Google reports: Impact Details Object: Spent Falcon 9 upper stage from a January 2025 launch Mass: ~4,000–4,500 kg (4–4.5 tons) Speed: ~8,700 km/h (5,400 mph) Expected Crater Size: 20 to 30 meters (65 to 100 feet) wide I’m wondering if we’ll see a meteor shower in the days/weeks afterwards? What about the existing missions on the moon? Bob Wilson
meh. The moon doesn't have much of an atmosphere but it DOES have gravity - so I'm thinking that it's not going to be like the Remulakian rescue vessel accidentally chipping off a massive piece of rock while extracting the Conehead family from Earth. Falcon's upper stage will come sauntering in at something like 2.5km/s - and that's not too shabby but it's at least an order of magnitude slower than the hunks and chunks that caused most of the other craters. Since lunar escape velocity is 2.38 km/s, and Elon's lunar litter might be going a little bit faster - could any ejecta actually escape? Nah. It will make yet another crater, but the old "what goes up" rule will apply here.
I imagine that some large chunks left at >2.38 km/s as impactor arrived at 2.41. Earth's gravity well will eventually capture some of those which seems a good thing. Interesting and unfortunate if other chunks find their ways to some of Earth's Lagrangian points. Those now proving useful for astronomy.
Source: ‘Spectral lines’ and a giant plume: what science saw when the SpaceX rocket hit the moon | The moon | The Guardian Nasa and its Lunar Reconnaissance Orbiter probe and South Korea’s Pathfinder Lunar Orbiter are planning to take images of the site after impact, which may show the wreckage of the rocket, but it could take days to receive that information. However, the manner in which the impact plume interacted with the sunlight allowed astronomers to glean some clues about its composition. The sodium gas in the spectra is believed to have originated from the lunar soil, while the traces of lithium may have come from the rocket stage itself, Schmidt said. Bob Wilson
South Korea space agency shares moon images: South Korea space agency shares Moon images after SpaceX rocket debris crash
I'm having difficulty imaging how it could create an organized shower big enough for us to detect. It would seem that many eventually destined for Earth, would get spread out over geologic time, not mere weeks or years. The moon gets hit with natural rocks of similar kinetic energy (typically lower mass but much higher speeds) on average every week. Those don't seem to have affected any known existing or past missions.
Welcome to impactor class This image is for Earth but can be applied with minor changes for Moon Because Moon has smaller cross section and sits in/creates a small gravity well, the Moon graph blue line would be shifted in which direction? Any responses ? Answer is directly downward. If anyone really wants to ace this class, estimate how far downward and show your work. Other change for moon is that small in-comers are not melted by atmosphere. Even crumbs interact energetically with surface. This has implications for moon structures built in future. There may be enough information to estimate influx to, say, a proper sized Moonville (One km2) per decade. Image is based (I suppose) on somehow averaged arrival velocity. That may be best we can do? Range is about 10 to 70 km/sec. No distinction made between comets (mostly water ice) and proper rocky metallic impactors. Above atmospheric penetration size that may not matter on Earth (they do not spend enough time in atmosphere to 'notice' it). To Moonville it may not matter at all. Ufda. -- Not about the moon, but red curve is based on earth's observatories' work. Notice that largest are over-detected, and smalls are under-detected. For tree enthusiasts (I'm in) Tunguska was particularly notable for leveling a large area of boreal forest.
According to the above chart, the red line is based on discoveries to 19 January 2009. According to JPL's Center for Near Earth Object Studies, about such 6000 objects of all size were known then, a figure that approximately matches where that chart's red line intercepts the Y-axis scale markings. As of today, known objects now exceed 42,000, which should raise the portion of the red line to the left of the blue line -- a lot in absolute terms, but only a small bit on the chart's logarithmic scale: In contrast, the number of very large objects, greater than 1 km, has increased far less, from about 730 in 2009 to 875 today. More than 3000 new objects are being discovered each year now, but the rate of new >1km objects has fallen to just 2 per year, suggesting that most of the big boys have already been found. They are now finding mostly small- and medium-sized rocks. The new Vera Rubin instrument should be a game changer, greatly increasing the discovery rate. News earlier this year from just its testing phase indicated that it had already found over 11,000 new asteroids, but only 33 of them are in this Near Earth Object category, the rest are more distant.
There will be at least one 'A' in Impactor class Vera Rubin Observatory is super duper, but being ground based, is blind to 'sun-side' impactor approaches. Those persist as potential surprises . I hope for more research towards deflecting 100 meter (500 year) impactor size to high Earth orbits. Mining opportunities for $$$ gazillions. I mean metallic meteors, not chondrites or snowballs. -- Back to moon, estimating summed impactors' kinetic energy per km2 area per decade remains interesting, as Moonville will eventually happen. All of Humans' lunar impacts are small in comparison.
The Moon's diameter is about 27% that of Earth. Raw cross sectional target area would be the square of that, or 7.4%. But adjusting for the depths of the corresponding gravity wells complicates the answer, increasing the effective target areas as gravity bends many incoming trajectories to strike, when they'd miss a flat paper target of negligible mass. And increasing the Earth's capture rate more than the Moon's capture rate. The effective increase also depends on projectile speed before it comes into that gravity well, with higher speed object paths bent less. The moon's mass is a mere 1.2% that of earth, but I don't believe the asteroid capture rate changes by direct portion, but by something much less drastic. I don't yet have any final answer, so no A+ for now. -------- P.S. Above I was thinking of total impact rate. Adjusted to per km^2, the differing gravity wells mean that the Moon will have a somewhat lower basic impact rate per unit area than Earth, but not by anywhere close to their 81-to-1 mass ratio. OTOH, our atmospheric shield does protect us from the far more common "small" ones, so any station on the Moon with less than (very roughly) a ton of shielding per square foot -- 10 metric tons per square meter -- will suffer a higher rate of serious damage than anything on Earth.
According to this page: Orbitviewer Rubin's discoveries have now increased to about 35,000 new objects. I don't yet see how many are NEOs, but a quick plot clearly showed more than the 33 of the earlier press release.
