A near miss, sort of by Angela Rieck

Okay, I am being overly dramatic by the title, the asteroid YR4 was initially projected to have a 3.1% chance of hitting the earth in 2032. A day later, NASA downgraded it significantly and by February 21st, the space agency lowered its chances of a potential strike to 0.28%. At the same time, they increased the asteroid’s chances to 1% of hitting the moon. 

First, it’s a relief. This asteroid whose full name is 2024YR4 has a width of 177 feet (54 meters) and is considered a “city killer.” While its impact would not be as devastating as the asteroid that wiped out the dinosaurs (it had a width of 10-15 kilometers), YR4 would be large enough to eviscerate a major city. It would release more than 500 times the energy released by the Hiroshima atomic bomb. If the asteroid landed in the ocean, it could spare a city but create an immense tsunami.

At its peak, YR4 was the highest impact-probability NASA had ever recorded for a space object as large as YR4. The latest reduction in impact probability came after astronomers made overnight observations of YR4 in mid-February. The darker skies enabled astronomers to get a better observation of the asteroid. Even while YR4’s impact odds were going up, the increase was due to uncertainty about the asteroid’s orbital path. 

But there are misses. In 2023, an asteroid, 2023NT1, came close to earth and astronomers did not see it due to the sun’s glare. Astronomers didn’t catch the skyscraper-size rock until two days after it passed, when it was discovered leaving earth’s path by a telescope in South Africa. 

There are a couple of other asteroids that we need to be aware of. In 2029, another city-killer, asteroid Apopohis, will pass earth even closer than some of our satellites, but for now, it has zero chance of crashing into the earth. 

Astronomers are also closely watching the asteroid Bennu (.5 kilometers). This asteroid was the target of the 2023 OSIRIS-REx mission, which proved that a spacecraft could retrieve samples of space rock and return them to Earth. There is currently a 1-in-2,700 chance that Bennu will crash into Earth in 2082, pretty low odds.

There is a system for reporting asteroids and keeping track of them. Scientists and amateur astronomers search the skies each night for tiny dots of moving light. Most of these observations are generally made with ground-based telescopes like the Catalina Sky Survey in Arizona or the Infrared Telescope Facility atop Hawaii’s Mauna Kea volcano. The Asteroid Terrestrial-impact Last Alert System (ATLAS) is an array of telescopes designed to spot asteroids several days to weeks before any potential impact. 

When someone observes an asteroid or a comet, they report it to the International Astronomical Union (IAU) Minor Planet Center, which compiles all of the observations. From there, scientists at other observatories and NASA can make more measurements to determine the object’s precise orbit and whether it may threaten Earth. The International Astronomical Union (IAU) is a non-governmental organization that is responsible for, among other things, naming celestial objects and defining types of objects like planets and dwarf planets. (They are the ones that determined that Pluto was a dwarf planet.)

So, what happens if there is an asteroid heading for earth? Is there something that we can do? 

NASA scientists believe that the best method to address this threat is to alter the asteroid’s orbital path. They have studied several ways or doing this. One method is called a gravity tractor, in which a spacecraft would orbit an asteroid and tug it off course. The most feasible strategy involves launching a spacecraft that would deliberately collide with the asteroid to knock it off course. In 2022, NASA provided a proof of concept by altering the course of the space rock Dimorphos by 32 minutes. Unfortunately, this method requires years of careful planning and a precise knowledge of the asteroid’s orbit.

While all of this seems daunting, scientists currently believe that the earth will be safe from extinction-inducing asteroids for the next thousand years. Let’s hope that the earth is safe from us by that time, too.

Angela Rieck, a Caroline County native, received her PhD in Mathematical Psychology from the University of Maryland and worked as a scientist at Bell Labs, and other high-tech companies in New Jersey before retiring as a corporate executive. Angela and her dogs divide their time between St Michaels and Key West Florida. Her daughter lives and works in New York City.