Professor Dave again, let’s check out Venus.
With Mercury down, it’s time to take a look at Venus, the second planet from the sun,
with an average orbital radius of 108 million kilometers.
Venus is the planet that is closest to the Earth, and it’s also the planet that is
the most similar to Earth in terms of size and mass, sometimes referred to as Earth’s
sister planet.
For this reason, we used to think that Venus might be a lot like the Earth in terms of
surface conditions, and could perhaps even be habitable.
This notion couldn’t be further from the truth, and we will see that the surface of
Venus is a hostile, nightmarish landscape.
Venus got its name from the Roman goddess of love.
But you won’t feel loved if you go for a visit.
Venus has an extremely thick atmosphere made almost entirely of carbon dioxide, which exerts
a pressure that is around one hundred times the atmospheric pressure on earth.
If you’re aware of escalating concerns regarding CO2 emissions here on our planet, you may
be surprised to find out that this gas makes up only 0.04 percent of our atmosphere, whereas
on Venus, it is a whopping 96 percent, with the rest consisting mainly of nitrogen and
then trace amounts of other gases.
As carbon dioxide is a greenhouse gas, which means it is very good at trapping in heat,
surface temperatures on Venus run up to 735 Kelvin, or around 863 degrees Fahrenheit.
This is the hottest surface temperature in the solar system, even hotter than Mercury,
despite the fact that Venus is farther away from the sun.
Apart from its thick atmosphere, Venus is also covered in clouds, and these are not
clouds of water vapor like on earth.
These clouds are made of sulfuric acid.
They are so thick that we can’t see the surface of the planet with telescopes, as
they strongly reflect the light from the sun, which is why Venus is so bright in the night
sky, and sometimes even visible in daylight.
Early observers knew Venus as either the “evening star” or the “morning star”, depending
on where Earth and Venus were in their orbits at any given time, resulting in Venus being
visible either after sunset or before sunrise.
The actual surface features of the planet were deciphered by the Pioneer Venus Orbiter
in 1978 using radar data, although actual images of the surface had been obtained a
few years prior, by the Venera landers, depicting a rocky landscape.
Data gathered later by the Magellan orbiter in the 90s gave us our first detailed map
of the surface, revealing a predominately flat surface, with just two regions of higher
elevation, sort of like earth’s continents.
These were called Ishtar Terra, for the Babylonian goddess of love, and Aphrodite Terra, the
Greek goddess of love that was renamed Venus by the Romans.
These land masses are about the size of Greenland and South America respectively.
Ishtar is also home to a mountain chain called Maxwell Montes, named after James Clerk Maxwell,
and which reaches an elevation of 11 kilometers above average surface elevation, significantly
taller than Mt. Everest.
Strong evidence of significant and fairly recent volcanic activity indicates that the
surface features on Venus are very new, much newer than Earth’s surface, and there may
even be active volcanoes to this day.
Going deeper, the core of the planet is probably made of iron like ours, but one thing about
Venus that differs dramatically is its magnitude and direction of rotation.
It takes Venus 243 days to spin one time around its axis, resulting in a solar day that is
117 earth days long.
Even more interestingly, it spins in the other direction from the other terrestrial planets,
so the sun rises in the west and sets in the east.
This is generally believed to be the result of a collision with a large planetesimal during
the formation of the solar system, though there are competing theories.
So that’s all we need to now about Venus for now, which means we are done with the
inferior planets, or those that orbit more closely to the sun than the Earth does.
That also means that it’s time to check out the Earth, our precious home.
Let’s move forward and learn about the formation of the earth and its moon, as well as some
of their features.