Author: Tim Thompson (timothy.j.thompson@jpl.nasa.gov) Title: Is Venus Young? Is Venus a +

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Author: Tim Thompson (timothy.j.thompson@jpl.nasa.gov)
 Title: Is Venus Young?
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   Is Venus a "young planet"? Could it be only a few thousand years
old, as opposed to the few billion that standard theories would imply?
I will look at Venus in what I consider the 3 major aspects of the
planet: its atmosphere, its surface, and its interior, in order to
explore the question of the age of Venus.

ATMOSPHERE

   Suppose that Venus were young, and very hot. One could explain the
very high temperature of the lower atmosphere of Venus as heat left
over from its recent creation, passing through the crust, and heating
the atmosphere. However, standard theory ascribes the high temperature
in the Venusian troposphere to a "greenhouse effect" caused by abundant
carbon dioxide (CO2). If one were to choose the heat-through-the-crust
option, then one must demonstrate that the greenhouse explanation is
either wrong, or inadequate. How might one do this?

   One hopeful argument, and the most common in the Velikovskian
community, is that such a greenhouse requires more water than is found
in the lower atmosphere of Venus. There has never been a quantitative 
demonstration of this claim, Though there are references to outdated
literature. So it has only the value of an assertion, until supported
by some calculational or observational evidence. However, on the side
of standard theory, we find in the abstract for Schofield & Taylor
(1982): "Only carbon dioxide, sulfuric acid, and water vapor are
considered as significant sources of opacity, and the role of the
latter component was found to be minor".

   While water vapor is not evidently needed to maintain a current
greenhouse effect in the Venusian atmosphere, there is reason to
believe that more water than seen now would be needed earlier, when
the "run-away" greenhouse was still "running away". observations of the
elevated D/H [*] ratio in the Venusian atmosphere imply that the
atmosphere of Venus once contained more water than it does now, but the
water was lost due to increasing heat through attendent, and definable,
escape mechanisms. This historical model of the Venusian atmosphere can
be found described, for instance, in Houghton (1979), Kahn (1982),
Prinn & Lewis (1984), and more recently in Donahue & Hodges (1992), or
Hunten (1993).

[*: D = Deuterium, H = Hydrogen. Deuterium is hydrogen with a deuteron
instead of a lone proton as an atomic nucleus. A deuteron is a proton
bound to a neutron. In common water, a known percentage of the hydrogen
atoms will in fact be Deuterium instead. Therefore, the ratio of D/H
in an atmosphere should be related to the mixing ratio of water in that
atmosphere. If the atmosphere is found to have an elevated D/H ratio
(in other words, too much Deuterium), the most likely explanation is that
hydrogen has been depeleted in proportion, due to the escape of water
from the atmosphere at an earlier time.]

   The clear point is that there is no reason to believe that a proper
greenhouse effect cannot be maintained by the current dry atmosphere of
Venus. There is clear observational evidence that the atmosphere once
had more water than it does now, and the means by which this water has
since escaped can be demonstrated quantitatively. There is no need to
invoke any non-greenhouse origin for the elevated tropospheric
temperature on Venus.

   Another argument seen is that the Pioneer Venus (PV) mission
measured the infrared (IR) flux from Venus, and found a large excess
emission, implying that the system was imbalanced strongly, and that
Venus was found to be much warmer than equilibrium with insolation
would presume. Any objective view of these observations, extensively
reviewed in Hunten et al. (1983), does not show any such an imbalance.
However, here on talk.origins, Ted Holden has expressed his own opinion
on the matter, in no uncertain words, on numerous occasions. For
instance ...

>>      From medved@access1.digex.net (Ted Holden)
>>      Newsgroups: talk.origins
>>      Subject: Venus:  Another piece of the big picture
>>      Date: 6 Aug 1994 22:52:47 -0400
[ ... ]
>>      I claim that empirical evidence involving Venus is being
>>      doctored and falsified at every turn because it does not fit
>>      with scientists' pre-conceived ideas involving the age of
>>      our solar system, and because it does not match any of the
>>      logical requirements of Carl Sagan's "super-greenhouse"
>>      theory.
[ ... ]
>>      Which is astonishing on the face of it, even aside from the
>>      clear statement by Taylor that the Pioneer Venus data is
>>      significantly more accurate than any prior measurement, and
>>      the clear implication that any and all past readings should
>>      simply be tossed.

