation of our Solar System 4.6 billion years ago, and the vast majority of them orbit the Sun somewhere between Mars and Jupiter.

Asteroid orbits can change over time, and they can come dangerously close to Earth

However, due to the gravitational interaction with Jupiter, the largest planet in the Solar System, the orbits of asteroids can change over time, and they can approach Earth, sometimes dangerously close. Of the more than 1.1 million asteroids identified to date, approximately 30,000 have orbits less than 1.3 astronomical units (AU) from the Sun.

Now, one astronomical unit (1 AU) is the distance between the Earth and the Sun, so these asteroids, which we call Near-Earth Objects (NEAs), can pose a danger to us because their orbits can put them on a path that crosses the Earth . More than 1,400 such asteroids have more than zero chance of hitting Earth in the more or less distant future, but space agencies are keeping an eye on them and promise to let us know if one of them is headed for Earth. The good news is that their orbits are fairly predictable, meaning we’ll have a head start of at least a few years if we’re astronomically unlucky.

If until now we have been content to just observe them, fortunately we have started to take concrete steps to protect ourselves from possible dangerous asteroids: the DART mission was successful because a probe sent from Earth collided with an asteroid (Dimorphos) and it succeeded so well that its orbital period around another asteroid (Didymos) was reduced by a factor of three compared to the originally estimated time interval.

Maybe deflecting an asteroid is easier than we thought. The tail of Didymos is now more than 10,000 km long as a result of the collision with the DART probe

And this means that returning an asteroid is easier than we previously thought. Moreover, the tail of Didymos is now more than 10,000 km long, resulting from the collision with the DART probe. In the future, the European mission called HERA, which also includes institutions from Romania, will revisit the asteroid Dimorphos for further studies of the remnants of the DART impact.

However, with the methods we currently have, we need several such impacts and a head start of several decades to deflect an asteroid heading for Earth. Fortunately, no asteroids identified so far (and we already have a catalog of the largest ones) will cross Earth in the next century, which should give us plenty of time to develop more sophisticated methods of protecting the planet.

Because that is the name of this field, which has the role of protecting our planet from a possible catastrophic impact. We cannot predict the trajectory of asteroids in the distant future with high accuracy, because it is difficult to calculate the influence of Jupiter and other planets in the coming decades and centuries, but we can say that the accuracy we have today is high enough that we can be comfortable during next decades.

I said that most asteroids have orbits that lie between the orbits of Mars and Jupiter, but also because of the complex equations of motion in the gravitational fields of several massive objects, there are also asteroids that share an orbit with other bodies that orbit the Sun. , and they are called Trojan asteroids.

Lucy will be closer to Earth than the International Space Station

How is that possible? Throughout the history of the Solar System, they have accumulated in some regions called Lagrangian points L4 and L5, where the gravitational pull of the Sun and a nearby body offset their gravitational attraction. Because their evolution over the past hundreds of millions of years has been different from that of normal asteroids, last year NASA sent the Lucy probe to visit the Trojan asteroids that accompany Jupiter (also called the Jupiter Trojan asteroids).

Although it has some problems with one of its two solar panels (which refused to fully deploy), NASA has decided that the probe’s mission can continue and, starting in 2025, Lucy will fly past 5 Jupiter asteroids. But until then, Lucy will need to adjust her trajectory on the way to Jupiter’s orbit, and to do so, she will return to Earth and use Earth’s gravity to accelerate to a higher speed.

The flyby is scheduled for tomorrow, Sunday, October 16, when it will be exactly one year since the probe was launched into space (using an Atlas V rocket in the 401 configuration). And the probe will rush past us, approaching 350 km from the Earth’s surface. So for a few minutes,

Lucy will be closer to Earth than the International Space Station. This flyby is not without risk, because at such an altitude there is always a chance that a satellite or piece of space debris could enter the probe. The second flyby will take place next year, before the first Jupiter asteroid flybys.

So can we protect ourselves from asteroids? Not really yet, but we’ve started looking into how to do it in the future. Fortunately, we probably won’t have to for the next hundred years. We’re using this time to learn more about asteroids to discover as many of them as possible, but we’re also preparing to have the right methods for disposing of them if we ever find one on our way through space.

Photo author: Dreamtime