Birth of our Moon

[DarthDooku]

There is a theory that a Mars sized object collided with Earth, sending up an enormous amount of debris which orbited the Earth and eventually came together to form our moon. I recently saw on the science channel a picture of Mars where it looked like it had a big scar on the side. I was thinking maybe it was actually Mars itself which rubbed up against the Earth taking a chunk out of the Earth and leaving a scar on Mars.

 

Its not as good a picture as i saw, but here is the "scar" i was thinking of. Its the wide canyon-looking feature that is in the lower center area that spreads out horizontally. In the other pictures i saw on tv, it is much deeper than it appears in this picture.

 

http://www.unet.univie.ac.at/~a9503672/astro/grafiken/solar/mars.jpg

[Cap'n Refsmmat]

Such an impact like that would also blast Mars to smithereens, since it is smaller than Earth. Enough impact to create the Moon would probably destroy Mars-and, I believe, the scientists were making the estimate for a head-on collision, not a glancing blow.

 

Nice idea though.

[ecoli]

I don't think an object as big as mars would be needed to make the moon. If an object collided with the earth to make the moon, wouldn't it need to be only the size of the moon. (1/6 the size of earth)

[[Tycho?]]

There is a theory that a Mars sized object collided with Earth' date=' sending up an enormous amount of debris which orbited the Earth and eventually came together to form our moon. I recently saw on the science channel a picture of Mars where it looked like it had a big scar on the side. I was thinking maybe it was actually Mars itself which rubbed up against the Earth taking a chunk out of the Earth and leaving a scar on Mars.

 

Its not as good a picture as i saw, but here is the "scar" i was thinking of. Its the wide canyon-looking feature that is in the lower center area that spreads out horizontally. In the other pictures i saw on tv, it is much deeper than it appears in this picture.

 

http://www.unet.univie.ac.at/~a9503672/astro/grafiken/solar/mars.jpg[/quote']

 

 

Uh I think not. For earth and mars to brush up against eachother yet end up in their current orbits, they would have to be moving extremely quickly not to simply stick to eachother or fall into orbit around eachother. At such huge speeds one or both of the planets would probably break up into smaller peieces.

 

And if it hit earth hard enough to blow a moon sized mass off the surface and into orbit, then I think it would do more to mars than a comparitively tiny superifical mark. Its like getting a scratch from being hit by a train.

[Ophiolite]

I don't think an object as big as mars would be needed to make the moon. If an object collided with the earth to make the moon, wouldn't it need to be only the size of the moon. (1/6 the size of earth)

Very detailed simulations have been carried out on this hypothethis that place constraints on the size, velocity and angle of attack of the object. After impact only 10% of the ejected mass actually remains in orbit to form the moon. The rest heads of into the beyond. A substantial portion of the ejected mass is from the mantle, which is why the moon is quite light and probably why we have plate tectonics.