Venus Answers

by Deb on June 10, 2012

Venus surface

And to round off the Venus saturated week, a bit of information on the actual planet rather than just how to watch it. Have a look at the questions if you missed them.

1.     The morning and evening stars were known to a lot of ancient cultures as they are fairly obvious – the brightest object in the night sky after the moon. Judging from surviving fragments the Babylonians knew that they were both the same planet, however the later Greeks thought they were different. Pythagoras is credited with showing that they are a single planet, but that may be a case of something that happened around that time being attributed to a famous figure.

Venus and moon crescents

2.     I think the prize for best answer has to go to Wanderlust,

Venus is extremely hot, which is why she’s always surrounded by cherubs and lusty suitors.

And now for the boring facts. Venus is actually the hottest planet in the solar system, but she was named after the Goddess of love before they knew that. She is even hotter than Mercury because Mercury has a night side that rarely sees the sun and no atmosphere to spread it around, so it gets down to -220 degrees in the dark. Venus has an extremely thick atmosphere so although she is much further out than Mercury she gets to 460 degrees.

That thick atmosphere is the problem. It is 93 times the mass of Earth’s and it’s over 96% carbon dioxide. To put that in context, Earth’s atmosphere is about 0.04% carbon dioxide. This means Venus has a massive runaway greenhouse effect and makes it the hottest thing in the solar system after the Sun.


3.     Venus is covered in massive thick clouds of sulfur dioxide and sulfuric acid, so we didn’t learn much about her rotation until probes with radar that could peer beneath them went there in the 20th century. It turns out to be very strange indeed. Venus has what is called a retrograde rotation – it rotates in the opposite direction to its orbit, so the sun rises in the west and sets in the east.

On top of that it rotates extremely slowly, rotating once every 243 earth days while it only takes 224.7 earth days to orbit. It sounds like its ‘day’ should be longer than its year, but it doesn’t quite work that way. The time from sunrise to sunrise is influenced by the orbit as well as the rotation, and it makes Venus’ day shorter – only 116.8 earth days! This means that in a Venusian year you would have 1.9 Venusian days.

It is possible that Venus formed with this type of rotation, or it could have been from a massive collision in the early solar system.

4.     Venus is often called Earth’s sister or twin because the two planets are very similar in size and build. Venus’ radius is 95% of Earth’s, and volume is about 85%. However the similarities appear to end there. Because of the massive heat any water has long evaporated and broken up, and the free hydrogen lost to the solar wind because there is no magnetic field to protect it.

Venus has an active mantle, crust and core like Earth’s, but water acts as the lubricant for tectonic movement on Earth which releases a lot of heat from the core. Venus does not have this movement so it seems that the heat builds up in the mantle until it is so hot that there are massive lava flows that can resurface the entire planet. This seems to have happened 300-500 million years ago.

5.     In spite of the incredibly hostile conditions, probes have made it to the Venusian surface and even sent photos back. The photo up the top is from the Soviet Venera 13 probe that landed in 1982, part of it can be seen in the bottom right. No probe has lasted more than an hour in the intense heat, pressure and acid environment.

In spite of the fact that Venus is closer, Mars is going to be a far more successful planet to explore.

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