[meteorite-list] Fusion Crusted "Meteoroids"

From: Chris Peterson <clp_at_meteoritecentral.com>
Date: Wed, 25 Mar 2009 15:09:20 -0600
Message-ID: <F1C4AC51153F4D41AC8954FFF1389554_at_bellatrix>

>> There are not many potential crust forming bodies- a few dozen at most.
> TO ME A FEW SOUNDS LIKE A GUESS!

The number of Solar System bodies with atmospheres (which is what you need
in order for a grazing meteoroid to form a fusion crust) is well known- a
few planets and moons. This is not a guess.

> ARE YOU AWARE WE HAVE METEORITES THAT WE THINK MIGHT BE FROM PLANETS AS
> WELL. MAYBE WE WILL EVEN BE ABLE SOME DAY TO FIND THEN FROM OTHER PLANETS.
> DO YOU NOT AGREE WITH THE PLANETARY VARIETY?

These are a tiny fraction of all meteoritic material. When I talk about
meteoroids coming from two populations, that doesn't exclude a tiny
percentage of objects from other sources (maybe even interstellar). But
there's really very little doubt that the two populations I discussed
constitute the vast majority of meteoroids.

> IT IS A FACT THAT WE HAVE YET TO RECOGNIZE MATERIAL FROM COMETS ON EARTH
> BUT MANY PEOPLE SUSPECT THAT SOMEDAY WE WILL. OTHERS BELIEVE THAT CI1'S
> MAY BE COMETARY. AND THEY ARE VERY OLD INDEED AS OLD AS THE REST.

I'd be very surprised if some cometary material hasn't survived to the
ground. But the fact that we can't tie any material to known shower
fireballs (which vastly outnumber sporadic fireballs) just demonstrates my
point, that cometary material is very unlikely to survive an encounter with
the Earth's atmosphere.

>>IS THAT WHY WE GOT JUST HOURS NOTICE ABOUT A NEAR MISS JUST THE OTHER DAY?
>>IT SEEMS WE DON'T KNOW AS MUCH AS YOU THINK BASED ON TOO MANY NEAR MISSES.

We understand such bodies just fine. Obviously, we can't predict when any
particular one will pass near us until it has actually been observed. But we
do know a lot about the statistics of such bodies in general.

> GUESSING IS STILL GUESSING. GUESSES ARE PROVEN WRONG EVERY DAY. LOOK AT
> CARANCAS, THE DRY MOON, NOT. LOOK AT ALL OF THE MATERIAL THAT HAS HAD TO
> BE RE-CLASSIFIED. TOO MUCH GUESSING AND NOT ENOUGH GOOD SCIENCE.

What guesses? It sounds to me like you don't understand the difference
between a guess and a testable hypothesis. There's no need to guess about
how many bodies in space have fusion crusts- that is a figure that can be
reasonably estimated based on solid theory and observational evidence. When
early hypotheses are changed because of new evidence, that is a
demonstration of GOOD SCIENCE!

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message -----
From: <cdtucson at cox.net>
To: <meteorite-list at meteoritecentral.com>; "Chris Peterson"
<clp at alumni.caltech.edu>
Sent: Wednesday, March 25, 2009 2:39 PM
Subject: Re: [meteorite-list] Fusion Crusted "Meteoroids"


> CHRIS , WITH ALL DUE RESPECT HERE;
> ---- Chris Peterson <clp at alumni.caltech.edu> wrote:
>> There are not many potential crust forming bodies- a few dozen at most.
> TO ME A FEW SOUNDS LIKE A GUESS!
>> Neither is there a lot of meteoroid material whizzing around. Meteoroids
>> come from two populations: comets and the asteroid belt.
> ARE YOU AWARE WE HAVE METEORITES THAT WE THINK MIGHT BE FROM PLANETS AS
> WELL. MAYBE WE WILL EVEN BE ABLE SOME DAY TO FIND THEN FROM OTHER PLANETS.
> DO YOU NOT AGREE WITH THE PLANETARY VARIETY?
> Earth-crossing
>> cometary material is short lived, decaying into the Sun in just thousands
>> of
>> years (and in general, very little of this is likely to survive a grazing
>> encounter with the Earth).
> IT IS A FACT THAT WE HAVE YET TO RECOGNIZE MATERIAL FROM COMETS ON EARTH
> BUT MANY PEOPLE SUSPECT THAT SOMEDAY WE WILL. OTHERS BELIEVE THAT CI1'S
> MAY BE COMETARY. AND THEY ARE VERY OLD INDEED AS OLD AS THE REST.
> Material in the asteroid belt generally stays
>> there.
> TELL THAT TO THE DUDE THAT DUG METEOR CRATER.
> A tiny fraction is occasionally perturbed out and into an Earth
>> crossing orbit (or an orbit crossing another body with an atmosphere). IS
>> THAT WHY WE GOT JUST HOURS NOTICE ABOUT A NEAR MISS JUST THE OTHER DAY?
>> IT SEEMS WE DON'T KNOW AS MUCH AS YOU THINK BASED ON TOO MANY NEAR
>> MISSES. Any
>> such meteoroids will largely be in orbits without any long term
>> stability,
>> so again, they aren't likely to persist more than a few million years.
> IMAGINE WHAT YOU GET DONE IN A SINGLE DAY. NOW IMAGINE YOU HAD MILLIONS OF
> YEARS. A MILLION YEARS IS A HUGE AMOUNT OF TIME EVEN FOR GATHERING DUST,
> OOPS I MEAN CRUST.
>>
>> I disagree completely with your assessment that our scientific knowledge
>> about meteoroids and meteorites is based on guesses.
> I CERTAINLY DON'T MEAN ALL BUT A LOT IS STILL SOME.
> Understanding of
>> meteoroid dynamics and of meteorite formation and chemistry is solidly
>> based
>> on theory which is supported by a great deal of observational evidence.
>> There's really no "guessing" involved.
> GUESSING IS STILL GUESSING. GUESSES ARE PROVEN WRONG EVERY DAY. LOOK AT
> CARANCAS, THE DRY MOON, NOT. LOOK AT ALL OF THE MATERIAL THAT HAS HAD TO
> BE RE-CLASSIFIED. TOO MUCH GUESSING AND NOT ENOUGH GOOD SCIENCE.
> CARL
Received on Wed 25 Mar 2009 05:09:20 PM PDT