Venus is the 2nd planet from the Sun and is named after the Roman goddess of
love and beauty - perhaps because it shone the brightest of the five planets
known to ancient astronomers - but looks can be deceptive, Venus has no love for
the human body!
The surface temperature of Venus is up to
465oC.
The surface atmospheric pressure is 90
atm (90 x that on Earth).
The lower atmosphere is mainly carbon
dioxide (96.5% CO2) and nitrogen (3.5% N2).
[in the lower atmosphere and upper
clouds there may be small amounts of sulfur dioxide (SO2),
oxygen (O2), water (H2O), noble gases - helium
(He), neon (Ne) & argon (Ar), carbon monoxide (CO), sulfuric acid (H2SO4),
basalt rock particles and iron(III) chloride (FeCl3)]
The surface area and volume are about 0.9
x that of Earth.
On Venus it rains sulfuric acid, but this
evaporates before reaching the very hot surface
The surface of Venus is dry because it is
too hot for liquids to condense on
The surface of Venus is relatively flat
but very volcanic with still some active volcanoes.
The dense lower carbon dioxide atmosphere is
encased in 80 km thick clouds of mainly sulfuric acid (H2SO4)
and some sulfur dioxide (SO2) - these clouds reflect 90% of
sunlight - which is why it seems so bright, as well as being closer to the
Sun than the Earth.
This reflection of sunlight would tend to
make the planet cooler - a global dimming effect.
BUT, the hot surface of over 460oC
is a powerful emitter of infrared EM radiation.
This thermal radiation is absorbed by
the lower carbon dioxide rich atmosphere (96.5% CO2).
This produces a super greenhouse
effect compared to planet Earth (0.04% atmospheric carbon dioxide).
Little (if any?) infrared
radiation escapes from the planet's atmosphere.
So the surface temperature is kept at a
much higher temperature than if the infrared could escape and the net effect
completely overrides the dimming effect of the outer reflective clouds.
Note:
(a) Compared to Earth the surface
temperature is much hotter - a much stronger emitter of infrared EM
radiation AND the atmospheric carbon dioxide concentration is 2400 x
that of Earth! - 2400 x the greenhouse effect of carbon dioxide gas
on Earth!
(b) The greenhouse effect on
Venus is different to that on Earth in one respect - it doesn't
actually involve the absorption and remission of infrared radiation
- the infrared source on Venus is only from the hot surface.
