Joined: Fri Feb 24, 2006 1:20 am Posts: 2756 Location: Southern California, U.S.A.
Mars is roughly half the diameter of Earth, hence it has lower gravitational "pull" than Earth's. The velocity needed to escape its gravitational field is much lower than that needed to escape Earth's.
Mars is pockmarked from innumerable impacts by space debris, some in small meteoroidal chunks, some very large. In the more violent impacts Mars rocks have been thrown upward with such force they actually escaped the planet's gravitational field and went into Solar orbit. Over time some have been "captured" by Earth gravity as tiny moonlets (meteoroids) and they eventually lose orbital energy and fall inward toward the surface.
Unlike Mars, Earth is protected by an atmosphere, so most of the smaller ones burn up before they reach the surface. Larger masses can survive the trip and a few Mars rocks reach the surface as meteorites.
"Earth meteorites" on other planets no doubt exist. Our planet also has a violet impact history and some really huge space visitors have hammered us with unimaginable force. Consider the Chicxulub impact in the Yucatan that's often credited as the cause of dinosaur extinction. The crater is huge, some 110 miles in diameter, and it's far from the largest known. I'm sure there are plenty of "Earth asteroids" cruising around the Solar System and that many have been captured by other planets.
Because Earth, unlike Mars, has abundant rainfall and an active weather system, evidence of older impact craters has been eroded and erased. Many new ones have been identified and are only visible from Earth orbit. But even the mighty sandstorms on Mars can't do more than slightly obscure the fearsome cratered evidence of its violent past.
violent meteorite impacts on a planet might project rock chunks from the surface of the planet into space, then these rock chunks will travel into space, and sometimes they will eventually fall on another planet. This is why we sometimes find rocks from luna or mars at earth surface. Cool, uh?
Mars is roughly half the diameter of Earth, hence it has lower gravitational "pull" than Earth's. The velocity needed to escape its gravitational field is much lower than that needed to escape Earth's.
Mars is pockmarked from innumerable impacts by space debris, some in small meteoroidal chunks, some very large. In the more violent impacts Mars rocks have been thrown upward with such force they actually escaped the planet's gravitational field and went into Solar orbit. Over time some have been "captured" by Earth gravity as tiny moonlets (meteoroids) and they eventually lose orbital energy and fall inward toward the surface.
Unlike Mars, Earth is protected by an atmosphere, so most of the smaller ones burn up before they reach the surface. Larger masses can survive the trip and a few Mars rocks reach the surface as meteorites.
"Earth meteorites" on other planets no doubt exist. Our planet also has a violet impact history and some really huge space visitors have hammered us with unimaginable force. Consider the Chicxulub impact in the Yucatan that's often credited as the cause of dinosaur extinction. The crater is huge, some 110 miles in diameter, and it's far from the largest known. I'm sure there are plenty of "Earth asteroids" cruising around the Solar System and that many have been captured by other planets.
Because Earth, unlike Mars, has abundant rainfall and an active weather system, evidence of older impact craters has been eroded and erased. Many new ones have been identified and are only visible from Earth orbit. But even the mighty sandstorms on Mars can't do more than slightly obscure the fearsome cratered evidence of its violent past.
That is fascinating, I never knew there were meteorites from Mars. Thank you for that tidbit!
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