Venus Express press conference November 28th, Venus: a more Earth-like planetary neighbour Options

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Venus Express press conference set for November 28th.

http://www.esa.int/esaCP/SEMX1C63R8F_index_0.html

‘Venus: a more Earth-like planetary neighbour’
Latest results from Venus Express
28 November 2007, 15:00, room 137
ESA Headquarters, 8-10 rue Mario-Nikis, Paris

15:00 Introduction, by Håkan Svedhem, ESA Venus Express Project Scientist
15:07 Venus: What we knew before, by Fred Taylor, Venus Express Interdisciplinary Scientist

15:15 Temperatures in the atmosphere of Venus, by Jean-Loup Bertaux, SPICAV Principal Investigator

15:25 The dynamic atmosphere of Venus, by Giuseppe Piccioni, VIRTIS Principal Investigator

15:40 Venus’s atmosphere and the solar wind, by Stas Barabash, ASPERA Principal Investigator

15:50 Climate and evolution, by David Grinspoon, Venus Express Interdisciplinary Scientist

16:00 Conclusion, by Dmitri Titov, Venus Express Science Coordinator and VMC scientist

16:05 Questions and Answers

16:25 Individual interviews

17:30 End of event

Craig

[Julius]

I am no planetary sceintist but just a humble enthusiast!I have a few queries maybe some of you could answer:

Why should Venus have a thicker atmosphere than Earth provided it lacks a magnetic field and hence being in direct contact with the solar wind ,which should produce higher rates of atmospheric loss.This seems to be the explanation for mars!?

The moon is said to be acting as a friction brake on Earths rotation and thus is slowing it down.Has anyone explained clearly why Venus is such a slow rotator in the absence of a moon!Could a previous collision of a cosmic body with Venus help to explain this . Venus was once(i think its about 500-800 million years ago) entirely resurfaced by hot magma .Could this have happened when this theorised collision took place?

Why should Venus lack a magnetic field given its the same radius and almost same density like Earth?Could it be that its dry compared to Earth ,simply explain for this significant difference?

[JRehling]

I am no planetary sceintist but just a humble enthusiast!I have a few queries maybe some of you could answer:

Why should Venus have a thicker atmosphere than Earth provided it lacks a magnetic field and hence being in direct contact with the solar wind ,which should produce higher rates of atmospheric loss.This seems to be the explanation for mars!?

The moon is said to be acting as a friction brake on Earths rotation and thus is slowing it down.Has anyone explained clearly why Venus is such a slow rotator in the absence of a moon!Could a previous collision of a cosmic body with Venus help to explain this . Venus was once(i think its about 500-800 million years ago) entirely resurfaced by hot magma .Could this have happened when this theorised collision took place?

Why should Venus lack a magnetic field given its the same radius and almost same density like Earth?Could it be that its dry compared to Earth ,simply explain for this significant difference?

That last question is a good one, and there is a lot of mystery still remaining. In my mind, sort of a chicken-egg problem:

Assuming Venus were initially proto-earthlike, but had lost most of its water, that would prevent CO2 from becoming locked up in carbonates (Earth and Venus actually have similar reservoirs of the C and the O, but on Earth it's tied up in rocks). That would give Venus the huge partial pressure of CO2 that creates the high temperatures, and the solar tides that can actually slow the planet's rotation. And presumably, a slower rotation could be a factor in the lack of a magnetic field. But why would Venus lose its water in the first place? If it initially lacked a magnetic field, then that allows solar wind to hit the upper atmosphere, which would speed the loss of H2O. And if it were initially hot, then that pushes more of the H2O into higher altitudes, also speeding the loss of CO2. But it's not clear how this process, with several self-reinforcing factors creating the modern Venus, was bootstrapped. Maybe Venus started without a magnetic field for some unknown reason. Maybe it started off with very slow rotation as a consequence of its accretion.

The solar wind does not remove a lot of CO2, however, because it's a heavy molecule and hard to break apart. H2O is easier to break apart, and when it does, the H escapes. Even if you broke CO2 apart, the C and O would still be apt to stay around, being heavier. Mars has a lower escape velocity, so it can lose nitrogen and CO2 at a non-negligible rate.

It is unlikely that a massive collision caused Venus's global resurfacing. We can see lots of worlds that bear the scars of past collisions, and they don't cover their tracks -- they leave big rimmed basins. I guess it's hard to falsify whether or not a modest collision could have been the trigger starting the process. But there are models to explain the resurfacing event, too. Basically, that Venus boils off its inner heat in a few, rare planetwide meltdowns, instead of letting a little out all the time like Earth.

While the right collision (or stage in the accretion, taking the form of one big lump coming in fast) might have played around with Venus's rotation, it is not a necessary or sufficient explanation. Venus's axis is very nearly aligned with its orbit, which would be unlikely to happen if a big random torque were applied. Dynamical models of tides raised in Venus's atmosphere by the solar heating on the dayside predict that the current rotation is one of two stable states. It must have taken a long time for this to halt the rotation if it were initially fast, but it may not have been fast. A collision/accretion event may have done part of the job, with solar tides doing the rest.