Space Rocks. How do they know?

Hopefully someone can offer a simple answer to this. for many years I have read stories and seen documentaries about meteorites they have found here on earth and that they have rocks from the Moon or Mars and various other 'identifiable' planets.
Here is a recent story...

EVIDENCE of life on Mars may have already arrived on Earth, hidden inside white meteorites made of sedimentary rock. That's the new hope, at least.
So far, all meteorites from Mars have been made of volcanic rock. But sedimentary rock, laid down in ancient Martian oceans, may be the best place to look for evidence of alien life, since water is a life-friendly environment.

White meteorites from Mars may hide evidence of life

So as the title suggests, I would like to know just how they can be so sure these rocks are not only from space, but exactly which body they came here from.


I dont doubt thier expertise, but it has me beat as to how confident they are about thier claims.

It is based on the chemical compostition of the rocks, each planet has a different compostion in the rocks present based on the environment around it, mars has a lot of iron mineral in the soils and rocks have rusted over the years to ferric oxide, giving the red colour to the planet, and if the meteorite from space contains the exact compostition of the metals and other minerals matching to that of mars, then it is a meteorite from mars, if not, they would have to search for other sources

[edit on 1/10/08 by peacejet]

Thanks.
I understand how that works...to a point, but we have only recently 'been' to Mars to confirm the chemical make up, yet they have been making the claims for some time now. Also, what is to say there is not another planet (not necessarily in our solar system) or even a K.Belt object with a similar make up to not just Mars, but Venus or Mercury or even our moon as they have also claimed.

Okay, not to mention how does a rock escape the gravitational pull from mars? I am sure a rock would have had to start out very large in order to have burn off when it enters our orbit. Something large enough to leave Mars, travel across space, burn up in our atmosphere, would have had to been propelled by an outside force hitting Mars with a great impact. And if someone points out that Mars has less gravity than Earth...just think about how the protective bubble that carried the orbiters bounced off the surface, eventually coming to a halt.

reply to post by VIKINGANT


Very interesting question. I have been scouring a place on this 12-mile X 2-mile chunka rock we live on for more than a year. I believe it to be an impact crater, in spite of the nearly immesurable odds that an meteorite would impact such a small place. There are clues that determine the probability of a meteorite -- here's some info: www.aerolite.org...

Within that framework, it can be determined via light spectrometry, the basic composition (and possible atmosphere) of planetary bodies. The "Mars rocks" were consistent with what was fairly well determined about the surface of Mars. What is difficult for me to understand is ....... what caused these rocks to spewed from the surface of Mars and eventually land here. It almost seems to mandate a large, a HUGE strike on the surface of Mars that put various particles in an expanding orbit. The odds of such particles/rocks eventually becoming independent of Mars' gravity, spinning off and landing on Earth seem............ astronomically large. That would seem to infer to me that there was such a GIANT impact that it liberated billions of such "rocks"...... on eccentric orbits. It's amazing to think about.

OR..... and I'm just saying...... OR NASA is full of beans. Still, I think their analysis holds water (pun intended).

Mars has, if I recally correctly, only 38% the gravity of Earth and any rocks making their way back to Earth were surely thrown off by an impact large enough to eject material from the gravity well.

The surface chemical composition should be readable from the spectrum of the reflected light. Of course, that is only the surface so if you want more you have to go there and dig.

reply to post by VIKINGANT


Every planet is unique based on the distance from the sun, for example the earth is unique for life, because it is in goldilocks zone, a zone surrounding the star where life can exist, venus is in the outer edge of the zone and mars is in the inner edge of the zone. The reason why I am saying this is to understand the uniqueness of the planets, so venus is too hot and mars is too cold and the earth is just right for life and this temperature determines, the way in which elements are formed, for example, mercury has a surface and core full of iron, which didnt rust, because of the lack of water vapour due to the vicinity to the sun, similarly the kuiper belt objects are too far away from the sun and are merely ice ball orbiting the sun, so, the composition of a rock from mars cannot be the same of that of the kuiper belt object.

