[meteorite-list] fukang (the neverending thread)/what countryisthe hardes...

From: MexicoDoug_at_aol.com <MexicoDoug_at_meteoritecentral.com>
Date: Fri Jan 6 14:04:39 2006
Message-ID: <28f.391ac08.30f0193d_at_aol.com>

Hi Marcin and Matteo - Tropical refers to latitude, and humidity refers to
weather. They are independent. 0 humidity exists only in outer space...or on
the Moon, etc...even the driest deserts are in the 10% relative humidity
range.

BUT! Air doesn't get more than about 4% absolute humidity anywhere, I
recall. That's the most vapor than can actually be put into the air
percentage-wise. So, in a sweltering hot place, with a disturbing 62% RELATIVE humidity,
there is less than 2.5% absolute humidity, but if you cool it down it rains.
So in the tropics you get lots of rain in the late afternoon - and rapid
fluctuation in temperature cause condensation and precipitations. Matteo didn't
say relative humidity so if we willingly generously gave him the benefit of
the doubt, we can assume he meant absolute or specific humidity. Venice may
be all wet, but so it Antarctica, in a sense.
 
Arizona is does have higher temperatures, but it is not any more tropical
that the frequently brutal temperatures of Death Valley, California (which does
team with life)... and the driest places on Earth include the polar desert
"Valley of the Dead" (Taylor Valley) of Antarctica and the Gobi desert, the
later having average temperatures below zero! One factor additionally to
consider in a desert is the radiative effect for an iron meteorite being baked in
the sun with a dark magnetite layer ... it gets hot, and so does the air
immediately around it!
 
When we heat things up to dry them out...it is not principally the "heat"
doing the drying on the object. It is the elevated temperature of the air
around the object sucking the water out of the object because of the equilibrium
being pushed increase the total amount of water the air holds, and the air
"attracts" the water just like a vacuum would...
 
Add to that, rusting happens what, twice as fast for every 10 degrees C
increase in temperature?...and it is easier to relate to the comments on some of
the stability of Russian irons...

Relative humidity is not easily comparable from one location to another
without considering the temperature. You compare them in a Mollier Diagram and
answer almost any humidity-saturation-water concentration question looking at
one. The warm the ambient temperature, the more water vapor that the air
holds until it gets saturated. 30% relative humidity IS less water in a colder
place than a warmer place that has the same 30% relative humidity.

Does this make sense? Part is intuition but part is somewhat
counterintuitive...but to understand the crux of what happens to preserve meteorites
exposed to the air or even soil, these processes are the ones to mull for the
environments.

Saludos, Doug


1/6/2006 9:20:33 A.M. CST Matteo writes:

>not sure from me....a person live in Arizona have a "
>little " difference on humidity from one live in
>Venice....

Matteo


1/6/2006 7:56:57 A.M. CST, Marcin writes:

> Right, I have many pieces of Seymchan and never seen a
> trace of rust. And Russia is not a tropical land where
> the umidity its near the 0. The same for Esquel and
> Imilac, super stable pallasite.
> Matteo

Matteo, how in Tropical climate humidity can be 0 ?
 
Received on Fri 06 Jan 2006 02:04:29 PM PST