   Mr Holden's opinion is entirely based on these two critical points.
The first point, that the data are being faked in order to avoid any
possible agreement with Mr. Holden's own pre-conceived notions, is
nothing more than a bald assertion. To ignore facts simply by claiming
that the opposition are deliberate liars is really the last refuge of a
scoundrel anyway, and I have no intention of addressing the matter,
other than to assert with equal conviction that this claim is blatantly
false.

   The second, and far sneakier point, almost seems to make sense, and
could easily trap the unwary. I will only mention in passing that if
Taylor [F.W. Taylor, in chap. 20, Hunten, et al. (1983)] really had
meant to imply that all data prior to PV should be "tossed out", then he
could easily have said so more directly, or in fact, since he was the
lead author of the paper in question, he could have simply done it. But
he didn't do it, nor did he say it, nor did he imply it. We don't need
Mr. Holden to tell us what Taylor "really" meant.

   Despite claims to the contrary, scientific data does not come with an
expiration date attached. I've never seen a laboratory notebook that
included a phrase like "these data not vaild after 5/5/2000". For
instance, in Hunten, et al. (1983), on page 30, in a chapter by V.I.
Moroz, there is a table of measured albedos that spans 1893-1968.
Mr. Holden roundly rejects the 19th century data as something that should
be tossed out on the grounds that it is too old. This is wrong. In 1893
they knew how to measure magnitudes, and they did a good job. While
current methods might produce higher precision, they are not likely to be
much more accurate. Since the data do not suffer from any identifiable
internal flaws, their cavalier dismissal is not acceptable, and would be 
questioned in any scientific venue. Mr. Holden claims that including
these brightness measures in the list of albedoes for Venus is improper.
I claim that it is not.

   However, the albedo is calculated from a more fundamental quantity,
namely the radiated energy flux. The entry probes from PV, which
dropped into the Venus atmosphere in 4 locations, reported excess IR
flux, over what was expected, once they had penetrated beneath the
clouds. This was pointed out in Hunten et al., (1983), by Taylor, and
others. However, as shown by Revercomb et al. (1982), Revercomb et al.
(1985), and Sromovsky et al. (1985),  these measurements were adversly
affected by design and engineering flaws, some of which could be
identified and corrected. The corrected fluxes did not show the
previously reported excess. Mr. Holden calls this "doctoring the data",
but any objective assessment can see what is really being done. Fixing
a mistake is not "doctoring data".

   A rigorous look at these PV data find them to be too affected by
noise, uncertainties in calibration, or systematic flaws, to make any
conclusion from them about net radiative balance. Indeed, it is not
even all that clear what really constitutes radiative balance. In Hunten
et al., (1983), Tomasko, in ch. 18, page 606, says that "If Venus is in 
equilibrium with absorbed sunlight, it should emit 150 +/- 45 W/m^2
corresponding to an effective temperature of 227 +15 -20 K.". 45 W/m^2 is
an uncertainty of 30%, which leaves a lot of room for the experimental
errors to fit a radiative balance, or a radiative imbalance. But, there
is another way to examine the question of radiative balance.

   The other way is to perform radiative transfer calculations on the
Venus model atmosphere(s), and determine, from our knowledge of the
atmosphere's constituents and structure, what its radiative
characteristics should be. There were other instruments on the PV
mission, besides radiometers, and they were used to characterize the
atmosphere of Venus with far more detail than could have been achieved
remotely. There have, in fact, been several studies along this line.
For instance, Schofield & Taylor (1982), Kamp et al. (1988), and Kamp
et al. (1990) have all demonstrated that the known physical structure
of the atmopshere is consistent with its known surface temperature, in
radiative balance with the sun, or at least nearly so. There is no
indication here of severe imbalance, nor of excess internal heat
expressed at the surface.

