Expert: Tom Whiting - 1/11/2008

Question
Hello,

I was wondering, since most matter in the solar system seems to be revolving around the sun in the eliptic plane (same as the planets), does this mean that there is a much higher likelihood of meteors striking the equatorial area of the Earth, rather than the northern and southern areas? Do you have any info on this (or know where it can be found), like maybe some statistics?

Thanks a lot!
- Tue Sorensen, Denmark

Answer
Hi Tue,
Actually, most of the matter in the Solar System is IN
the sun, 99.86% of it in fact.  Yes, the remaining 0.14%
is mainly found on the ecliptic, but 0.1% is Jupiter itself, and the remaining 0.04% mass is everything else in the Solar System!  So the mass distribution in the Solar System has nothing to do with the influx of meteors.  (OR do you mean meteorites????.... as in impacts????){see bottom paragraph}.

That being said, let's examine where most of the meteors
striking our atmosphere, 90% of them, come from....namely remains of comets in orbit around the sun causing the
major annual meteor showers during the year as we, the Earth, intercept those old orbits.  We have the Perseids, the Orionids, the Leonids, the Geminids, and the Eta Aquarids as the major annual showers, producing
anywhere from 20 - 200 meteors per hour on nights of maximum intensity.  Then we have a few minor showers worth watching, the Ursids, the Bootids, the Kappa Cygnids, and
the Lyrids, producing 2- 10 meteors per hour.  So how many of these are oriented to the ecliptic?  Only the Leonids, the Geminids, and the Eta Aquarids.  The rest come in from
non-ecliptic directions...Perseids from Perseus, Ursids
from Ursa Minor, Bootids from Bootes, Cygnids from Cygnus,
Orionids from Orion (-No, Orion is not on the ecliptic), and the Lyrids from Lyra.  We also know from past experience that new comets can appear from any direction at at any time, as most come in from the spherical Oort Cloud way out there, so no, meteors do not necessarily come into the equatorial region of the Earth.  Plus, we also have in our summer months, meteors that are called "sporadic" meteors, (meteors not associated with a particular comet or shower) generally 5-7 meteors per hour, and they also can come in from any direction at any time. Also, no known annual meteor shower member has ever struck the surface of the Earth, as being just comet dust. They have the consistancy of cigarette ash and are mainly grains of sand size striking the atmosphere at high altitudes (100 miles to 60 miles up)at very high speeds, averaging 40 miles per second. It's the sporadics that can, on occasion, strike the surface as meteorites.

(Meteorite information)
And if we examine past hits, we see that there is no
correlation to pattern of strikes on the Earth's surface.  The recent big ones have struck in Siberia (the Tunguska event June 30, 1908), Argentina, the Arizona desert (Meteor Crater in Arizona) and several small ones in Westersfield, Conn, the Alsace- Lorraine hit in France a few hundred years ago, and another I remember in Kansas.  Also the Sudbury, Canada hit that gave us all the world's supply of nickel (95% of it) many millions of years ago. Plus, scientists have recently found a bonanza of meteorites on, just laying on, the ice fields of Antarctica!
So I personally don't see any "equatorial or ecliptic" pattern. (In fact, it almost seems the opposite, a non-
favoring of the equatorial regions!)  Oh, another fine example of past hits is the Moon's surface....it's near the ecliptic too, but a simple examination of the lunar surface reveals that it's pock-marked all over it's surface, even at the poles. Same for the surface of Mars, and the moon's of the giant planets....there is no equatorial pattern on those bodies either....so I think I've presented enough information to dispel any thoughts about the equatorial plane, or the ecliptic plane, as being favored by incoming space debris.
Hope all this helps,
Clear Skies,
Tom Whiting
Erie, PA  USA