Above: the surface of the planet Venus, as seen beneath the dense cloud layer. The surface is probably grey
to black, but the yellow light filtering through the clouds gives it a yellow appearance. The large light-coloured
feature is a highland area called Aphrodite Terra (what I like to call The Dragon!). (Image map courtesy of
|Star System Sol - Planet Venus: Earth's evil twin
Above: a colour-coded map of Venus, red indicating high altitudes, blue
low altitudes. This map gives us an idea of what Venus might look like
without its punishing greenhouse effect, with oceans and vegetation and
continents. Indeed, maybe it was like this once?
Above: a Pov-Ray simulation of the surface of Venus - dark volcanic rocks bathed in yellow-orange light.
Above: intercloud lightning.
Above: the cloud-obscured orb of the planet Venus. The thick layer of clouds consists principally of an
aerosol of sulphuric acid! The sulphuric acid is formed by the action of sunlight on sulphur dioxide and
subsequent chemical reactions. The sulphur dioxide is possibly emitted by volcanic eruptions. Cloud map
courtesy of NASA.
The Structure of Venus
Venus is thought to have a similar structure to the Earth - with a hot silica-rich mantle and an iron-rich
core. The core is predicted to be just slightly larger than that of the Earth.
Above: a model of the predicted structure of Venus.
Life on Venus?
Venus is an unlikely place to find living things. The sulphuric acid is not the problem - there are bacteria
on Earth which excrete and thrive in sulphuric acid. The immense pressure is not a problem - although it
would splat you flat, there are creatures at the bottom's of the Earth's oceans who survive much greater
pressures (1100 Earth atmospheres!). These creatures are not crushed by the immense pressure since
they are adapted to these conditions and the pressure inside their cells is just as great, thus
counterbalancing the external pressure upon them. They also have special enzymes, since certain
chemical reactions (those involving a tiny increase in volume) are inhibited at such pressures. The
problem is the immense temperature. Even if liquid water existed under pressure, the heat would tend to
disrupt complex molecules. However, the clouds of Venus are cool and it is likely that certain bacteria can
survive and grow within the clouds. We also must ask ourselves if conditions are so harsh deep down
inside the planet's crust. However, even if a place can be found where bacteria-like organisms could
thrive, this does not mean that they would have evolved there - the temperatures really do seem
prohibitively high, but who knows?
Finally, we have to ask whether Venus was always this hostile to life. What happened, to make Earth's
twin such a fierce world? Was Venus once thriving with life?
Planet type: large terrestrial (0.82 Earth masses)
Equatorial Radius: 6052 km (0.95 Earth radii)
Equatorial Diameter: 12 104 km
Orbit: rotation axis inclined 177 degrees to ecliptic, retrograde rotation (the Sun rises in the West and sets in
the East), day is 243 Earth days in length. The day is longer than the year.
Atmosphere: about 96.5% carbon dioxide, 3.5% nitrogen, variable traces of sulphuric acid, 90-100 Earth
atmospheres of pressure. A 20 km deep cloud layer extends from 45 to 65 km altitude. It rains sulphuric acid
on Venus, but due to the immense surface temperatures, the sulphuric acid presumably decomposes before
reaching the surface. Cloud-to-cloud lightning is frequent in the atmosphere.
Surface Temperature: average 460 degrees C; hottest planet in the Solar System due to a runaway
Magnetic Field: Venus has almost no intrinsic magnetic field. Interactions between the solar wind and the
planet's ionosphere induces a weak magnetic field.
Natural Satellites: none.
Earth's evil twin
Venus is the closest planet to the Earth (apart from the Moon which is a planet-sized satellite of the Earth).
Venus is the closest planet, in the Solar System, to the Earth in terms of diameter and mass. Venus also has
a dense atmosphere with clouds and lightning, but their the similarity ends! Venus' atmosphere consists
almost entirely of carbon dioxide and is about 92 times as dense as the Earth's atmosphere. This very dense
carbon dioxide atmosphere traps in heat from the Sun's rays, raising the surface temperature to incinerating
temperatures. If you stepped onto the surface of Venus, then you would be squashed flat as a pancake and
incinerated instantly! You probably wouldn't have time to even notice the sulphurous fumes and suffocating