Asteroids don’t always need to head straight for Earth to draw global attention. The case of asteroid 2024 YR4 is proving just that. Once flagged for a potential Earth impact, this 200-foot-wide object has since been ruled out as a threat to our planet. But now, astronomers are monitoring a different possibility– one that puts the Moon in the line of fire.With a projected 4% chance of striking the lunar surface in 2032, the asteroid might not pose any risk to people on Earth, but the consequences of such a collision could still reach closer to home, especially for satellites and orbiting infrastructure.
Initial Earth threat ruled out
As mentioned in a recent report by Space(dot)com, asteroid 2024 YR4 was initially tracked with a 1 in 43 chance of hitting Earth. That concern has now been cleared with fresh data, confirming there’s no risk to our planet. However, the focus has shifted to the Moon, which scientists say could be struck by the asteroid in less than a decade.Astronomer Paul Wiegert from the University of Western Ontario told Space(dot)com, “A 2024 YR4 impact on the moon would pose no risk to anything on the surface of the Earth: our atmosphere will shield us. But the impact could pose some danger to equipment or astronauts (if any) on the moon, and certainly to satellites and other Earth-orbiting platforms, which are above our atmosphere.”
An explosion unseen in Millennia
According to the report, if the asteroid does collide with the Moon, the impact is expected to be massive. Scientists estimate it would release energy equivalent to 6 million tons of TNT, making it the most powerful lunar impact in nearly 5,000 years.As per Wiegert and as quoted by Space(dot)com, the collision would create a crater about 1 kilometre wide. While most of the debris from the impact would fall back to the Moon, a small percentage– estimated at between 0.02% and 0.2% – could escape into space.
Lunar debris could threaten satellites
Though the escaped fraction may seem small, it could translate to 10–100 million kilograms of lunar material. This debris could pose a serious challenge to objects in Earth’s orbit.“The YR4 impact, if it occurs and if it occurs in a favorable location, could produce a flux of meteoroids 10 to 1,000 times higher than the normal background for a few days,” Wiegert said, as quoted by Space(dot)com.
As mentioned in the report, the fragments would travel at around 22,400 miles per hour (10 km/s) – slower than regular meteors but still fast enough to damage satellites or space-based assets.
Earth’s atmosphere offers protection
Despite the volume of debris, Earth’s surface remains well protected. “The debris will burn up in Earth’s atmosphere. We don’t expect there to be many pieces large enough to survive passing through Earth’s atmosphere,” Wiegert said.He added, “A rock would have to be 3.3 feet (1 meter) or more in diameter to survive entry, but we expect most of the debris to be inches or smaller.”While ground-based life is safe, the debris could continue orbiting Earth for years, raising concerns about long-term satellite safety.
Does this call for a new risk scale?
Given the possibility of indirect space hazards, some have raised questions about the need for a system to evaluate such events. But experts say a new scale isn’t necessary.Richard P. Binzel, the planetary scientist at the Massachusetts Institute of Technology, told Space(dot)com, “No, the indirect consequences are too varied to compress into a single scale.”He explained further, “The Torino Scale is all about whether a passing asteroid merits attention in the first place, and of course, most asteroids don’t.”Binzel also underlined the importance of tracking asteroids accurately. “What one can control, by obtaining more telescopic measurements, is determining with certainty whether you have a hit or miss. After all, at the end of the day, an object either hits or misses. The answer is deterministic.”
Key updates expected in 2028
Astronomers expect a clearer picture in 2028, when asteroid 2024 YR4 will once again come into view. Until then, the current probability of a lunar impact remains at 4%.“Now we wait. There is, as of right now, about a 4% chance of asteroid YR4 hitting the moon, and we probably won’t get this number updated until the asteroid returns to visibility in 2028,” Wiegert said, as quoted by Space(dot)com. “At that point, we should know pretty quickly whether or not it will in fact hit the moon. The whole event would be exciting to watch in binoculars or a small telescope.”As per the Space(dot)com report, the study has been submitted to journals of the American Astronomical Society, with a preprint available on the online repository arXiv.