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.