   One can also examine the question by an inverse process. If the
atmosphere of Venus really is being heated through the surface, it
should be convective. The Earth's atmosphere is heated in just this
way, by a surface heated via absorption of sunlight, and the Earth's
troposphere is dominated by convective transport. However, the
atmosphere of Venus is well known to have a sub-adiabatic temperature
profile in the troposphere, which means stability against convection.
this is not consistent with an atmosphere heated from below, as by a
hot surface, but it is consistent with an atmosphere that absorbs most
of the incoming radiation higher up, and this is consistent in turn
with the fact that only about 2% if solar radiation reaches the
surface of Venus.

   So we see that not only is there no positive evidence in favor of
the claim that the atmosphere is severely radiatively imbalanced, but
there is positive evidence that it is not. Of course, should Venus be
slightly out of balance, radiatively speaking, this would not be much
of a surprise. After all, the gas giant planets are known to radiate
considerably more energy than they receive from the sun, and even the
Earth itself is very slightly imbalanced on the warm side.

SURFACE

   The problem of energetic imbalance is not one likely to be expressed
only in the atmosphere. The energy required by the Velikovskian scenario
must come from within the planet. If we don't see it in the atmosphere,
perhaps we should look elsewhere, for the tell-tale signs of excess heat.

   This already creates a new problem, for, as Taylor himself pointed
out all the way back in Hunten et al. (1983), so much heat transported
through the crust should cause slumping in large topographic features.
PV, and prior Earth based radar measurements, were not consistent with
such an internal heat source. He also realized that to provide such heat
through volcanism was inconsistent with our knowledge of volcanism on
the Earth. This lead Taylor to openly reject the idea, long before
Mr. Holden had come up with it (Hunten et al. (1983), P. 658).

   More recent data supplied by the high-resolution radar on the
Magellan probe allows us to characterize the topography, and
volcanism on Venus with far better reliability than could be done a
decade ago. It is so obvious that the heat energy required to force
the desired imbalance cannot come through the crust by conduction,
that even Mr. Holden has evidently abandoned that line of argument,
in favor of ...

>>      That, of course (the little thing about "awesome" volcanic
>>      activity), is more or less what Magellan tells us.

   Volcanoes. If the heat can't get through the crust, maybe it can
bypass the crust by going through holes in it, i.e. volcanoes. Our
study of the atmosphere should already make one wary of such a claim.
After all, this much heat from volcano vents should affect the lapse
rate, and should be responsible for copious tropospheric convection,
neither of which is seen. So, we already have reason to be suspicious.

   Referring once again to Hunten et al. (1983), page 658, Mr. Holden
tells us that power amounting to 20% of the total solar input, or
about 1.5 x 10^15 Watts, needs to be emitted via the surface of Venus
to account for the perceived radiative imbalance. Thanks to James Acker,
of the Goddard Space Flight Center, we know that this requires a
minimum of about 157,000 Kilauea size volcanoes to be active at any
moment on the surface of Venus, with the added requirement that all of
the magma exuded therefrom must solidify in about 24 hours(!). This is an
outrageous requirement from any reasonable geophysical system. This is
what Taylor realized in 1983 when he rejected the idea to which Mr.
Holden still holds firm.

   So, are there enough volcanoes on Venus, really, to account for the
excess heat required by the Velikovskians, should they manage to get by
the atmospheric arguments? According to Mr. Holden, Magellan says yes.
According to Magellan, Magellan says no. For instance, Head et al. (1992)
mapped the volcano distribution over 90% of the Venus surface, using
Magellan data. They cataloged 1660 landforms and deposits, 550 shield
fields, 274 intermediate volcanoes, 156 large volcanoes, and 86 caldera
like structures. They also determined that an equilibrium re-surfacing
model would imply a volcanic flux of about 0.5 cubic kilometers per year,
which is comparable to the same activity on the Earth, about 0.3 to 0.5
cubic kilometers per year.

   See also Phillips & Hansen (1994), Crumpler et al. (1993), and Head et
al. (1991). Against these quantitative studies of volcanism, and the
observed surface distribution of volcanoes, all Mr. Holden can drum up
are vague and imprecise claims that there are "lots of volcanoes". This
is unconvincing.

