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If that were to be directional I'd expect it to be easier to see from straight down, because then you wouldn't have the walls of the crater blocking the view of the inner part of the crater.
The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site.
"On March 17, 2013, an object about the size of a small boulder hit the lunar surface in Mare Imbrium," says Bill Cooke of NASA's Meteoroid Environment Office. "It exploded in a flash nearly 10 times as bright as anything we've ever seen before."
Anyone looking at the Moon at the moment of impact could have seen the explosion--no telescope required. For about one second, the impact site was glowing like a 4th magnitude star.
Thanks. That idea has less problems than some of my ideas, so that's good. I know seeing exoplants directly is nearly impossible because their reflected light is so dim compared to the bright sun they are so close to, so I sort of understand your train of thought regarding the new moon in that context. However, I wouldn't have thought the new moon and the sun are close enough for a long enough period of time to create such a gap in our observations, but I suppose it might be possible.
My guess is that all these impact were recorded in the shadowed part of the Moon, when it was in "half" or "crescent" phase. Recording impacts in the middle of the near side of the Moon would mean it was new or near new, and thus very close to the Sun. I take it that it's impossible to record impacts on the sunlit part of the Moon, and thus impacts in the middle when the Moon was full weren't recorded either.
About Lunar Impact Monitoring (NASA)
When we observe: Observations are taken between New and 1st Quarter Moon and between Last Quarter and New Moon, when the solar illumination is between 10 and 55 percent. These conditions yield 10-12 observing nights per month.
Yes, if you follow the explanation by Wildespace, it suggests that there is a wider occurrence of impacts, but they aren't reported/recorded because of the difficulty of observing them when the moon is close to the sun. It's probably the best attempt to explain it so far, but let's say no observations are made the night of the new moon due to proximity of the sun from our viewing perspective. By the next night, I would have expected enough separation to eliminate this problem and there would still be plenty of opportunities to observe impacts in the "empty" region so I'm still somewhat puzzled.
That doesn't really help us to understand why the impacts are concentrated in some areas and almost absent in others. It does support the contention that we've got a small part of the picture. The LRO doesn't see everything either.
So I wonder if perhaps there is a wider occurrence of impacts that have a more even spread?
Yes, Jupiter is sort of a big vacuum cleaner that tries to suck up a lot of debris going past it, including some objects which might otherwise impact other plants like Earth, so yes it diminishes the total number of impacts on other planets. I can't see how this could result in such an impact pattern on the moon.
I know that Jupiter deflects most of the impacts from Earth's atmosphere. I don't know if that partly answers your question.
Excellent observation, but as I said in the OP which perhaps I could have said more clearly, I think that can probably be explained by the plane of our solar system. The orbits of the 8 planets and the asteroid belt aren't all exactly in the same plane, but they are pretty close, close enough to partly explain this aspect of the pattern, I think.
Not only the middle, but south and north are also lacking in recorded impacts. Any explanations should also include those two areas.
As the OP source says, this is because the Lunar monitoring program began in 2005, and it's basically the observation of flashes of light. Some may involve the production of tiny craters but I don't know how many of these impacts could be correlated with the appearance of new craters recorded by the LRO. If the the size of the crater is less than the resolution of the LRO we won't see it but the specific impact referenced in the OP link says they might be able to find the crater with the LRO since they expected it to be 20m, but keep in mind they think that's the largest impact they've observed since 2005.
Further: The pic you brought, caption reads, "2005-2013 impact candidates".
Referencing an exclusive study of some sort? Not all craters are numbered, obviously…
Excellent point, and this is surely part of the explanation for the apparent pattern, which would make the impact density appear thinner in the center, but it doesn't quite explain the gap.
One thing that may help getting more impacts on the "sides" is perspective, as the area we see on both sides of the area without impacts is, in reality, much bigger than what we see on the projection of the Moon's sphere into a circle.
Yes it's the best candidate so far and may be part of the answer, however I'm not sure it fully explains the gap. It may be yet another part of the explanation and there's still another reason?
And I think that wildespace's idea is the more likely to be closer to the truth.
let's say no observations are made the night of the new moon due to proximity of the sun from our viewing perspective. By the next night, I would have expected enough separation to eliminate this problem and there would still be plenty of opportunities to observe impacts in the "empty" region so I'm still somewhat puzzled.
reply to post by BGTM90
Thanks for the reply. Now, look at this image of the Earth and the moon, and note that impactors can approach the moon from any angle:
Do you see the problem with saying Earth is blocking the impacts when they come at the moon from many different angles?