date:20100425

Re: [meteorite-list] Venus Catastrophic Resurfacing HypothesisChallenged

2010-04-25 Thread Sterling K. Webb

Listoids and Venus Fans,

The Global Catastrophe "Hypothesis" became a problem
as soon as the Magellan dataset was mostly complete. The
data was turned over to the "crater-counters" who are able
to date a planetary surface by the statistical distribution of
crater size, and date it quite precisely, too.

When they announced the age of the Venusian surface
as 520 million years, plus or minus a 40-50 million year
error (or 480 to 560 my), they were immediately surrounded
by hysterical geologists screaming that they had to be wrong.

The crater counters were replaced by other crater counters
who gave the same results. This is a narrow specialization --
crater counting -- there are only so many crater counters,

and it's a very precise technique that has dated every solid
planetary surface we can image with results that are both
consistent and to every appearance accurate everywhere.

A decade or so was wasted on "geological" mechanisms
that could re-surface without outside interference. They
were largely hooey that convinced no one, posing improbable
mechanisms to accomplish world-wide simultaneous subduction.
The problem is not a "hypothesis" problem; it is a "fact" problem
looking for a hypothesis.

If we take a step backward and look at events in the
ENTIRE solar system, we see that:

a) ~600 million years ago, the largest asteroid breakup
in the last 4 billion years occurred (the Flora Family),

b) starting at 600 million years ago, the impact rate in
the solar system jumped up to high levels not seen
for 3.2 billion years (dated by lunar impact spherules
collected by the Apollo missions),

c) between 600 million years ago and 500 million years
ago, the Earth had three catastrophically nasty ice ages,
including the Snowball Earth episode in which the entire
planet froze to the equator, the worst ice age ever,

d) 484 million years ago, the Earth suffered a prolonged
period in which the rate of meteoritic infall was up to 150
times greater than it is today,
http://www.psrd.hawaii.edu/Mar04/fossilMeteorites.html
and

e) the surface of Venus was wholly or partially melted and
resurfaced with fresh rock (just like the old days, huh?).

I see these events as connected, as I've been sometimes
posting here for the last 6 or 7 years. Or, they could be one
freakin' big coincidence...

So, I read the RTT paper with great interest. They advance
solid arguments for the conclusion that the RTT had to be
formed in one discrete episode or interval. In a word, that
it's datable. They then assert that it had to have formed very
early in the planet's history because "thermal modeling
indicates that ribbon fabric formation requires an extremely
high thermal gradient..." That is, a high internal heat flowing
up to the crust as it does at the end of planetary formation
and cooling. In other words, you can't form RTT unless the
crust is very hot. That is the extent of their "dating" attempt.

The ancient origin would be true in the case of the absence
of a viable geological "catastrophic" or global turnover model
ONLY IF you exclude impacts (giant or multiple) large enough
to melt the crust down to the mantle. Best way to prove your
case is to ignore anything that would disprove your case,
I always say.

The RTT are scattered in disconnected patches over the
planet. They could be a relict of ancient terrains or they
could be the places where the 100-300-kilometer asteroids
DIDN'T fall. The fall of planetoid sized bodies, of course,
heats the crust planet wide by degrading the impact energy
into thermal energy. The heat doesn't have to be internal
when you melt a planet's surface.

Hansen and Lopez have another paper on the RTT,
characterizing them as lava "scrum ponds," also from
this same year (2009):
http://www.lpi.usra.edu/meetings/venus2009/pdf/2012.pdf
(I think you ought to hold it down to one theory a year.)

This is a strange idea since the RTT is 1-3 km. HIGHER than
the low flat plains -- why didn't the lava run off? But, then,
I'm no geologist and I don't really know how to make lava
run uphill... How you do dat? In fairness, a few RTT parches
are on the lowest level... but only a few small ones.

Another view on the RTT by another member of the
original Magellan team (this one from 1996):
http://www.agu.org/pubs/crossref/1996/96JE01245.shtml
Author of many papers on Venus; Google "Ivanov Venus."

There's another theory of the RTT, the "pulsating
continent" theory. Bouncy continents... That sounds
like fun:
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V61-4TRR8Y0-1&_user=10&_coverDate=11%2F30%2F2008&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1310409062&_rerunOrigin=google&_acct=C50221&_version=1&_urlVersion=0&_userid=10&md5=1a74f8614c1c46478bfbfe77b807a05a

There seems to be this continuing effort in explaining
Venus' geology by "mechanisms without outside interference."
I'm tempted to see it as the old "we're-geologists---take-your

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