   Another constant claim is that the Magellan images show a "fresh,
young" surface on Venus, and this supports the claim of "awesome"
volcanism. This claim, however, also does not stand up to examination.
Here, see for instance, Schaber et al. (1992). They mapped a database of
874 craters over 89% of the surface of Venus. The craters ranged from 1.5
to 280 kilometers in diameter, and are randomly distributed over the
surface. Of these, 62% are pristine, and only 4% are embayed by lava flows.
If Venus were subject to current "awesome" volcanism, or if it was even in
the fairly recent past, it is hard to explain why only 4% of its surface
craters would be embayed. See also Strom et al. (1994), and Bullock et al. 
(1993).

   Mr. Holden derisively complains about scientists and their "resurfacing
fairy", and insists that the obvious real explanation is a Velikovskian
young Venus. However, this is seen to be just another bald assertion,
once again unsupported by facts, or the reasonable interpretation of
facts. The studies cited here clearly explain the logic and methods
behind their determination of the age of the resurfaced areas, through
cratering statistics. Anyone in doubt can read and judge for themselves.

   In short, the surface features of Venus are all consistent with what
one would expect to see on an old Venus. The tell-tale signs of a young
Venus are not there. No help for the Velikovskian so far, but the worst
is yet to come.

INTERIOR

   The real tragedy of the Velikovskian scenario comes with the
interior of Venus. The interior of Venus, at least in composition,
is not unlike the interior of the Earth, which is basically true of
Mars and Mercury as well. All of the "terrestrial" planets are made up
of varying proportions of pretty much the same stuff, as extensive
observations would imply. The most powerful argument that can be raised
against the notion of a young Venus is that the current Venus is "Way
Cool", or, in other words, much too cold.

   Suppose Venus really were "young". Suppose it were molten only a
few thousand years ago. What would it look like now? Probably about
the same, molten. However, we know that Venus is not molten now,
because our landers, and Soviet landers, have landed on a solid surface. 
Furthermore, we know from the extensive topographic relief long since
verified by Earth- and spacecraft-based radar, that the crust of Venus
is thick. It must be, anywhere from 30 to 70 km thick (Baisukov et al.
(1992)), in order to support visible relief. Is it possible for Venus
to cool so much, so rapidly, between then and now?

   George R. Talbott thought so, and he even published a real
mathematical model to back up his claim (Talbott, 1978). However, his
model suffered from a serious attack of the blahs, as all he did was
use a simple Stefan-Boltzmann cooling algorithm, the same one you would
apply to a toy ball, and applied it to Venus. He even verified in the
laboratory that it was applicable to the toys. In order to apply this
toy equation to Venus, he invoked "forced convection" to rapidly move
magma from the interior to the surface, but then turned around and
calculated the cooling as if there were no thermal gradient at all
between the surface and the center. However, convection is caused by
thermal gradients, so these conditions are mutually exclusive and serve
to destroy the credibility of Talbott's model.

   Well, needless to say, this exercise of Talbott's, while perhaps
curious or interesting, was certainly not applicable to Venus, or any
other planet, nor for that matter to anything at all that is the size of
a planet.

   The business of analyzing planetary interiors is another of those
tasks, like radiative transfer in an atmosphere, in which great
strides have been made in relatively short time. New techniques, and
rapidly increasing computational ability have allowed the field to plow
forward. There have been numerous studies of the Venusian interior.
See, for instance,  Arkani-Hamed (1994), Phillips & Hansen (1994),
Arkani-Hamed et al. (1993), Janle et al. (1992), Basiukov et al. (1992),
Head (1990), and Marchenkov et al., (1990).

   The known physics of planetary interiors provides perhaps the
strongest argument of all against the idea of a young Venus. There is
simply no way to dump the excess heat so fast. The papers cited here,
and references therein, show how long the thermal time constants are
for such material, and expressly show how slow cooling really becomes
once a crust is formed. George Talbott's "forced convection" is a
fantasy, in view of the real viscosity of planetary material under the
physical conditions found inside Venus, or inside the Earth. There can
be no question but that Venus would be very much hotter than it is today,
if it were thousands of degrees hot only a few thousand years ago.

