August 16, 2004 | David F. Coppedge

Earth’s Ugly Sister Can’t Get a Date

Venus is the subject of an interview with David Grinspoon of NASA’s Exobiology Research Program in Astrobiology Magazine, and admits that the entire surface of our hellishly hot sister planet looks young.  It appears the globe was resurfaced almost simultaneously in the relatively recent past. Grinspoon relives the surprises from the Magellan mission:

We’ve begun to understand the story of its surface evolution largely due to the Magellan mission in the 1990s.  The biggest surprise of Magellan was that the surface seems like it’s all the same age.  That’s what I’m calling the second great transition [the first being the loss of its water].  Something changed on Venus 600 or 700 million years ago to make the surface all the same age.
    If you use the word catastrophic it rubs some people the wrong way, but something dramatic happened on Venus which wiped out almost all signs of an older surface.  The planet got re-paved, basically, 600 or 700 million years ago.

Grinspoon discusses possible ways to explain such a “catastrophic” event on a planet similar in size to the Earth.  Did it start with water like Earth, then dry up?  Did the drying bring plate tectonics to a grinding halt?  Was the global volcanism a last belch of activity?  Or is the resurfacing periodic?  Nobody knows.  He talks about models he and other planetary scientists use to characterize what might have happened.  Putting dates to these models is imprecise, to say the least:

We’ve been taking a look at the models that have been done of the runaway greenhouse and the moist greenhouse to try to understand the time scale for the loss of the oceans.  The first thing you realize when you look at these models is that it has not been done in a very sophisticated way.  Not because the people that have done it are unsophisticated — Jim Kasting is the best in the business, and his models are state of the art.  But the state of the art is not that good.
    If you read Kasting’s paper, there are these huge uncertainties in the time scale.  He’s had to make many simplifying assumptions to try and solve the problem of the loss of oceans on a planet like Venus.  When you include all these assumptions, the real range of uncertainty in his model is longer than the age of the solar system.  In other words, Venus could have lost its oceans in 10 million years, or retained them for longer than the age of the solar system.  The time constraints are not that good.

Venus, it could be said, is trying out a lot of blind dates.

Whenever you listen to the just-so stories of the evolutionists (planetary or biological), always watch for the data.  Watch for something that was observed or measured in some way.  The radar scans from Magellan revealed a terrain remarkably uniform around the entire globe, with lava flows everywhere and few craters.  Its paucity of terrestrial diversity is very unlike the Earth, with its rich array of mountains, oceans, moving continents, rivers, weather systems, canyons and dynamic landscapes.
    On Venus, based on crater counts alone, the surface appears to be the same age, with nothing much having happened since some global resurfacing episode.  That is about all that can be said with any certainty.  Deducing what that age is from crater counts is a risky business based on assumptions of cratering rates which cannot be observed in the present.  The models and suggestions about water loss, early plate tectonics on Venus, periodic burps and so forth is just handwaving in the dark, assuming that the planet had a 4.5-billion year history.
    That number, the Sacred Parameter of Planetary Evolution, 4.5 billion years, is the assumed Age of the Solar System (acronym omitted for the sake of propriety).  What kind of a model has error bars as large as those he just admitted?  Is there any evidence for any of the model prior to the current observation of a uniformly cratered, resurfaced globe?  Is there any evidence of a missing 3.9 billion years?  No.  Science is supposed to be about what you can see, not what you can’t see.  When you need to visualize the unseen to keep your worldview from collapsing, it isn’t planetary science yet, just planetary mythmaking.

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Categories: Solar System

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