..,and we didn't see it coming until 95 minutes before.
by Alex Martin
February 8, 2024 @ 1:00pm EST
Searching for Asteroids
More than 100 tons of rock and material fall to Earth from outer space every single day, mostly in the form of small particles that burn up on entry into our atmosphere. Our planet has been hit by its fair share of larger objects as well, comets, asteroids, and in the distant past, at least one protoplanet.
For as long as human civilization has spread around the globe, we've been able to enjoy a relatively stable existence free from chaos raining down from the heavens. But every now and then, Earth does get hit by a bigger object, and with people around to discover or witness the impacts, we have been forced to ask: how do we protect ourselves against asteroids, many of which are traveling tens-of-thousands of miles per hour?
The answer is Planetary Protection. Governments around Earth have set up agencies and programs designed to find asteroids, track their orbits, and predict how close they might come to Earth. We designate these asteroids as NEOs, that is, Near Earth Objects. Despite the term, "near" doesn't necessarily mean these asteroids are grazing Earth. These are objects typically stay millions of miles away, but cross our orbit from time to time.
Blinded by the Sun
When an asteroid is outside of Earth's orbit, it is easy to see from an astronomical standpoint. Sunlight reflects off its surface, and all we have to do is take pictures, compare them to each other, and look for moving dots against the background of stars. Factors such as the change in angle day-to-day help to tell us the distance to the object and its path around the Sun, and factors such as the albedo (reflectivity) help to tell us its size and composition.
It's a different story, however, when an asteroid is coming at us from inside of Earth's orbit.
For the same reason that we don't see stars in many photographs taken while astronauts were on the Moon; for the same reason we don't see other stars during the daytime; and for the same reason it's difficult to see at night when other cars are driving toward you with headlights on, it is extremely difficult, and sometimes downright impossible, to see asteroids heading toward us from the direction of the Sun. The Sun is extremely bright, so its light washes out any other objects near it.
When an asteroid is coming toward Earth from the Sun-side, our telescopes - even those in space - are rendered blind. Darkening the light with filters doesn't help; just as you tone down the sunlight, you're erasing your ability to catch anything else in view.
This task is so difficult that since 2008, we have only found 8 asteroids coming from the Sun-side before they entered Earth's atmosphere. Here's the list:
We've been able to find asteroids that haven't entered our atmosphere before. You'll see snippets on social media or the news about how "an asteroid the size of _______ will pass Earth today." A notable example was on February 15, 2013: we were tracking an asteroid that harmlessly flew past Earth - and it did.
But we didn't see the other one.
Russia, February 2013
In Chelyabinsk, Russia, an asteroid exploded 25 miles above the ground, more than three-times higher than passenger airplanes fly. Traffic cameras, cell phones, dashcams, and more all recorded the event: a streak of white smoke in the sky, followed by an intense flash, then nothing. And for nearly two minutes...nothing happened. Video
Until the shockwave reached the ground, blasting windows out of buildings, setting off car alarms, knocking people off their feet.
No casualties were reported, but around 1,300 people were injured that morning. The silence that followed the flash of light was the calm before the storm. The injuries were mostly attributed to people thinking that because nothing had immediately come of the explosion, that it was safe to go look outside again. So when the shockwave hit, people were vulnerable again.
So what happened above Berlin in January 2024?
Just before midnight on January 20th, Krisztián Sárneczky, a self-proclaimed asteroid hunter, detected Asteroid 2024 BX1 using a 60cm telescope at an observatory in Hungary. He went onto social media and reported the finding, saying he'd calculated that the 1-meter diameter asteroid would disintegrate above West Berlin around 1:30am local time.
Astronomers and late-night enthusiasts immediately took action and began scanning the skies of Berlin. Then, at 1:32am CET, a fireball cruised through the atmosphere, proving the prediction accurate. Videos of the event were streamed live and social media lit up with the news of the cosmic visitor. Video
We have no choice: we MUST find asteroids
The detection of the Berlin asteroid, though successful, puts into perspective the importance of developing Planetary Protection programs around the globe. Asteroids exploding above the Earth can make for cool light shows if they aren't so big they produce a destructive shockwave. But it's important that we find, track, and manage NEOs, and in some cases, develop technologies to defend against them. As a civilization, Planetary Protection means safeguarding ourselves from mass casualty events, or even extinction. A 100-meter wide asteroid impacting the ground can destroy a city. There's a crater in the middle of the Arizona desert that serves as a reminder of that reality. A 1000-meter wide asteroid, on the other hand, can destroy thousands of square miles.
We don't live in the chaotic birth of the solar system, where asteroid and meteorite impacts would have been hourly. But we do live in a time where the wrong asteroid (or solar flare!) taking out a series of satellites, or destroying a city, would have consequences for the entire world on technological and political scales. We're working on developing these defenses: the DART mission (Double-Asteroid Redirection Test) that smashed a satellite into a harmless asteroid measured that "Kinetic Impactor Asteroid Defense" - a.k.a "ram a rocket into it as hard as we can" - is capable of slightly altering the orbit. The technique wouldn't work if the asteroid is hours or days away from hitting Earth, but months or years out, and that slight push can be enough to nudge the asteroid just off-course and avoid an impact.
As far as we know, there are no extinction-level asteroids on a near-future trajectory with the Earth. But that's why it's so important to look now, so we have time to prepare and develop the technology we need. Asteroid impacts may be unlikely for any one person to experience, but over long periods of time, they are inevitable, and whether on Earth, Mars, the Moon, or elsewhere, humanity will eventually face up against one that poses a dire threat.
As astronomers like to joke, "If the dinosaurs had a space program, they might still be here."
But if they had...then maybe we wouldn't be here.
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