Venus: Earth’s Sister Planet


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.

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