Stargazing What explains the Luna impact gap?

[Janus]

Surely the shadowing effect is due in very large part to the Earth's gravity well, not the Earth proper.

I'd say it's analogous* to the conjecture that life in a given star system may be greatly dependent on having a Jovian superplanet whose huge gravity well sweeps the system clean of potential extinction-level bodies. It wasn;t Jupiter proper that cleared out the comets...

*not saying it's the same mechanics, simply the implication that gravity wells are a primary factor in the orbital mechanics of bombardment.

The "target" the Earth makes is defined by the impact parameter, which itself depends on the velocity of the approaching object. So for example, if we assume that an object was "sneaking up" from behind the Earth in its orbit at a relative velocity of 10 km/s*, then the impact parameter expands out to 1.5 Earth radii. Drop that incoming velocity down to 5 km/s and it expands out to nearly 2.5 Earth radii

*initial velocity, not taking into account the effect of the Earth's gravity. (though in reality it's a bit more complicated than that. Say we start with such a body coming up behind the Earth. As the Earth's gravity begins to pull on forward on it, it gains orbital energy with respect to the Sun and it climbs to a higher orbit, but a higher orbit is a slower orbit, so its actually loses relative velocity with respect to the Earth. )

 

[Bob who knows a bit]

The 0° longitude gap and the absence of recorded impacts near the poles are artifacts of the observing system . . . they simply did not look there. Please refer to

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150021386.pdf

Thanks to spareine for finding the document

BTW, your concern about the Earth's gravity well concentrating or deflecting impact on the Moon might be applied to the difference between impact counts on the eastern and western hemispheres although the normal flow of NEOs catching up with the Earth-Moon system or the Earth-Moon system catching up with the NEOs may be more important.

 

[Dragrath]

A few comments regarding lunar impacts since somone mentioned the glancing blow hypothisis I feel the need to argue the strongest model for the moon forming impact occurance is probably the synestia one since it removes the need for a "glancing blow" freeing up a far larger potential parameter space to reproduce the post impact Earth Moon system but I digress so back to the topic at hand. Yeah the bias here is primarily due to the exclusion of these regions though there is apparently a real measurable ge bias on the Moon as interestingly there does seem to be a significant increase in Asteroid impacts in our solar system over the last 290 million years.
https://www.sciencedaily.com/releases/2019/01/190117142042.htm

 

[Bob who knows a bit]

Dragrath the synestia hypothisis is interesting and may be accepted



There are the outliers: Venus backwards, Uranus on it side, us with a large moon, and the double dwarf planet Pluto - Charon L O L

We need giant telescopes (interferometers) in space to study other solar systems.

So far as the lunar impacts central gap and nothing at the poles - Occam's Razor . . . plus the paper from the people recording the meteor impacts

Isn't science "interesting"?