Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Asteroid, Meteorite, Meteoroid, or Meteor?

  1. May 1, 2012 #1
    So I know a meteoroid is the small thing floating in space while an asteroid is the large one. I know a meteor is the streak of light a meteoroid creates as it falls through the atmosphere and a meteorite is what remains after the impact on the Earth. Also, that meteorites can sometimes be produced by the impact of an asteroid. However, with this different terminology for the different parts, it leaves some naming questions in my head. I'm sure there are other answers that could be correct other than the ones I provide:

    1) Does the light from an asteroid falling through the atmosphere count as a meteor?

    2) Is the small rock still considered a meteoroid when it's a foot away from hitting the surface? After all it's no longer in floating through space but it also has not collided yet.

    3) Would you call the impact a meteoroid impact, meteor impact, or meteorite impact? Meteor impact doesn't seem likely. Meteorite impact seems the most reasonable until you consider the fact that no meteorite might be left.

    4) If an asteroid survived the fall to Earth more or less intact (somehow, maybe it had some unbelievable trajectory that made the impact relatively slow and was a piece of solid iron) and it plopped down to become a large hill or small mountain, would it still be called a meteorite even though it was mostly an intact asteroid?
     
  2. jcsd
  3. May 2, 2012 #2

    PhysicoRaj

    User Avatar
    Gold Member

    I have heard of only meteor showers but not asteroid showers.

    It is considered a meteor. Because it is neither in space nor on ground. It's in the atmos.

    Unfortunately, it is called meteor impact.

    Yes. It is still a meteorite. (No meteoroid/asteroid can hit the ground without being absolutely intact. If you see a large one, then the meteoroid would have been much larger. An absolutely pure solid iron meteoroid is exasperatingly rare. All meteoroids containing iron are called stony-irons, which contain more or less olivine rock).
     
  4. May 2, 2012 #3

    davenn

    User Avatar
    Science Advisor
    Gold Member

    not quite.

    there are 3 main classes of meteorites ( and a few more sub-classes)

    there are....

    Irons - pretty much pure nickel/iron
    Stoney Irons - as name suggests a mix of stone and iron
    Stones - quite a number of sub-classes under 2 main classes Chondrites and Achondrites

    cheers
    Dave
     
  5. May 2, 2012 #4

    davenn

    User Avatar
    Science Advisor
    Gold Member


    he wasnt asking about showers .... really the difference between a meteor and an asteroid is kinda academic. its really just a matter of size. I couldnt find anything on a size definition say... <100 m its a meteor >100m its an asteroid will keep looking
    Also most asteroids have 'calculable/relatively fixed' orbits where as meteors have random motions through space.
    When a meteroid or asteroid enters the Earth's atmosphere, it ignites, creating a visible streak of light called a meteor. If the object doesn't vaporize completely and crashes into the Earth, it's called a meteorite.
    That answers a couple of your questions :)

    Dave
     
  6. May 2, 2012 #5

    davenn

    User Avatar
    Science Advisor
    Gold Member

    well after searching many pages I came across this comment.....

    "Meteoroid
    •A meteoroid is a small rock or particle of debris in our solar system. They range in size from dust to around 10 metres in diameter (larger objects are usually referred to as asteroids)."

    so around 10 metres diameter is a rough indication of difference between meteoroid and asteroid.
    BUT NOTE --- Regardless of if its an asteroid OR meteoroid, once it has entered the atmosphere of a planet its called a meteor, regardless of size.

    Dave
     
  7. May 3, 2012 #6

    PhysicoRaj

    User Avatar
    Gold Member

    But my question is how a meteoroid can be made of such purity of metals, I mean where do they get them from???
     
  8. May 3, 2012 #7

    davenn

    User Avatar
    Science Advisor
    Gold Member

    The nickel-irons are generally thought to be the core of an asteroid/planetoid that had broken up
    Just as the core of the earth is also predominantly nickel-iron

    there are zillions of links if you do a google search

    here is just one of them


    cheers
    Dave
     
    Last edited: May 3, 2012
  9. May 3, 2012 #8

    PhysicoRaj

    User Avatar
    Gold Member

    Great!
    But will the temperature during entry into the atmos rise up to the boiling (or even melting) point of either of those metals??
     
  10. May 3, 2012 #9

    davenn

    User Avatar
    Science Advisor
    Gold Member

    ohhh yes ... the temperatures get to several 1000 degrees C. The effects of that temperature can even be seen on one or two of my meteorite samples
    consider this... the typical velocity of incoming meteors is ~ 30 - 40 km per sec !!
    of course the friction with the atmosphere will slow that a bit, but its still going to hit the ground at many km's / sec.
    the larger objects say ~ 1 metre and larger in diameter and you work out the kinetic energies involved ... they are huge and for the larger meteors the energy levels are in the megatonnes of TNT range ie... huge nuclear bomb sizes.

    my collection

    have a look particularly at the first sample in the 4th row down.
    The Sikhote-Alin, Russia one click on images to get a larger view :) You can see the deep crack/scouring caused by the heat of entry.

    I dont know what country you live in, but if its the USA, you should get to Meteor Crater in Arizona some time. I have been there a couple of times during visits to the USA. Standing on the rim of the crater is an awesome experience, knowing that ~ 50,000 yrs ago that a ~ 50metre diameter lump of nickel-iron punched its way through the atmosphere and blasted a hole ~ 1.2km diameter and ~ 170 metres deep. They estimate the energy released by the impact to be ~ 10 megatonnes
    have a look at Meteor Crater in wikipedia for pics and more info :)
    you will see some of my meteorite samples from there on that my collection link above

    We have a number of meteor craters here in Australia too, tho I havent had a chance to visit any of them yet, they are in quite remote locations. I do have a couple of Australia meteorite samples tho

    cheers
    Dave
     
  11. May 4, 2012 #10

    PhysicoRaj

    User Avatar
    Gold Member

    You have got a pretty unique and amazing collection. The Chicxulub might have also formed by the impact of a nickel iron, becuz it's 300 km in diameter!
     
  12. May 4, 2012 #11

    davenn

    User Avatar
    Science Advisor
    Gold Member

    This is just my thoughts --- dunno if there's any info out there some where --- prob. is....

    I suspect you will find the majority of craters will have been formed by nickel-iron impacts. Reason -- stones and stony irons tend to break up very easily on entry to the atmosphere. Where-as the N/I's, tho loosing a respectable percentage of their mass, tend to survive entry.

    Dave
     
  13. May 4, 2012 #12

    PhysicoRaj

    User Avatar
    Gold Member

    Right. Thanks.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Asteroid, Meteorite, Meteoroid, or Meteor?
  1. Green Meteor (Replies: 3)

  2. Meteor Shower (Replies: 1)

Loading...