A newly discovered space rock is poised to fly by Earth in approximately 23 years — and while the chance that it hits Earth is not tremendous, among all known asteroids it has the highest chance of hitting Earth, according to NASA.
The asteroid, known as 2023 DW, was only discovered in late February, but it has already skyrocketed to the top spot on the "Risk List," a registry organized by the European Space Agency (ESA) as a way of ranking near-Earth objects with a "non-zero impact probability."
If it were to hit Earth, 2023 DW is big enough that it could rival the Tunguska event, a massive explosion in Siberia in 1908 that flattened 80 million trees.
Originally discovered on February 26 by French astronomers Georges Attard and Alain Maury, 2023 DW zips around the sun every 271 days. It may resemble a lumpy potato, but the asteroid's diameter has been calculated to be around 50 meters (165 feet), about the size of the Arc de Triomphe in Paris. And it's moving fast (relative to Earth), clipping through space at about 15.3 miles (24.6 kilometers) per second.
NASA initially reported there was a 1 in 560 chance that 2023 DW could impact Earth on Valentine's Day, 2046. Later, that number was updated to a 1 in 1,584 chance. That might not sound like much, but it still incredibly high odds compared to the 1,450 other objects on the ESA's Risk List. (Update Friday, March 17: With updated figures, the odds have dropped to 1 in 5847, making it 5th on the list. That's still pretty high, but that threat is expected to drop to almost zero over the coming days.)
"Often when new objects are first discovered, it takes several weeks of data to reduce the uncertainties and adequately predict their orbits years into the future," NASA said on Twitter.
If it were to hit Earth, 2023 DW is big enough that it could rival the Tunguska event, a massive explosion in Siberia in 1908 that flattened 80 million trees, killed at least three people and is the largest impact event on Earth in recorded history. While we are not entirely certain what caused the explosion in the sky, the chief culprit is considered a meteor air burst triggered by an asteroid similar in size to 2023 DW. In contrast, the Chelyabinsk meteor — which exploded over Russia on February 15, 2013 and damaged over 7,200 buildings and hospitalized 112 people — was less than half that size. We could expect a similar fallout if 2023 DW were to slam into Earth, though it really depends on a lot of factors.
Far more devastating impacts have left their mark through Earth's history — and, often, radically changing the evolution of life. The rock that many paleontologists theorize killed the non-avian dinosaurs 66 million years ago was about six miles wide and triggered "mega-earthquakes" that lasted for months, as well as wiping out an estimated 75 percent of all life on Earth. There's no reason to believe such an event couldn't someday repeat itself, so it's prudent to be prepared.
Luckily, NASA and other space agencies have been working on technology to deflect such a deadly impactor. Despite what certain blockbuster films might lead one to believe, it is not smart to use bombs to stop an asteroid. That would just make the problem worse by creating tons of smaller asteroids. Instead, astrophysicists believe the best defense is to knock asteroids off course long before they make their final approach, like a spaceborne billiards game yet with higher stakes.
Last September, NASA and the Johns Hopkins Applied Physics Laboratory deliberately crashed a space probe into an asteroid called Dimorphos as part of the Double Asteroid Redirection Test (DART). The test was a smashing success. Images and video of the impact depicted spectacular trails of debris and it later became clear that the probe altered the orbit of the asteroid as planned. DART has been described in a NASA video as "a watershed moment for planetary defense and humanity."
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On March 1st, a series of articles published in the journal Nature described how this stunt was pulled, how the impact transferred momentum and what kind of stuff was sprayed into space when DART collided with the space rock, which apparently blasted out at least one million kilograms (2.2 million pounds) of rock, creating a tail of rubble stretching for tens of thousands of kilometers. Most importantly, it altered Dimorphos' orbit by about 33 minutes. DART was an extremely successful mission.
This tech is critical for the future of humanity. When it comes to a giant rock hitting our planet, most experts agree that it's not a matter of if, but when. Last December, scientists announced the discovery of three asteroids that were hiding in the glint of the sun, one of them being the largest potentially hazardous near-earth asteroid spotted in eight years. This follows a similar discovery of a "planet killer" asteroid in November, though none of these rocks are considered likely to hit us compared to 2023 DW.
It's not always easy to detect space rocks that could pose a threat to life on Earth, but on a long enough timescale, we are almost guaranteed to be hit by one. We need to be prepared. Whether the technology developed with DART will be deployed against 2023 DW or another menacing space rock remains to be seen, but given that the stakes could literally equal widespread extinction, we can't be too careful.