When Venus started out, it very likely was like Earth and very likely did have plate tectonics. On Earth, when surface gets subducted, the volatiles are recycled as gases to the atmosphere by volcanoes that surround the subduction zones.

In silicate melts, water acts as a diluent and lowers the viscosity. Water also acts to increase the density of a silicate melt. I think this increase in density is what drove all of the water on Venus into the mantle. As sediments are subducted, silicate melt with the highest density will move down. If that silicate melt has water in it, the water is moved to the mantle and lost.

On Earth, there was life early on, so the subducted sediments also contained free carbon. At high temperatures, water and carbon form methane, which is a gas and which will phase separate from silicate melts and move up as bubbles. I think it is the presence of carbon in Earth sediments which prevented the loss of hydrogen to the mantle.

The conventional thinking is that Earth’s atmosphere became oxic due to the loss of hydrogen into space. I think that is not correct. I suspect that as photosynthesis generated O2, it also generated carbon and also formed the large banded iron formations of Fe2O3 as soluble ferrous iron was oxidized to insoluble ferric iron. I suspect that when the carbon and Fe2O3 were subducted, the Fe2O3 was reduced to liquid metallic iron. Liquid metallic iron would separate out as a separate phase from silicate melts, and being much denser would migrate down. The gas generated (carbon monoxide) would migrate up, recycling the C and O to the atmosphere while the reducing equivalents of that carbon were carried down by the liquid iron.

If this idea is correct, then a possible way to terraform Venus would be to take surface iron oxides, make metallic iron, releasing O2, dissolve carbon in that metallic iron and inject that metallic iron at hot spots like this volcano. As the liquid iron moved down, and encountered water containing silicates, methane would form and move the hydrogen up to the surface. Once there is enough water in the atmosphere, CO2 starts coming out as carbonates.

You would probably want to specifically start up plate tectonics by injecting water (or carbon containing iron) at specific places. Water in the magma would greatly reduce viscosity and facilitate convective flow.

“29th Contact, July 7, 1975″
Ever heard about post-dating?

11 april 2010 I can wrote on computer about crash in Smolensk, date it “8 april 2010″, publish it today and bask in glory of clairvoyancy. So only proof is date of publication.

But all of it is moot, because Venus was explored significantly earlier.
http://en.wikipedia.org/wiki/Venus#Exploration
“Mariner 2 mission… on December 14, 1962… passing 34,833 km above the surface of Venus. Its microwave and infrared radiometers revealed that while Venus’s cloud tops were cool, the surface was extremely hot—at least 425 °C”

http://en.wikipedia.org/wiki/Observations_and_explorations_of_Venus#Flybys
“# In 1967, Venera 4 became the first probe to send data from within Venus’s atmosphere. At about the same time, Mariner 5 measured the strength of Venus’s magnetic field.
# In 1974, Mariner 10 swung by Venus on its way to Mercury and took ultraviolet photographs of the clouds, revealing the extraordinarily high wind speed in the Venusian atmosphere.”

Last but not least: some of things that you cited was NOT corroborated. For example point 117 (“But completely other forms (of life) do exist”? Yeah, riiight).

So, Michael Horn, you wrote entirely BS.

I’m very open to being completely wrong on that.

Not just atmospheric makeup, but also density. Venus’ atmosphere is ~100 times thicker than Earth’s.

We really need Piers Anthonys MacroScope.

Gary 7

The pressure at the surface of Venus is about 90 times that at the Earth’s surface. Venus has enormous winds that cause gas to rise and fall in altitude. As the gas changes height, the pressure changes, and the gas expands or is compressed. When a gas is compressed, its temperature increases. This creates a massive temperature difference between the top of the atmosphere and the surface.

Venus is closer to the sun, but reflects more light, so absorbs slightly less energy than the Earth. The visible surface is the top of the clouds, which approach radiative balance between the incoming solar radiation and the outgoing longwave radiation to space, are relatively cool. The temperature at an altitude where pressure is about 1 Earth atmosphere is actually remarkably Earth-like. But the clouds are about 50-80km above the surface, and compression warms the gas at about 8C/km of altitude (the ‘adiabatic lapse rate’) so the surface is about 400-640C hotter.

The references to a “runaway greenhouse effect” are actually to Venus’s ancient history. It is believed that several billion years ago Venus was like Earth, with a thin atmosphere and oceans on the surface. But somehow all the water disappeared, the carbon locked up in water-related carbonates was released again, and turned Venus into what we see now. This process is thought to be the “runaway greenhouse” – basically, the oceans boiled.

The present day temperature on Venus is easy to explain, and has relatively little to do with CO2 being a greenhouse gas. It’s simply that Venus has a much thicker atmosphere, and high level near-opaque clouds.

Gary 7

“She’s 30% closer to the sun that we are and you think she’s warmer because of CO2?

You have lost it completely.”

You can’t be serious, surely? If you think that distance to the Sun is the sole contributing factor to a planet’s surface temperature, then ask yourself why Mercury is cooler than Venus, despite being almost twice as close to the Sun as Venus is on average. Could it be the CO2 atmosphere of Venus, or am I losing it?!

Long before we are ABLE to terraform a planet, we’ll have decided it’s superfluous.

Far easier to just BUILD what we want in space, wherever we want them.

Long live Freeman Dyson,,,

Gary 7

Anyway, the thing that I remember most about Venus comes from the Soviet Venera missions. It’s hard to get a sense of the heat and density of the atmosphere at the surface of Venus until you read about these missions. Can you imagine jettisoning your parachute 50 km above the Earth’s surface and still have a soft landing?

FWIW, “Idunn” is the name of a Norse goddess.

& 33. jearley too: Thanks.

Even if it does spoil my joke when you know the correct pronunciation.

Alas, every single other evening for the last 2-3 weeks has been too cloudy to see anything, and I didn’t have my telescope or camera with me at Target.

Here’s to sharing knowledge!

J.

Yes, and it should be about 30% warmer than earth, in other words, 30% of the temp diff between zero Kelvins and OUR average temp due to solar heating alone of 273 Kelvins(zero degrees C). So W/O an atmosphere, Venus should average about 354 Kelvins (81 degrees C), not 723 Kelvins (450 degrees C).

I think however, your estimate of 30 % is a bit low. Should be closer to 37%. Adjust figures accordingly.

Gary 7

Light’s intensity falls off with the square of the distance. Using 0C or 273K as the average temperature of the Earth, we multiply that by the square of the distance from Earth to the Sun, about 150 million kilometres, and divide by the square of the distance from Venus to the Sun, about 110 million KM.

This back-of-the-envelope calculation suggests Earth would be around 527K, or 254C, if it were in Venus’ orbit. Since Venus proper is about 490C or 763K, it’s about 200 degrees hotter than we’d expect from solar heating. That dense CO2 atmosphere might be contributing something….

You seem a little rusty in your Science knowledge, since the above is usually taught in High School. It might be time for a refresher course.

HJ Hornbeck