Editor’s note: Don Lincoln is a senior scientist at Fermi National Accelerator Laboratory. He is the author of several science books for a general audience, including the bestselling audiobook The Theory of Everything: The Quest to Explain All Truth. It also produces a series of science education videos. Follow him on Facebook. The opinions expressed in this comment are solely his own. View more opinion on CNN.
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Once about 66 million years ago, a massive boulder 6 to 10 miles wide across the skies of what is today Central America plunged into the waters of the Yucatan Peninsula, near Chicxulub, Mexico.
The impact caused huge tsunamis that swept the sea and land over hundreds of miles and threw water and debris into the atmosphere. The resulting clouds caused global cooling around the world, killing 75% of plant and animal species alive at the time, including the most famous non-avian dinosaurs, thus reshaping the planet’s biosphere in ways that led to the Cenozoic Era – Also known as the age of mammals – and making human possible.
Given such massive destruction and dire consequences, we can’t help but ask the question: “Could this happen again?”
The answer is yes.
But things are different now. Humans invented a technology that might be able to avert a similar future catastrophe. On Monday, researchers will see if it works, in a crucial test of a potential future planetary defense system that NASA is developing.
A group of scientists and engineers led by the Johns Hopkins University Applied Physics Laboratory will blast a 570-kilogram spacecraft called the Double Asteroid Redirection Test (DART) at an asteroid called Demorphos. The test will determine whether the impact will alter the asteroid’s path and help scientists understand whether potentially dangerous space rocks can be diverted before endangering Earth.
Dimorphos itself does not pose such a threat. It is a small asteroid orbiting a much larger planet called Didymus. Both are not on the path to hitting the ground. However, together, they are an ideal laboratory to test whether hitting a spacecraft on an asteroid could change that asteroid’s path.
The two asteroids form a so-called ecliptic binary, which means that, as seen from Earth, Demorphos passes in front of the larger asteroid as it orbits. This allows ground-based telescopes to very accurately measure their orbital time, which is currently only 12 hours.
Immediately after the impact of DART on Dimorphos, its orbital time is expected to change by several minutes. If successful, space agencies on Earth can begin to develop a program that can be used in the future, the most threatening space rocks.
It is worth asking whether an asteroid collision with Earth poses a real danger; Perhaps cosmic influences are very rare and can be ignored as a risk. After all, it was the impact that killed the non-avian dinosaurs about 66 million years ago — and humans only existed as a species for a few hundred thousand years. There are some advantages in this position. Effects like those of Chixculub are indeed rare.
But that’s because the asteroid was so big. Smaller objects collide with Earth all the time, from pebbles and grains of sand that make meteors to even larger ones, with real consequences. More than 50,000 years ago, a rock 150 feet wide and weighing several hundred thousand tons in the Arizona desert smashed into a force 150 times greater than the bomb that destroyed Hiroshima and left a nearly mile-long crater that is still visible today.
In 1908, a meteorite hit the Earth’s atmosphere near Tunguska, Siberia. The energy from the event was the equivalent of 10 to 15 megatons of TNT. Although the meteor did not reach Earth, it created a devastating shock wave that flattened trees over an area of 830 square miles, shattering glass and driving people off their feet hundreds of miles away.
Recently, in 2013, another large meteor hit the Earth’s atmosphere over Chelyabinsk, Russia. This event, which also resulted in a shock wave rather than an impact crater, was caused by a rock about 56 feet in diameter. The Chelyabinsk meteorite released an energy equivalent to 470,000 tons of TNT, or about 30-40 times the energy of the Hiroshima bomb. About 1,200 people were injured due to the collision.
So, the risk of a catastrophic impact of an asteroid or meteor is real. The Chelyabinsk accident involved a relatively small asteroid, and people are still hit by it. Had the Tunguska or Arizona event occurred over a densely populated area, the damage would have been much greater. Had the Arizona impact occurred in the ocean near the coast, it might have caused a tsunami that would have swept across the land, destroying everything in its path. Significant impact on the east coast of the United States can cause waves up to the foothills of the Appalachian Mountains.
So, the DART effort is not a substitute. It is a deliberate and proactive attempt to guard against a very real danger.
However, being able to divert asteroids is only part of the effort. We also need to know where they are – the sooner the better. If an asteroid is about to hit the Earth, it will be very difficult to deflect it; If we had years of warning, the asteroid could deflect with a much smaller force.
To achieve this early warning, NASA created the Center for Near-Earth Objects, or Near-Earth Objects, to identify space rocks that could endanger Earth. To date, nearly 30,000 objects have been discovered, of which about 10,000 are larger than 140 meters (just under 500 feet) and over 850 more than a kilometer (just over half a mile) in diameter.
None of the rocks discovered poses an immediate threat. On the other hand, not everything is found. The NEO Center estimates that about two-thirds of NEOs larger than 140 meters have been detected, so there’s more to be found.
For those of us who love the big screen, this quiz turns movie stuff into reality. The Hollywood films “Deep Impact” and “Armageddon” depicted the exact problem that the Planetary Coordination Office was designed to avoid. And let’s not forget the latest Netflix movie “Don’t Look Up.” While the movie is a broader cinematic statement about the dangers of ignoring many known global dangers, the threat of a massive meteorite, used as a metaphor in the movie, is a plausible scenario.
In fact, Earth is in a cosmic fire fair, and large boulders from space have hit the planet for millions of years. We need to find these dangers and learn to protect ourselves from them. After all, it’s not about whether the Earth will ever hit again. It’s a matter of time.