CONCLUSION

   I have covered what I thought were the big 3 topics here, but there
is one additional item that comes up from time to time, and that is the
question of the anamolous spin of Venus. While the planet does exhibit
a peculiar retrograde spin, this is also not something that can be
explained only by a recent catastrophic past encounter between Earth and
Venus. The details can be found, for instance, in McCue & Dormand (1993)
and Shen & Zhang (1988). The spin of Venus can be re-created by
gravitation over a long time span, or produced by catastrophic means
that involve known suspects (inner solar system asteroids), as opposed to 
planetary encounters.

   The conclusion, so far, is obvious. There are few, if any,
observational reasons for believing that Venus is a geologically, or
historically young planet. There are copious reasons, on the other hand,
for believing that it is not, and cannot be young.

REFERENCES:
[This list contains all papers referenced in the body of the message.
It may also contain papers not referenced above if I think they are
useful enough to include]

Arkani-Hamed, Jafar
"On the Thermal Evolution of Venus"
JOURNAL OF GEOPHYSICAL RESEARCH - PLANETS 99(E1): 2019-2033 (1994)

Arkani-Hamed, Jafar; G.G. Schaber & R.G. Strom
"Constraints on the Thermal Evolution of Venus Inferred from Magellan
Data"
JOURNAL OF GEOPHYSICAL RESEARCH - PLANETS 98(E3): 5309-5315 (1993)

Baisukov, V.L. et al., editors
"Venus Geology, Geochemistry, and Geophysics"
University of Arizona Press, 1992

Bullock, M.A.; D.H. Grinspoon & J.W. Head
"Venus Resurfacing Rates - Constraints Provided by 3-D Monte-Carlo
Simulations"
GEOPHYSICS RESEARCH LETTERS 29(19) 2147-2150 (1993)

Crumpler, L.S.; J.W. Head & J.C. Aubele
"Relation of Major Volcanic Center Concentration on Venus to Global
Tectonic Patterns"
SCIENCE 261(5121): 591-595 (1993)

Donahue, T.M. & R.R. Hodges
"Past and Present Water Budget of Venus"
JOURNAL OF GEOPHYSICAL RESEARCH - PLANETS 97(E4): 6083-6091 (1992)

Duncan, Martin J. & Thomas Quinn
"Long-Term Dynamical Evolution of the Solar System"
ANNUAL REVIEW OF ASTRONOMY AND ASTROPHYSICS 31(): 265-295 (1993)
[Not referenced above, but a very handy, and current review of our
knowledge and understanding of the evolution of planetary orbits in
the solar system - very useful demonstration that there is nothing
about the orbit of venus that is not perfectly in keeping with
standard interpretations]

Head, J.W.; L.S. Crumpler; J.C. Aubele; J.E. Guest & R.S. Saunders
"Venus Volcanism - Classification of Volcanic Features and
Structures, Associations, and Global Distribution from Magellan Data"
JOURNAL OF GEOPHYSICAL RESEARCH - PLANETS 97(E8): 13153-13197 (1992)

Head, J.W.; D.B. Campbell; C. Elachi; J.E. Guest & D.P. MacKenzie
"Venus Volcanism - Initial Analysis from Magellan Data"
SCIENCE 252(5003): 276-288 (1991)

Head, J.W.
"Processes of Crustal Formation and Evolution on Venus -
an Analysis of Topography, Hypsometry, and Crustal Thickness
Variations"
EARTH, MOON AND PLANETS 50-1(Jul-): 25-55 (1990)

Houghton, J.T.
"The Physics of Atmospheres"
Cambrodge University Press, 1979; 13 chapters, 203 pages,
ISBN 0-521-29656-0 [paperback] ... ISBN 0-521-21443-2 [hardback]

Hunten, D.M.
"Atmospheric Evolution of the Terrestrial Planets"
SCIENCE 259(5097): 915-920 (1993)

Hunten, D.M. et al.
"Venus"
University of Arizona Press, 1983; 30 chapters, 1143 pages,
ISBN 0-8165-0788-0

Janle, P.; A.T. Basilevsky; M.A. Kreslavsky & E.N. Slyuta
"Heat Loss and Tectonic Style of Venus"
EARTH, MOON AND PLANETS 58(1): 1-29 (1992)

JOURNAL OF GEOPHYSICAL RESEARCH - PLANETS
97(E8) -- 25 AUG 1992 Special Issue: Magellan at Venus
97(E10) - 25 OCT 1992 Special Issue: Magellan at Venus, Part 2
[Several of the papers cited herein are from these two special
issues. However, there are many more uncited papers that are
of value to anyone interested in the Venus question.]