Originally posted by Taledus
And if someone points out that Mars has less gravity than Earth...just think about how the protective bubble that carried the orbiters bounced off the surface, eventually coming to a halt.

Mars has less gravity than earth, considering the fact that the earth's gravity is used as a reference for this, that does not mean that there is no gravity at all, there is gravity and why the orbiters bounced off the surface is because of the velocity with which they strike the ground, it is like how you throw a ball on the ground and it bounces back at you.

reply to post by peacejet


Right, I understand that. I was thinking of simple physics. Simply put, an object large enough would have had to hit mars with great velocity in order to propell rocks larger than bowling balls out of Mars atmosphere.

Think of this analogy...if you were on the moon and shot a gun, the bullet would travel back to the moon by pull of the moon's gravity. Please don't ask for a source, I forget which physics class I was in at the time. But this, from what I understand, is an example conventional physics adheres to.

Since Mars would definately have more gravity and atmosphere than the moon, I would logically guess the object that hit Mars to send us rocks would have had to have been huge...forgive my lazyness ATM without the math.

reply to post by Taledus


I understand your question, ill explain that.

Consider the bullet is travelling parallel to the moon, the gravity would bend the bullet towards the moon, and if the gravity overcomes the speed of the bullet, it comes crashing to the moon, if not it just changes path. The same thing occurs to asteroids and all other objects in space, and this same principle was used to propel the various spacecrafts to the outer planets, with the help of jupiter, called as gravity slingshot.

And regarding the high velocities hitting of meteorites hitting mars, jupiter is the protector as well as the destroyer of the solar system, it prevents many asteroids from hitting our earth, by deflecting its orbit with its massive gravity, and sometimes, the opposite can also occur, it can deflect the asteroid towards earth, so, it might have deflected asteriod towards mars and it might have imacted the surface and in the impact launched the debries to outer space.

I've always thought it was the tiny bits of atmosphere trapped in the rocks that let them be identified location wise but I guess the composition would probably give the right signals to look a little deeper.

Makes me wonder if there any completely normal looking rocks from space we have just not paid attention to.

Originally posted by peacejet
reply to post by Taledus

 

I understand your question, ill explain that.

Consider the bullet is travelling parallel to the moon, the gravity would bend the bullet towards the moon, and if the gravity overcomes the speed of the bullet, it comes crashing to the moon, if not it just changes path. The same thing occurs to asteroids and all other objects in space, and this same principle was used to propel the various spacecrafts to the outer planets, with the help of jupiter, called as gravity slingshot.

And regarding the high velocities hitting of meteorites hitting mars, jupiter is the protector as well as the destroyer of the solar system, it prevents many asteroids from hitting our earth, by deflecting its orbit with its massive gravity, and sometimes, the opposite can also occur, it can deflect the asteroid towards earth, so, it might have deflected asteriod towards mars and it might have imacted the surface and in the impact launched the debries to outer space.

Right, I understand about a gravity slingshot...but I also understand if you were on the moon, fired a bullet perpendicular to the moon's surface, it would be pulled back in by the moons gravity. Now, apply that same example to Mars, whereas a meteor (travelling from any direction) impacts the surface of Mars, thus propelling a rock off the surface of Mars perpendicular to it's surface.

Now take into account how much energy the rock would need...the moon has less gravity, and less escape velocity than Mars, and a bullet would need to travel (I believe) over 2km/sec just to escape the moon...bullets travel less than half of that, so it is then not possible on the moon, and definately no possible on Mars taking these calculations in account.

I hope that makes sense.

Now, I might run the numbers later, but just guestimating right now, a rock larger than a bowling ball would need to travel faster than the speed of light in order to possibly reach Mars escape velocity. I am having trouble finding a reliable source for the gravity measurment on Mars for the equation, so if someone knows a source, please let me know.

And to note peacejet...I am not trying to be a smart@$$...this is just something that logically is not possible running the numbers in my head right now

Originally posted by Taledus

Originally posted by peacejet
reply to post by Taledus

 

Now, I might run the numbers later, but just guestimating right now, a rock larger than a bowling ball would need to travel faster than the speed of light in order to possibly reach Mars escape velocity.

