While Earth appears to be in the clear, it’s possible the Moon might not be so lucky. Asteroid 2024 YR4, discovered late last year, was initially thought to be on a potential collision course with our planet. Although that scenario has been proven highly improbable, astronomers say there is still a small chance the asteroid could strike the Moon in 2032.
Paul Wiegert, physics and astronomy professor in Western’s Faculty of Science, is an expert on asteroid dynamics and has been closely monitoring 2024 YR4. He spoke with Western News to share what’s known about the asteroid and what a potential lunar impact could mean.
Professor Paul Wiegert
Western News: What is 2024 YR4?
Paul Wiegert: 2024 YR4 is an asteroid that likely originated in the asteroid belt, between Mars and Jupiter. It’s approximately 60 metres across, about the size of a large building, and has a four per cent chance of hitting the Moon in 2032.
This asteroid was first seen in 2024 and given the provisional designation “2024 YR4,” as it awaits an official name. As usual, the discoverers of this asteroid will be allowed to suggest an official name, but there are some restrictions, and the entire process will be overseen by the International Astronomical Union. However, asteroids that pose a risk to the Earth undergo additional scrutiny, so it could be months or even years before 2024 YR4 receives an official name.
Why is this particular asteroid attracting so much attention?
PW: When it was initially discovered, there was speculation that YR4 might hit Earth in the near future. We now know that it’s not going to hit Earth at all, but there’s still a chance it could strike the Moon, and that would come with its own consequences.
What could be the consequences if 2024 YR4 were to collide with the Moon?
PW: If YR4 hits the Moon, it will be at about 13 kilometres per second, which is tens of thousands of kilometres per hour. At that speed, it’ll make a crater and release significant amounts of ejecta (moon rock). A lot of that material will fall back to the surface, which could pose dangerous risks to any astronauts nearby. This would be a particular concern given that NASA’s Artemis program is expected to have missions on the Moon at that time.
Also, a small fraction of moon rock can actually be blasted off the surface and head out into space. If the impact happens in the right place, a lot of this material could possibly end up being pulled in by Earth’s gravity. In this scenario, there could be serious risk to satellites and the International Space Station.
Should we be worried?
PW: No, that’s the short answer. I’m not worried and you shouldn’t be either.
The most likely possibility is that YR4 will miss the Moon entirely. But even if it does strike, there is no risk to Earth itself. The moon rocks that could potentially reach Earth will probably be millimetres or centimetres in size, which is the same size that creates shooting stars. The Earth’s atmosphere provides a very effective shield against these kinds of shooting stars. It’ll be beautiful to look at, but not dangerous at all.
As astronomers, we’re doing our best to try to detect and track these asteroids as quickly as possible. Currently, there are no known asteroids with any significant chance of striking Earth. There are many, many other things that are more dangerous to worry about – asteroids are not one of them.
Is this a rare occurrence?
PW: It’s uncommon, for sure. If YR4 hits the Moon, it will be the largest asteroid to have hit the Moon in about 5,000 years. It’s quite a rare event.
Will people at home be able to see any of the action?
PW: If the asteroid hits the Moon on the side pointing towards us, then yes. People at home will be able to see the explosion with small telescopes or even binoculars.
If ejecta is launched into space by the impact, fragments of moon rock could reach Earth in about three to seven days. At this point, we should also get to see quite a spectacular meteor shower.
Do we have any mechanisms to protect Earth from the threat of asteroids?
PW: We do. The best defence is always knowing well ahead of time that an asteroid is coming your way, because if you have 100 years to plan for it, you have a lot more options than if you only have a year. So, astronomers have been working on this for a long time, finding asteroids as quickly as possible and assessing them.
But let’s say we found one and needed to do something about it. In that case, we have only one system which has been successfully tested so far, the Double Asteroid Redirection Test, or DART. Basically, we send a spaceship to go and smack into an asteroid to deflect it. It’s kind of a simple idea, but it works. We now have the ability to deflect an asteroid that might be heading towards Earth.
