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[student] magnetic field on venus



 
 
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  #1  
Old March 2nd 05, 07:39 AM
Adam
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Default [student] magnetic field on venus

Hi,

If our magnetic field protects our atmosphere from being blown away by
solar winds then how come venus can maintain an atmosphere 90x the
pressure of ours without a magnetic field?

I thought gravity except Venus is less dense and smaller than Earth so
I guess thats ruled out.

Can someone help? or point me in the right direction?

Thanks in advance,
Adam.
  #2  
Old March 2nd 05, 10:48 PM
Stuart
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Adam wrote:
Hi,

If our magnetic field protects our atmosphere from being blown away

by
solar winds then how come venus can maintain an atmosphere 90x the
pressure of ours without a magnetic field?


Good question.

I thought gravity except Venus is less dense and smaller than Earth

so
I guess thats ruled out.


As you know, magnetic field is not the only thing that helps Earth hang
on to its atmosphere. There is much talk of this as of late because it
appears Mars once had an atmosphere thick enough to allow for liquid
water on its surface.

Can someone help? or point me in the right direction?


As stated above, Venus has a really thick atmoshpere, in other words,
there's an awful lot of atmosphere to ablate. It is also mostly CO2, a
heavy gas thats hard to get rid of. Its gravity is ~.86 that of Earth's
gravity, and more than twice that of Mars.

Stuart

  #3  
Old March 2nd 05, 11:00 PM
Robert Grumbine
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In article ,
Adam wrote:
Hi,

If our magnetic field protects our atmosphere from being blown away by
solar winds then how come venus can maintain an atmosphere 90x the
pressure of ours without a magnetic field?


Um, that'd be because you started with an incorrect premise.

The earth's magnetic field is not needed to retain its atmosphere.
It is useful, though, for keeping high energy particles from the
sun away from us at the surface.

I thought gravity except Venus is less dense and smaller than Earth so
I guess thats ruled out.

Can someone help? or point me in the right direction?


The thing you want to look up is gaseous escape from planetary
atmospheres. Most standard introductory astronomy books will
have a section on it. The main balance is between the temperature
of the gas, the molecular weight, and the escape velocity.

While Venus is slightly smaller than the earth, it's only slight.
It's hotter, so the molecules are moving faster. But the main
gas involved in Venus's atmosphere -- CO2 -- is sufficiently heavy
that there's no way any appreciable amount will be lost. What Venus
can't retain (neither can the earth) are hydrogen and helium. It's
too hot and small, as is the earth.

--
Robert Grumbine http://www.radix.net/~bobg/ Science faqs and amateur activities notes and links.
Sagredo (Galileo Galilei) "You present these recondite matters with too much
evidence and ease; this great facility makes them less appreciated than they
would be had they been presented in a more abstruse manner." Two New Sciences
  #4  
Old March 7th 05, 08:32 PM
Sander Vesik
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Default

In sci.space.science Adam wrote:
Hi,

If our magnetic field protects our atmosphere from being blown away by
solar winds then how come venus can maintain an atmosphere 90x the
pressure of ours without a magnetic field?

I thought gravity except Venus is less dense and smaller than Earth so
I guess thats ruled out.

Can someone help? or point me in the right direction?


Wouldn't the obvious conclusion be that protecting the atmosphere
from being "blown away" was not one of teh functions of the magnetic
field?


Thanks in advance,
Adam.


--
Sander

+++ Out of cheese error +++
 




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