Manned Venus Mission?

On Tue, 16 Oct 2018 10:28:00 -0000 (UTC)
Mike Collins wrote:


Its a pity Brad Guths no longer here to read this.

https://www.businessinsider.com/nasa...share=1a1c01de


! The current climatic conditions and composition of the atmosphere are
! the result of a runaway greenhouse effect (an extreme greenhouse
! effect that cannot be reversed), which transformed the planet from a
! hospitable Earth-like "twin" world in its early history.

This comes from a speculative paper by Carl Sagan written around 1970.
I remember reading it in the UCLA library many years ago. Something
about the paper bothered me, and I puzzled over it for an hour or so.
Then I realized the problem. The paper assumes planets were created
in their present form. But science tells us that the early earth
atmosphere was more like that of Venus and Mars: high carbon dioxide
concentrations and no free oxygen. It was the evolution of life that
created breathable air.

Many papers contain speculation about the early atmosphere on earth, but
rather than assuming it was created in its present form, it is far more
reasonable to assume that all the planets originally had
similar atmospheres: hydrogen, helium, carbon dioxide, ammonia,
methane, water. Depending on the planet's gravity and distance from
the sun, the lighter gasses tended to boil away. On Venus the
hydrogen (molecular weight 2), helium (molecular weight 4), methane
(molecular weight 16), ammonia (molecular weight 17) and water
(molecular weight 18) have all boiled away precluding the creation of
earth-like life. Carbon dioxide (molecular weight 44) remains. The
intense heat on the surface of venus is caused more by the strong
atmospheric pressure than any greenhouse effect. As noted in the paper:

! As surprising as it may seem, the upper atmosphere of Venus is
! the most Earth-like location in the solar system. Between
! altitudes of 50km and 60km, the pressure and temperature can
! be compared to regions of the Earth's lower atmosphere. The
! atmospheric pressure in the Venusian atmosphere at 55km is about
! half that of the pressure at sea level on Earth.

Our earth is heavier than Venus and has stronger gravity. It is also
farther from the sun. So enough water, ammonia, and methane were
left for our planet to develop life.

Mars is cooler, but has much weaker gravity. As with Venus, water,
methane and ammonia were lost, and carbon dioxide is what remains.
If life began there, it didn't last long.

Carl Sagan was apparently a creationist, which may explain his
amazing popular success as a TV personality. His science was
sometimes bogus as popularized science usually is. The science behind
a runaway greenhouse effect on Venus just isn't there.

--
I'm Trawley Trash, and you haven't heard the last of me yet.

On Sun, 21 Oct 2018 09:51:45 -0700, Trawley Trash
wrote:

On Tue, 16 Oct 2018 10:28:00 -0000 (UTC)
Mike Collins wrote:


Its a pity Brad Guths no longer here to read this.

https://www.businessinsider.com/nasa...share=1a1c01de


! The current climatic conditions and composition of the atmosphere are
! the result of a runaway greenhouse effect (an extreme greenhouse
! effect that cannot be reversed), which transformed the planet from a
! hospitable Earth-like "twin" world in its early history.

This comes from a speculative paper by Carl Sagan written around 1970.

Actually, it was proposed by Andrew Ingersoll, and it remains the most
widely accepted hypothesis for the evolution of the venusian
atmosphere. It is supported both by modeling, and by the very high D/H
ratio on Venus. In the case of Venus, water would have been the
driving greenhouse gas, not CO2.

The hypothesis may be wrong, but it is plausible, supported by
evidence, and far from "bogus science".

On Sun, 21 Oct 2018 15:26:01 -0600
Chris L Peterson wrote:

Actually, it was proposed by Andrew Ingersoll,

Possibly. I was intrigued by Sagan's paper on interstellar flight
and went to the UCLA library to look up everything Sagan had
written. This might have been on the same page or in the same
journal as something Sagan wrote, but I don't think so. Do you have
a reference?

Neither Sagan or Ingersoll seems to have their early serious
publications listed in wikipedia. That is as far as I can pursue it
now.

and it remains the most
widely accepted hypothesis for the evolution of the venusian
atmosphere.

