Re: Venus's atmosphere/afterthought

[Brian Whatcott <betwys1@SBCGLOBAL.NET>]

I enquired of Dave Williams, about the refraction experiments
near Venus. He showed me that I was the willing victim of the displaced
zero in a graph, and not the first one, I expect.

Accordingly, I concur that the available data does indeed
support a value of 90+ bar for the surface pressure there

Brian.

-----Original Message-----
From: Dave Williams [mailto:dwilliam@nssdc.gsfc.nasa.gov]
Sent: Tuesday, July 29, 2003 9:21 AM
To: brian.whatcott@k....
Subject: Re: Goddard vs. JPL?

        Brian,
The graph at:

http://www.ebicom.net/~rsf1/vel/1918vpt.htm

cuts off at 30 km altitude where the pressure is about 9 bars.
 Continuing down to the surface gives about 91 bars.
        Dave

David,

This URL for which you are listed as a contact, gives Venus surface
pressure around 91 bars.

<http://nssdc.gsfc.nasa.gov/planetary/factsheet/planet_table_british.html>
But this URL has a table which seems to show a surface pressure around 9
bars for
Venus atmosphere. This was deduced from grazing refraction experiments.

<<http://www.ebicom.net/~rsf1/vel/1918vpt.htm>http://www.ebicom.net/~rsf1/vel/1918vpt.htm>
Can you say which is likely to be closer to the mark?

Brian whatcott



At 03:12 PM 7/24/2003 -0700, you wrote:
> Another interesting aspect of Venus's atmosphere:
>
> From:
> <http://hyperphysics.phy-astr.gsu.edu/hbase/solar/venusenv.html>
>
> "The mass of the Venus atmosphere is about 90 times that of the Earth's
> atmosphere. 90% of the Earth's atmosphere is within 10 km of the surface,
> whereas you have to go to 50 km to capture 90% of the atmosphere of Venus."
>
> From:
> <http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html>
> "Venus Atmosphere
> Surface pressure: 92 bars
> Surface density: ~65. kg/m3
> Scale height: 15.9 km
> Total mass of atmosphere:  ~4.8 x 1020 kg"
>
> From: <http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html>
> By comparison, for earth:
> "Terrestrial Atmosphere
> Surface pressure: 1014 mb
> Surface density: 1.217 kg/m3
> Scale height: 8.5 km
> Total mass of atmosphere:  5.1 x 1018 kg"
>
> Larry Woolf
> General Atomics
> 3550 General Atomics Court
> Mail Stop 78-110
> San Diego CA 92121
> Ph:858-526-8575
> FAX:858-526-8568
> http://www.ga.com
> http://www.sci-ed-ga.org
>
> > -----Original Message-----
> > From: Frank Cardulla
> > Sent: Wednesday, July 23, 2003 8:07 AM
> > Subject: Venus's atmosphere
> >
> > Why is it that Venus has been able to retain an atmosphere that exerts a
> > pressure about 90x that of the atmosphere on Earth?  The mass of
> > Venus is less
> > than that of Earth, so its gravitational acceleration is only 8.9
> > m/s2.  Its
> > atmosphere is hotter (about 737K vs. 288K).  Even though its
> > atmosphere is mostly
> > CO2, with a molar mass of 44 compared to an average of about 29
> > for Earth's
> > atmosphere, it seems counterintuitive that it could retain such a dense
> > atmosphere compared to Earth.


Brian Whatcott    Altus OK    Eureka!