cheerfulgreek |
03-05-2008 03:00 AM |
Quote:
Originally Posted by srmom
(Post 1612085)
Actually, this is incorrect, according to astrophysicists, Mercury (the closest planet to the sun) and Venus (2nd closest) are the hottest planets and it is because of their proximity to the sun.
Venus is thought to be the hottest planet, and one theory espoused by many scientists is that Venus, being closer to the sun, was subjected to a so-called runaway greenhouse effect, which caused any oceans to evaporate into the atmosphere.
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Uhmm... o.k. Let me get this straight. My previous post said that planets closer to the sun don't necessarily mean they're warmer. You said that was incorrect, but yet you post that Venus is the 2nd closest planet to the sun, but it's the hottest.:confused: That was my point (duh).:rolleyes: Mercury is the closest to the sun but it is not the hottest.
The sun does have a major effect on the surface of the planets, but there are other factors involved. Mercury orbits around the sun every 88 days within about 29 million miles away from the sun, which causes 700 degree surface temperatures hot enough to melt lead. At one time it was believed that Mercury had an identical day and year rotating once every time it completed an orbit around the sun so that it kept one side permanently facing the sun, somewhat like our moon as it orbits Earth. This is called synchronous rotation. Actually it's sort of strange, but Mercury's day is about two thirds of it's year which is about 50-60 Earth days (I think) so it actually rotates three times for every two trips around its orbit. This has an effect on the surface temperature because for the most parts of Mercury, the sun rises across it's sky once every two years, about 170-180 Earth days.
Venus's surface is hotter than Mercury's at over 850 degrees but yet it's further away from the sun than Mercury is (like you said). The reason why, is because Venus actually rotates once every 243 Earth days while it orbits the sun in 225 Earth days, so it's day is longer than it's year. Venus's slow rotation is also done in the opposite direction to almost every other planet in our solar system, it's also technically upside down on it's axis. All of this has an effect on sunrise to sunrise which effects it's surface temperature, and makes it warmer than Mercury.
Now, the information you posted about Venus having water at one time, is incorrect. Scientists thought this because there's about a 26 million mile difference between Venus and Earth's orbits. The 1st space probes to fly past Venus found that the atmosphere was pretty much carbon dioxide with clouds made of sulphuric acid. The probes also provided accurate information that the surface was made up of volcanic rock. Hardly a planet that could have had water running across its surface.
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