# What is the rate of ejecta deposited between planets?

• I
• swampwiz
In summary, there is a lot of talk about how many rocks are ejected from Mars each year, but it is hard to verify the claims. Scientific American reports that there are around 15,000 tonnes of rocks ejected from Mars each year, which is much lower than the 500 kg/year that the wokeists claim. However, the mechanism for ejection from a planet has to be a collision as some other mass comes in and collides with the surface.f

#### swampwiz

I was reading this (which is notable for its non-science content, but I am only referring to this part):
https://www.nationalreview.com/2020/11/wokeists-assault-space-exploration
... it is estimated that every year, approximately 500 kilograms of rocks ejected from Mars via meteoric impact land on our planet.
Is there a matrix that shows the amount that goes between the planets? (And here, I consider a moon to be a "planet".)

BUMP

No one has any idea?

It is not that simple. Try this search on google scholar 'estimates of planetary ejecta hitting earth'

Lots of good hits. You need to decide your parameters, the diversity of topics is not small.

I was reading this (which is notable for its non-science content, but I am only referring to this part):
https://www.nationalreview.com/2020/11/wokeists-assault-space-exploration

Is there a matrix that shows the amount that goes between the planets? (And here, I consider a moon to be a "planet".)

I would like to see references for their claims for the "billions of tons" and the 500kg/yr
They both seem extreme.

256bits
Let’s assume 10^9 metric tons. Surface density of 2000kg/m^3. That gives a 793m cube removed per year. That seems big, but not obscenely big. It could even be right. One is integrating over a lot of impacts.

I would also check out LPSC extended abstracts.

Let’s assume 10^9 metric tons. Surface density of 2000kg/m^3. That gives a 793m cube removed per year. That seems big, but not obscenely big. It could even be right. One is integrating over a lot of impacts.

I would also check out LPSC extended abstracts.

I could believe the figures for ALL meteorites, but just for Martian material, a bit hard to swallow

The rate for ALL meteoritic material is an avg of 50,000 tonnes / year
Wiki at ~ 15,000 tonnes / yr is very low compared to other sites

256bits
I would like to see references for their claims for the "billions of tons" and the 500kg/yr
They both seem extreme.

The numbers all seem to be huge but intuition can be very misleading.
The mechanism for ejection from a planet has to be a collision as some other mass comes in and collides with the surface. I would imagine there would have to be unusual circumstances for this to happen as most of the Kinetic Energy of the incident mass would be shared.

If the incident mass were to arrive from the Kuiper belt, say, it could have enough energy to eject a similar size mass into a much lower orbit - to collide with another inner (rocky) planet. But you would think that there would be far fewer rocks ejected than arriving. These events would all be pretty newsworthy on Earth but probably no one would be aware of an ejection event.

Having a rarified atmosphere and moderate gravity, Mars would perhaps be a better candidate for supplying rocks to Earth than the other way round. The Moon, even better.