Science junk:ALH84001 (a meteroite) was picked up in Antarctica in '84, supposedly from Mars,see (wikipedia),

Question

having been "rotating around the sun" for 16 billion years, (ejected from Mars' surface from an asteroid hit).

Then it "came into the gravitational pull of the earth" and ended up in Antarctica, (on the surface, I assume), 13,000 years ago, according to scientists.

Now all this rhetoric regarding "how it got here" is what I question.

The escape velocity (to have an object escape the gravitational pull of gravity) of the earth is about 17,000 miles per hour. It takes one helluva propulsion system to accomplish this.

Mars. being of much less mass/gravity requires about 40% less than that, say 8,000 mph escape velocity.

I cannot/willnot believe that an asteroid kicking up some rocks on Mars can result in those rocks being propelled into space at 8,000 mph (unless someone can prove to me with some viable figures to support such a theory).

There is nothing to prove that ALH84001 DID NOT come from the asteroid belt- between Mars & Jupiter.

Escape velocity needs answer.

2 hours later--sorry, I've read cites presented; still not convinced. May I call a lifeline?

I'm 75, amateur astonomer for 66, so I do have some knowledge re: astronomy.

Can someone please deal with the question in more specific terms?

I'm not trying to be stubborn; I'd just like a plausible answer. (not like Clinton's assumtive answer, w/o knowing anything about the subject at all).

Answer 1

C. How could ALH84001 get from Mars to Earth?

To get off Mars, ALH84001 must have left its surface going faster than Mars’ escape velocity, about 5 kilometers per second (about 11,000 miles per hour). The only known natural process that can get rocks moving so fast is meteorite impact--volcanoes can’t throw rocks fast enough. If a large enough meteorite or asteroid hit Mars, some rocks nearby on Mars’ surface would be blasted up faster than the escape velocity and could leave Mars completely. The best estimates are that an asteroid bigger than about 1/2-2 kilometers could launch rocks like ALH 84001 off Mars and into space.

After it left Mars, ALH 84001 orbited the Sun on its own, like a small asteroid. It started out with an orbit nearly like Mars’. But its orbit changed each time it passed close to Mars or collided with an asteroid. Also, gravity from the planets (especially from enormous Jupiter) slowly nudged ALH 84001 farther and farther from Mars. By chance, the orbit of ALH 84001 changed enough so that it came near the Earth's orbit. 13,000 years ago, the Earth and ALH 84001 collided.

Answer 2

Large impacts do that pretty regularly. You are ignoring the force at which an meteor hits the Earth... I'm sure you've heard that it hits so hard and fast that it penetrates the surface and then the ground above blows out from the shock. A fairly large impact would blow enough material away at a velocity that would easily escape the planet's gravity.

There is proof that Martian rocks did not come from the asteroid belt: Mars is comprised of different material than asteroids. All the scientists needed to do was compare the materials in the meteorite they found.

Answer 3

It has been calculated that the energy released by meteorite and comet impacts is tremendous.

The energy from the Tunguska impact in 1908 was somewhere in the order of 10 to 20 megatons of TNT (more than 4.2 x 10^16 Joules) and felled 60 million trees over 830 square miles.

Comparing these potential energies with impact-induced flows and energy transference obtained by the impact of iron and gabbroic anorthosite spheres onto a half-space of anorthosite at impact velocities of 5 to 45 km/sec has resulted in velocities of 20 to 45 km/sec imparted to crater ejecta.

20 km/sec equals about 45,000 mph. More than sufficient to achieve escape velocity on Mars (or Earth for that matter).

So while I share some of your skepticism as to the proof that these meteorites originated on Mars, the escape velocity of the planet is not a barrier to getting material off of Mars and into space where it can later impact Earth.

Answer 4

It does seriously depend on the mass and velocity of the colliding object. It is not out of the realm of imagination that an object of sufficient size and speed can collide with Mars and eject material at 8.5k or more m.p.h.. Although, it does seem a little contrived that the object wound up on our north pole, all by itself, after 16 billion years-post-impact. There would be theoretically a cloud of these objects and therefore many more specimens to be found in the area of discovery.

Answer 5

I cannot/will not accept that you could have completed High School without understanding the basic principle of action/reaction, and that you are unaware that when rocks in space hit orbiting planets in space, more rocks & stuff are expelled from those planets surfaces at far higher velocities than the escape velocity of those planets. Did you not watch the Shoemaker-Levy impacts on Jupiter?

Therefore I will award you the benefit of the doubt, and assume you are too young yet to have completed High School.

Answer 6

As you state that you "cannot/will not believe" something which is an established and accepted scientific fact then it's not worth the effort of explaining it to you as you will refuse to believe the explanation.

People with closed minds deserve the ignorance that they exist in.

Therefore, what I have written below is only for those with a sufficiently open mind to be prepared to accept facts without pre-judgment...
Large meteorite impacts create the force equivalent to many hundreds of atomic bombs and suffcient energy to easily cause relatively small chunks of rock to achieve the required escape velocity.

The chemical compositions of meteorites which originate from the asteroid belt (or from the Moon for that matter) are well known and established, as is the chemical composition of many of the surface rocks of Mars (through such processes as spectroscopic analysis). It has therefore been possible to establish the origin of the rock in question beyond all reasonable scientific doubt - leaving only those doubters who are unable to see beyond their own prejudices and ill-informed beliefs.

Answer 7

escape velocity is the speed in which the object needs to reach in order to get out of the force of gravity.