Probability of Asteroid 2024 YR4 hitting the Moon increases
- Reference: 1749577511
- News link: https://www.theregister.co.uk/2025/06/10/asteroid_2024_yr4_update/
- Source link:
[1]NASA said data from the telescope "improved our knowledge of where the asteroid will be on Dec. 22, 2032, by nearly 20 percent." The upshot is that there is now a 4.3 percent possibility that the asteroid will hit the Moon in 7.5 years' time, although it wouldn't alter the natural satellite's orbit.
From concept to cosmos: Webb engineers on the telescope that changed everything [2]READ MORE
When Asteroid 2024 YR4 was detected, scientists [3]reckoned it had a 1 in 100 chance of colliding with the Earth in 2032. As the weeks passed, and more measurements of the asteroid's trajectory were made, that figure gradually [4]increased before eventually being cut to almost zero.
However, there remains a risk, albeit small, that it might smack into the Moon. In April, NASA put the probability at 3.8 percent. Experts from NASA's Center for Near-Earth Object Studies at the agency's Jet Propulsion Laboratory in Southern California have now ncreased the probability to 4.3 percent.
According to NASA, "An international team led by Dr Andy Rivkin from the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, made the observations using Webb's Near-Infrared Camera in May."
[5]1.5 TB of James Webb Space Telescope data just hit the internet
[6]Ex-NASA Admin pick blames Musk ties for pulled nomination
[7]NASA doubles odds of Moon hitting near-Earth asteroid
[8]UK must give more to ESA to get benefits of space industry boom, says Brian Cox
Asteroid 2024 YR4 is now too far away to be observed with either space or ground-based telescopes. The next time it will swing into view will be in 2028, when scientists will be able to refine its trajectory further and reduce or increase the probability of a collision accordingly.
Since an impact with the Moon won't affect the orbit of the Earth's natural satellite, Earth-dwellers are unlikely to be affected by the impact. In the event that a permanent human presence has been established on the lunar surface, it would be tremendously bad luck for any residents to be affected.
[9]
Russia and China have announced plans for a human presence on the Moon, as has the European Space Agency (ESA). NASA had also planned extended missions to the lunar surface, but those plans are currently in disarray following a budget request that [10]cut the agency's lunar ambitions and a [11]response from lawmakers that aims to put some of them back. ®
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[1] https://science.nasa.gov/blogs/planetary-defense/2025/06/05/nasas-webb-observations-update-asteroid-2024-yr4s-lunar-impact-odds/
[2] https://www.theregister.com/2025/03/28/james_webb_interview/
[3] https://www.theregister.com/2025/01/31/asteroid_earth_impact/
[4] https://www.theregister.com/2025/02/19/2024-yr4/
[5] https://www.theregister.com/2025/06/09/jwst_open_science_data/
[6] https://www.theregister.com/2025/06/06/how_nasa_might_have_looked/
[7] https://www.theregister.com/2025/04/05/nasa_moon_asteroid/
[8] https://www.theregister.com/2025/03/06/uk_needs_to_contribute_more/
[9] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aEj_SmF8XQteZ4_g4EVlWAAAAsE&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[10] https://www.theregister.com/2025/06/02/nasa_isaacman_dropped/
[11] https://www.theregister.com/2025/06/09/us_lawmakers_nasa_response/
[12] https://whitepapers.theregister.com/
And the chance of it hitting the moon hasn't changed, just the estimate of the probability of it doing so.
I might not have a degree or masters or anything in astrophysics but if that asteroid did hit the moon then it would change its orbit. It might only change it temporarily by the size of a gnat's todger but it would change it!
The orbit won't change much. But depending on the speed difference other damage might occur, though a breakup is unlikely. But even a breakup won't affect the orbit much.
Hmmm... 2024 YR4 is about 60m across. The moon, at 1737km radius, is about 60000 times larger in diameter, so it'd have a volume about 2.2e+14 times greater.
The object is probably silicate, with a density comparable to that of the moon. So the moon's mass is probably (again) about 2.2e+14 times that of 2024 YR4.
Impact speed would be about 13.9 km/s. So the change in the moon's speed would be 13.9 / 2.2e+14 km/s = 6.3e-11 m/s. The component of the speed change that is perpendicular to the moon's velocity won't change anything much, but if the rock hits "head on", it will slow the moon by that amount, and if it hits the moon from behind, the moon will speed up by that amount. Either way, the change in speed will be permanent, and there will be a change in the orbital period (admittedly of the order of microseconds).
(Note that I'm simplifying things the orbital mechanics here. But the change in speed will be roughly as indicated above.)
Now we come to the difficult part of the problem (at least for me; I'm an astronomer, not an entomologist.) I don't even know if gnats have external genitalia.
The first hit when searching for "gnat penis size" was
https://en.wikipedia.org/wiki/Muggeseggele
"...a humorous Alemannic German idiom used... to designate a nonspecific very small length... it refers to a housefly's scrotum."
The problem is that the Interwebs have a great deal of information about human penis sizes, and not much about insects. I don't think they'll help. Let's try this another way.
Another search came up with various gnat sizes from 1/16 to 1/8 "inch". Not sure if that's US or International inches, but call it 2mm. Let's be generous to the gnat and assume it's well-endowed, with genitals 1/10 as long as that, or 0.2mm, or 2e-4 metres. I can weasel out here by pointing out that you didn't specify a particular type of gnat anyway; perhaps some of the larger ones would fit my guesstimate. (Or perhaps there's an entomologist lurking in these fora who can comment.)
So, after 2e-4 / 6.3e-11 = 3.2 million seconds, or about five weeks, the moon's orbit would have been diverged from what it otherwise would have been by roughly the suggested amount.
However, that's short-term thinking. After, say, a million years, the divergence will be about two kilometers.
Bravo!
This is why I read el Reg.
you didn't specify a particular type of gnat
Obligatory "African or European?"
Mine's the one with the mosquito repellent in the pocket...
James Web telescope ...
... wow is that still going? Hasn't the monkey in the White House not yet cut funding for it? I am surprised.
Seveneves from Neal Stephenson
reading that now. [1]Fits perfectly to this topic . But in reality it won't work this well.
[1] https://www.nealstephenson.com/seveneves.html
Correct me if I am wrong but, why does it matter? The moon gets hit hy asteroids all the time.
A fair question. There's no safety aspect here. It should be of some scientific interest, in that it'll give us a look a few metres below the moon's surface at freshly-exposed lunar material, and we may learn a bit about crater formation. We've gotten some knowledge of such things from looking at the craters of the upper stages of Apollos 14 to 17 (they were deliberately aimed at the moon), but this is much larger and heavier.
I would expect at least a few smallish rocks to be ejected into geocentric and heliocentric orbits, mostly the former. (Not lunar orbit.) Such rocks would eventually hit the moon again, or the earth, or be ejected into heliocentric orbits. If they hit the earth, and survive re-entry, and have the good grace to hit land rather than ocean, we get lunar samples without having to send astronauts (Apollo) or a sample retrieval probe (Chang'-es 5 and 6) to do the job.
In 2028, this object will be visible again, and we'll be able to compute a very precise orbit and will know with basically metaphysical certitude if it'll hit the moon. If it does, I'd hope somebody lands a seismometer on the moon between now and 2032 Dec 22. The Apollo missions left such (and measured moonquakes caused by the aforementioned upper stages). It'd be a rare opportunity to really learn something about the moon's internal structure.
(But I'm not getting my hopes up all that much yet. As noted, odds are still against a lunar impact.)
Percentage of a percentage is always a misleading way of presenting such information. :/