[meteorite-list] Recognizing a Venusian meteorite

From: E.J <jonee_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:35 2004
Message-ID: <3F986C52.5000704_at_epix.net>

Howard Wu wrote:

> Still the question was how would we recognize a venusian meteorite?

Great question to ponder.

As a "lay" astrogeologist here is "an" answer as I see it. So far we
only have the direct sampling of the Venusian atmosphere by the Soviet
mission. The isotope ratios of the Venusian atmosphere will help in
confirming meteorites from the Mercury Venus Zone. The analysis will
initially lie in the differences in isotopic ratios between Mars and
Venus, I feel. Age of formation will be equally important. We need a
mission to Venus again!

We know that there is a gradient of " heavy to light" elements produced
by a presolar shockwave(s) that swept elements outward from the center.
This is why the inner planets are stony-irons and the outer ones are
gaseous. Having higher "momentum / inertia"moments, the heavier
elements tended to remain in the inner solar system while lighter
elements rode the bow wave to the outer edges. Of course all the atoms
of each element were not completely segregated, none-the -less there was
a measurable sorting. We know this from measuring values against the
elemental abundance of the solar system. The"elemental abundance" is a
calculation of all elements against each other such that we know the
ratio of each individual element to all the others or, in another way,
we know their individual percentage in the entire mass of the soar system.

Along with the afore mentioned distribution/concentration of elements,
is a subset distribution within the isotopes of individual elements.
For example, from each area of concentration in the solar system for
oxygen, the ratio of isotopes such as Oxygen 16, 17, and 18 as they
relate to each other vary. Specifically, they vary with the distance
they are from the center of the solar system. The lighter the isotope,
the more distantly it moved toward the outer edge of the solar system.
The Earth Moon ratio has been determined. This is one of the means we
used to identify lunar meteorites. Similar ratios were used to identify
Martian meteorites based on Viking Lander measurements.

Igneous rocks from Earth and Mars pretty much contain the same minerals
so we rely on isotopic ratios and radioisotope ages to shore up our
findings. In like manner, that is how the determination of a Veneusian
meteorite will happen. While the jurry is out on Mercury, some think it
was captured and its orbit of formation lies elsewhere, (isotopic ratios
may not be what is expected from a planetoid forming close to the solar
center), Venus is another story. It is certianly a differenteated body
and recently volcanicaly active. Any Enstatite chondrite (E,EH,EL)
can't be from Mercury nor Venus. Likewise the age of
formation/crystallization for Venuisan material will likely be much less
younger than asteroidal material.

So Venusian material will likely be isotopically weighted toward Oxygen
18 and will have a crystallization age closer to Martian material but I
am guessing under 2 but less than 3-3.5 billion years.


Regards,
Elton
Received on Thu 23 Oct 2003 08:03:30 PM PDT