The earths escape velocity is 11.2 km/s(~17000 MPH), and the escape velocity of mars is 5.027 km/s (11,245 MPH), and nothing in this universe can travel faster thatn the speed of light because, according to einsteins mass-energy equivalence equation, if any object reaches the speed of light, its mass becomes infinity, and to escape mars's gravity you need not travel at the speed of light, as mentioned earlier, 5.027 km/s.

[edit on 2/10/08 by peacejet]

E=MC^2

I wasn't talking about the object leaving the surface of Mars, I was talking about the one hitting it...should have used two different objects, but had the bowling ball in my head. In order to provide enough energy, an object the size of a bowling ball should be travelling faster than the speed of light, in order to propell a bullet from the surface of Mars 5.027 km/s upon impact on the surface. I understand about Einstein's mass-energy equivalence equation, but taking into account all the variables I would guess that there is no way an object's mass could become infinate in order to do this.

It has been years since I've worked with physics (amature), and I believe that I may be missing something, so if someone knows of the equation to use to determine the Mass and Energy needed by an object to impact the surface of Mars to propell a bullet into space with enough velocity to escape Mars, please feel free to share.

How rocks may be ejected by impacts is a subject that's been well studied

For example:

www.sciencemag.org...

www.sciencemag.org...

Some of the larger impacts on Earth would most likely have ejected material into space as well. I've a feeling a supervolcano eruption might also be capable? Though obvious much smaller stuff that would not survive reentry as a meteorite.

reply to post by Taledus


Not that formula, one of the special cases,

m=mo/square root of 1-v^2/c^2

where mo is the mass of object at rest and m is the mass of object at the velocity v.

as you can see in the formula, if v=c, v^2/c^2 becomes 1 and 1-1 becomes 0 and mo/0 becomes infinity.

@ Essan:

The links bring up pages, but not the abstract. In order to get the pdf you have to sign up . Any way you could just post the abstract?

@ peacejet:

Star for that because I have never came across the equation that makes mass infinate.

However, is there an equation that demonstrates (m sub 1) * velocity * energy * impact = the velocity for (m sub 2)...that doesn't make sense to me, and probably wont to you, but you get the idea. I have been searching all of my links and scouring google for the special equation which determines the energy object 1 needs when entering an atmosphere, and on impact can hurl a bowling ball past Mars escape velocity.

Now, I keep using the bowling ball, but I thought about this...most bowling ball sized meteors burn up on entry into the atmosphere, thus, no space rock here on earth. Got any clue how large an object has to be in space for it to still be a rock after burn-entry into the atmosphere?

I think that you are saying about the law of conservation of energy, though two parameters of your formula match that of kinetic energy,

K.E=mv^2*1/2

I cant understand the energy and how can impact be multiplied, are you in any in any way telling the impact velocity.

If so, you can change the formula you mentioned to kinetic energy as,

m1v1^2*1/2=m2v2^2*1/2

Which you can mention as the energy transferred from the impact rock of mass m1 to another rock m2 which is launched in orbit, but, the energy transfer is not perfect, there is conversion to other forms of energy.

And the velocity and mass are variable, according to need, so you can add the conditions to the martian surface.

And regarding how large a meteor has to be escape entry friction, I dont know that, but a rough estimate would be about half a kilometer long would be enough to survive the atmosphere.

[edit on 2/10/08 by peacejet]

Originally posted by peacejet

I cant understand the energy and how can impact be multiplied, are you in any in any way telling the impact velocity.

[edit on 2/10/08 by peacejet]

No, I am not even trying to acertain the impact velocity, nor the mass...I am simply using logic to figure this out because right now my head hurts from all the variables involved

I might get back to this today sometime...I guess I wasn't stating my question clearly.

Edit: OMG!!! I just realized that I have completely taken over this thread...I apoligize to the OP for that.

[edit on 2-10-2008 by Taledus]