The asteroid 2024 YR4 is named after the year it was discovered. Its orbit around the Sun briefly intersects with the path of Earth in eight years. The space rock, named 2024 YR4, has a very low chance of hitting land , either on Earth, or even less likely the moon. Astronomers have set the likelihood of a collision at around 2%.
NASA and other international space agencies take any threat, no matter how small, seriously. Richard Moissl is the head of European Space Agency’s planetary defence office. He said that their attention shouldn’t raise public concerns. In the conversation below, which was edited to make it clearer, he shared some key facts with CBS News about the asteroid.
When will the asteroid strike Earth?
Every four years, this asteroid passes by us. It has completed one full turn every time we complete four trips around the sun. The flyby was just completed in December of 2024. This means that the next flyby will be in December of 2028. We know this one won’t cause any problems.
The most critical is 2032 on the 22nd December, around midday in Universal Time. The asteroid will pass through the Earth’s orbit at that time. It’s actually going through Earth’s path, in a sense.
The question is whether Earth will still be there or if it has already passed that point or is still on its way. The question is, where will Earth pass? There is a region of uncertainty that covers the Earth-Moon System. This does not mean that we do not know much about it. We know a great deal about it.
We’re now looking at the closing moments of time in 2032. The question is fractions of a second per meter, which can make all the differences.
The Earth has a window of about 20 minutes before the asteroid can no longer be in its path or it cannot contact the Earth.
How does the risk of asteroids get managed?
We used to measure the sky every day with different telescopes. We had to take a break for a few days due to the full-moon, the object being close enough to the full-moon, and because the moon was illuminating too much of the sky to be able to see the object.
We will no longer monitor it every day, but we will constantly monitor it in the best possible way, using ever larger telescopes. The idea is to measure the path of the sun around the Earth from higher and higher positions so that this uncertainty area will continue to shrink. We are attempting to reduce the uncertainty in order to be able say if it will pass Earth safely or if there is any chance of a safe passage by the middle April.
What Happens in April?
The object will be so distant that we can no longer observe it. The James Webb Telescope then takes measurements. In March we will make a series of infrared measurements to get a better idea of the size and shape of the object. Then in May, additional measurements will be made. By then, it is most likely that you will be able say that we have proven that it is not going to strike Earth but that there is still a possibility that we may not be able eliminate it entirely. The most interesting part will be waiting until 2028 to observe it. We won’t let this time go by without taking action.
When was the last asteroid that had similar odds to hit Earth?
The last time was about 20 years ago, with the asteroid Apophis in 2004. Last time, was around 20 years ago with the asteroid Apophis 2004. It reached a few percent for a short period of time before the uncertainty area could be constrained.
This shows that 1% is a very unusual number, and we as experts need to take it seriously. With the probability at 2% it is still 98% probable that nothing will go wrong. It’s important to keep this in mind at all times. It’s something that deserves attention, but is not seen as a threat. We just need to learn more about it.
Asteroids of this size have they actually crashed on Earth?
This has happened in the past. In 1908, this happened in Siberia. A big explosion high in the air flattened 2,000 square kilometers worth of forest. This is consistent with an object of about 50 meters diameter plus or minus ten meters entering Earth’s atmospheric.
It is likely that the body was not a solid rock. This was a collection of smaller rocks. This explosion occurred several kilometers above ground level and caused a 2,000-square-kilometer forest to be flattened. Seismic waves were sent out and detected from a distance. People also witnessed the event from a great distance.
We do not know if there were any injuries in the accident. There is no news. The size and footprint of the destruction are comparable to that of a large urban area or city on Earth. This is the basic scenario we can expect.
A massive iron chunk believed to be about 50 meters wide, which formed the Barringer meteoric crater in Arizona, was another example that has not been recorded in history. It’s about a 1.2-kilometer wide crater. Imagine if this were to happen in a large city. The city would be very different.
This asteroid is estimated to be between 40 and 90 meters in size. There would be a huge difference in the amount of damage that something 40 m wide could cause compared to 90 m wide.
Absolutely. The 40-90 meter range is an estimate because at this time we don’t know the brightness of the surface. The current data indicates that it is more towards the 40- to 50-meter range. This is because I chose popular examples that are on the smaller scale.
However, asteroids are a very large object. Size matters a lot. The doubling of an asteroid’s radius means that it has eight times as much mass and energy. This is a big difference. On the lower end, at about 40 meters, the asteroid would threaten a medium-sized city. At 90 meters, however, the asteroid could be as large as the largest urban areas.
Since its discovery, why has the probability that 2024 YR4 will hit Earth increased?
This increase in size does not necessarily mean that an asteroid is more dangerous. Physical laws define the path of an asteroid. It is already known. Our knowledge of the actual path isn’t perfect.
You can compare the percentage to the size and uncertainty of the Earth. When you compare the fraction to the total area of uncertainty, you can see that the Earth’s size — which is within the uncertainty zone — is comparable to the area of uncertainty about where the asteroid might be at this critical time. This was about 1% of the total area when we reached international awareness.
Since then, the size has been reduced by about half. The size of Earth has remained the same. This means that Earth now occupies twice as much space in the region of uncertainty. Our estimate of the impact risk increased from 1% up to 2%. This does not mean anything has changed.
A 2% chance of missing is 98%. With our increasing knowledge, the uncertainty will continue to shrink. It is expected that the uncertainty will be so small that Earth will no longer fall within this region of uncertainty. The impact probability then will drop to zero.
If this is a flyby that’s relatively close to Earth, the probability of an impact will likely continue to increase on a modest trajectory. It’s still not a cause for concern.
According to the Torino Impact Hazard Scale, this asteroid is rated at Level 3 out of 10. What is the likelihood of that happening?
This is the first ever time that an object has been officially classified at Level 3 in the Torino Scale. Apophis was the only object to ever be classified at a higher level than 1. Apophis was classified as a 4, which simply means that it is a bigger object, because of its size. [Apophis’ estimated diameter is 350 meters. This is larger than asteroid 2024YR4].
What else should the public know?
Don’t panic! That is the main thing. It’s always good advice but this is a situation where it can be applied. This gives us the chance to show that as a world, we can rise above differences between people, countries and parts of Earth. We can come together and join forces to face a threat from outside.
It’s a challenge that can be overcome. It’s 98% certain that the object will not hit us, even if it was to head towards Earth. It’s not a big deal, and it gives us a chance to show how united we are on our planet.
