Hi, I thought I’d share this here since it isn’t being covered by any news sources. It’s mostly my own research and calculations, so it could be completely wrong, but I’m fairly confident it’s correct.

Most of you probably heard about the asteroid 2024 YR4, which briefly reached a 3.1% chance of Earth impact before its orbit was further constrained and the chance dropped to zero. What you may not have heard is that the chance of lunar impact has actually been steadily rising. No organization is currently reporting lunar impact statistics, so I’ve been calculating the probability myself. I’ve created a Desmos calculator that you can easily plug the approach data from NASA into. As of now it’s sitting at 1.94%, with the nominal approach being less than one lunar radius from the surface of the Moon (just 0.058 sigma from the closest approach).

This is the impact corridor for the Moon, as viewed from Earth. An impact on the near side (very likely) would be visible for an entire hemisphere of the Earth, including North and Central America, the eastern half of Asia, and Australia. Map of locations where the Moon will be visible at the time of impact. I’m not sure exactly how bright an impact would be, but a 45 kg asteroid caused a flash clearly visible to telescopes during a lunar eclipse back in 2019, so I expect an asteroid about 5 million times larger would be quite the show.

A 1.94% chance is still very small, but I’ll be keeping my eyes on the data and crossing my fingers for a lunar impact!

  • LostXOR@fedia.ioOP
    3·
    3 days ago

    Sure thing!

    D_nominal, D_min, and D_max represent the most likely, minimum, and maximum (well technically not maximum, just 3 standard deviations from most likely, of which 99.7% of trajectories will fall within) distance 2024 YR4 will pass from the center of the Moon (NOT the surface). They’re taken from the linked NASA website. R_moon is the radius of the Moon.

    L_impact is length of the impact corridor (the line where 2024 YR4 could impact the Moon). Since it doesn’t pass through the center of the Moon, it’s not simply 2*R_moon and so we need a simple formula to calculate it from R_moon and D_min.

    P(x) is a probability density function; it’s the black curve you can see. It shows, for a given trajectory along the line of possible trajectories, how likely 2024 YR4 is to follow that trajectory. It’s shifted a bit from the center since the most likely trajectories are not exactly centered on the Moon. P_impact is the area of P(x) that falls within +/- L_impact, AKA the probability that the trajectory will intersect the Moon, AKA the impact probability.

    The rest is just some graphing stuff that doesn’t matter to the calculation.

    • keepthepace@slrpnk.net
      2·
      3 days ago

      AKA the probability that the trajectory will intersect the Moon, AKA the impact probability.

      (Disclaimer, I know close to nothing about these) Am I pedantic about a useless detail or does it significantly change the probability if we consider that an object may still impact the moon after “missing it” if it comes close enough to be captured and come back after a semi orbit? Or do the relative speeds makes this extremely unlikely?