Kahn, R.
"Deducing the Age of the Dense Venus Atmosphere"
ICARUS 49(1): 71-85 (1982)

Kamp, L.W.; F.W. Taylor & S.B. Calcutt
"Structure of Venus Atmosphere from Modeling of Night-Side
Infrared-Spectra"
NATURE 336(6197): 360-362 (1988)

Kamp, L.W. & F.W. Taylor
"Radiative-Transfer Models of the Night Side of Venus"
ICARUS 86(2): 510-529 (1990)

Luhmann, Janet G., et al., [editors]
"Venus and Mars: Atmospheres, Ionospheres, and Solar Wind
Interactions"
American Geophysical Union, Geophysical Monograph #66, 1992
ISBN 0-87590-032-1;  ISSN 0065-8448
[17 chapters, 430 pages; notable for chapter 2: "Chemistry of
Atmosphere-Surface Interactions on Venus and Mars", an
extensive review of the effect of the surface on the chemical
composition of the atmosphere]

McCue, J. & J.R. Dormand
"Evolution of the Spin of Venus"
EARTH, MOON AND PLANETS 63(3): 209-225 (1993)

Marchenkov, K.I. et al.
"The Stress State of Venusian Crust and Variations of its
Thickness - Implications for Tectonics and Geodynamics"
EARTH, MOON AND PLANETS 50-1(Jul-): 81-98 (1990)

Phillips, R.J. & V.L. Hansen
"Tectonic and Magmatic Evolution of Venus"
ANNUAL REVIEWS OF EARTH AND PLANETARY SCIENCE 22(): 597 (1994)

Prinn, R.G & Lewis, J.S.
"Planets and Their Atmospheres"
Academic Press, 1984; 5 chapters, 470 pages,
ISBN 0-12-446582-X [paperback] ... ISBN 0-12-446580-3 [hardback]

Revercomb, H.E. et al.
"Net Thermal Radiation from the Atmosphere of Venus"
ICARUS 61(3): 521-538 (1985)

Revercomb, H.E. et al.
"Reassessment of Net-Radiation Measurements of the Atmosphere of
Venus"
ICARUS 52(2): 279-300 (1982)

Schaber, G.G et al.
"Geology and Distribution of Impact Craters on Venus: What are They
Telling us?"
JOURNAL OF GEOPHYSICAL RESEARCH - PLANETS 97(E8): 13257-13301 (1992)

Schofield, J.T. & F.W. Taylor
"Net Global Thermal Emission from the Venusian Atmosphere"
ICARUS 52(2): 245-262 (1982)

Shen, M. & C.Z. Zhang
"Dynamical Evolution of the Rotation of Venus"
EARTH, MOON AND PLANETS 43(3): 275-287 (1988)

Sromovsky, L.A. et al.
"Temperature Structure in the Lower Atmosphere of Venus -
New Results Derived from Pioneer Venus Entry Probe Measurements"
ICARUS 62(3): 458-493 (1985)

Strom, R.G.; G.G. Schaber & D.D. Dawson
"The Global Resurfacing of Venus"
JOURNAL OF GEOPHYSICAL RESEARCH - PLANETS 99(E5): 10899-10926 (1994)

Talbott, George R.
"The Cabots, the Lowells, and the Temperature of Venus"
KRONOS IV(2): 3-25 (1978)
[Section III: "The Temperature History of a Large Mass
Initially at 1500 to 6000 Degrees Kelvin, Cooling by Radiation
into a 200 Degree Kelvin Sink, Covering 3500 Years"; pages 11-25]