There are a staggering number of asteroids floating around our solar system — and humanity has already counted them. At least 1.4 million peopleThere’s probably a lot more you haven’t seen yet.
Most of the asteroids we have observed orbit our solar system. Main asteroid belt Between Mars and Jupiter, there are also several objects called Near-Earth Objects (NEOs) whose orbits cross those of Earth. Some of these NEOs may collide with Earth, causing effects ranging from beautiful meteor showers to the extinction of entire species.Sorry, dinosaurs).
There are a lot of asteroids in space, and the universe is incredibly vast, so how often do these asteroids actually come close to Earth?
The short answer is that it depends on the size of the asteroid. Just as small earthquakes occur more frequently than large ones, small asteroids pass by Earth more often than catastrophically large rocks.
According to an asteroid expert and MIT professor, Richard BinzelEarth encounters over 10 tons of dust every day, the equivalent of 20 grizzly bears’ worth of dust falling on Earth every day. But these tiny dust particles don’t pose any harm to humans; they simply burn up in Earth’s atmosphere and create wish-fulfilling meteor showers. (If you want to catch a glimpse of one of these, the returning Perseid meteor shower is your chance!)
On the larger side, rocks the size of marbles to bowling balls “fly up several times a day, creating the bright streaks we call fireballs,” Binzel explains. “At the size of a few beach balls, they can fly up several times a year, occasionally producing recoverable fragments that we call meteorites.”
An object the size of a large truck hits the Earth about two or three times per century, and fortunately for humanity, most of these impacts happen over the ocean. About 71% of the Earth’s surface is covered by waterOne of these entered Earth’s atmosphere very recently. Over Chelyabinsk, Russia, 2013It exploded several miles above the Earth’s surface, but the impact was strong enough to shatter windows. An asteroid twice the size of the Chelyabinsk meteorite exploded in another part of Russia in 1908. Tunguska incidentIt flattened entire forests.
The largest asteroids — those larger than 490 feet (140 meters) in diameter, the size of the Washington Monument — are the rarest. “Asteroid impacts in this size range are powerful enough to cause significant local and regional damage, including tsunami hazards if they strike the ocean,” Binzel says. “Fortunately, these impacts are very rare on human timescales, averaging about once every 25,000 years. That’s less than 1% chance per century, but not zero in a human lifetime.” Binzel says about 40% of asteroids in this size range have already been discovered and tracked.
By comparison, the asteroid that wiped out the dinosaurs Thousands Diameter metersThis is an extremely rare event, and we know that a fairly large asteroid (just over 300 meters in diameter) will approach Earth in the near future. ApophisBased on observations, astronomers predict it will come very close to Earth in 2029, 2036, and 2068. Thankfully, the risk of it actually hitting Earth is fairly low.
Astronomers are also working hard to prepare for potentially threatening asteroids. NASA Double Asteroid Reorientation Test (DART) The mission will collide with the asteroid Dimorphos in 2022 to demonstrate the technology needed to deflect the asteroid from a collision course.
One of the big problems in so-called “planetary protection” is identifying the threats in the first place. Just a few weeks ago, two large asteroids (2024 MK and 2011 UL21Asteroids 2024 MK, measuring 150 meters and 2,300 meters in diameter, passed very close to Earth. However, this asteroid was only discovered a week before it passed between the Earth and the Moon, which is a bit worrying.
Finding all the tiny bits of rock bouncing around in our solar system is a daunting task. “Earth and the telescopes we have on it are platforms that are constantly moving in orbit around the Sun. Asteroids are also orbiting, and to find them, they need to be orbiting on the night side of Earth in the direction our telescopes are pointing,” Binzel explains. “The timing of the two orbits can sometimes be out of sync for decades.”
Finding as many asteroids as possible requires large telescopes and cameras that can survey large swaths of the sky multiple times each night. Several facilities currently under construction will take on this task. Vera Rubin Observatory Earth and NEO Surveyor Space satellite. Rubin is a large astronomical observatory currently under construction in Chile. Millions more asteroids discovered it is Scans the entire sky every three nightsNEO Surveyor is a NASA space telescope scheduled to launch in 2027 and is specifically designed to search for asteroids full-time for five years. Hoping to identify more than 90% of potentially hazardous asteroids.
“It would be worrying if we weren’t taking the asteroid challenge seriously,” Binzel adds. “But finally, NASA and its funders are starting to take their adult responsibility to do the research necessary to make sure the future of asteroids is safe.” If all goes well, astronomers will be able to say with confidence whether we can expect a major impact in the next century. And if they find anything dangerous, it might be time to invest in a successor to DART.