Widely accepted among creationists perhaps. The idea that planets
originally held an earth-like atmosphere is absurd. Even the earth
didn't have that. In his video Ingersoll says Earth and Venus
originally had similar atmospheres and they evolved in different
directions. That is the same thing I am saying. Indeed all the
planets began with similar atmospheres and evolved in different
directions. It is noteworthy that Mars has a similar atmosphere to
Venus (just less of it). No runaway greenhouse effect there.

https://www.youtube.com/watch?v=zqmHWbPHDlI

It is supported both by modeling,

Ah, modeling. I can write computer models too. It shows that such a
thing is possible. Nothing more.

and by the very high D/H
ratio on Venus.

A high D/H ratio is exactly what you would expect if most of the
hydrogen were simply boiled away, as I suggested. It says nothing
about whether there was an ocean or not. The paper that
I read suggested that at one time an earth-like environment
prevailed on Venus, and the greenhouse effect made the water boil
away. It is not necessary to have had an earth-like environment in
the first place for the hydrogen to be driven off due to less
gravity and closer distance to the sun. The lighter isotopes will
always be driven away more quickly.

In the case of Venus, water would have been the driving greenhouse
gas, not CO2.

Point taken. My remark was about Venus being so
hot today: hotter than Mercury, hot enough to melt lead. What needs
to be pointed out is that at elevations with equivalent atmospheric
densities, Venus isn't hot. On earth every time we descend to a
lower elevation with higher pressure, the temperature increases: about
2C per thousand meters. On Venus it should be the same, but the
pressure at the surface is 92 times the pressure on the surface of the
earth. It is the atmospheric pressure and not the greenhouse effect
that keeps the surface of Venus so hot today.


--
I'm Trawley Trash, and you haven't heard the last of me yet.

On Sun, 21 Oct 2018 20:38:27 -0700, Trawley Trash
wrote:

On Sun, 21 Oct 2018 15:26:01 -0600
Chris L Peterson wrote:

Actually, it was proposed by Andrew Ingersoll,

Possibly. I was intrigued by Sagan's paper on interstellar flight
and went to the UCLA library to look up everything Sagan had
written. This might have been on the same page or in the same
journal as something Sagan wrote, but I don't think so. Do you have
a reference?

https://journals.ametsoc.org/doi/pdf...O%3E2.0.CO%3B2

and it remains the most
widely accepted hypothesis for the evolution of the venusian
atmosphere.

Widely accepted among creationists perhaps. The idea that planets
originally held an earth-like atmosphere is absurd.

The model does not presume much about the early atmosphere of Venus.
What it presumes is the early presence of liquid water on Venus.

On Mon, 22 Oct 2018 07:21:02 -0600
Chris L Peterson wrote:

This might have been on the same page or in the same
journal as something Sagan wrote, but I don't think so. Do you have
a reference?

https://journals.ametsoc.org/doi/pdf...O%3E2.0.CO%3B2

Thanks for the link to an original paper; I see that it references
a previous paper by Sagan which I have not read.
The Sagan paper I recall was a letter, about one page, possibly
discussing Ingersoll's results. Journal of atmospheric Sciences
sounds right. I will check this out at work where I have better
access to journals.

The model does not presume much about the early atmosphere of Venus.
What it presumes is the early presence of liquid water on Venus.

I have no problem here, but the results on thermal runaway on
Venus are often misconstrued to say that Venus once had an
earth-like atmosphere that went into thermal runaway due to
greenhouse effect. In his video Ingersoll shrugs this
off by saying perhaps in a billion years.

I remember crunching some numbers to estimate what percent CO2
would cause this to happen on earth, and it far exceeded 100%.
It is only possible on Venus, because its atmosphere is far
more dense than Earth's. Venusian air is so thick that a liter
of it would have a mass around 100g. Never, not even
in a billion years could this happen on earth.

--
I'm Trawley Trash, and you haven't heard the last of me yet.