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--------------------------- - 1873 - Venus and Mercury.
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- Venus and Mercury are the two rocky planets closer to the Sun. It really shows on Venus where temperatures on the surface reach 480 degrees C. The surface atmospheric pressure is 92 times greater than that found on Earth. The high temperatures are not just because it is closer to the Sun. It is shrouded in a thick blanket of clouds of sulfuric acid that trap the heat in a greenhouse effect.
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- Size wise Venus is just 5% smaller than Earth. A sister planet with such a harsh environment it could not have hosted life as we know it. Venus has a similar composition to Earth but has no evidence of plate tectonics like Earth that continuously recycles the planet’s crust. Yet, Venus has volcanoes and lava flows, so, there is evidence of the planets inner activity and dynamics.
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- The atmosphere of Venus is equally fascinating. The planet rotates so slowly, once ever 224 days, and opposite to the planets motion around the Sun, a retrograde rotation. However, Venus’ clouds circulate once every 4 days, up to an altitude of 56 miles. At the poles this atmospheric rotation creates a spectacular vortex, like the eye of a hurricane.
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- Venus has many mysteries . We need to learn more. But, it’s hostile environment is not good biology for life. So, to date science research has not given it much attention. “Venus Express” launched in 2005 was our last attempt with a space probe.
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- Mercury had the “Messenger” spacecraft in 2011 that orbited the planet 4,000 times. This probe gave us a topographic map of Mercury’s craters, ridges, volcanoes, and mountains that were 2 miles high.
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- Mercury too has had volcanic activity and lava flows, some 60% the size of the United States. Today the surface is shrinking due to the steady cooling of its core over time. Evidence of this is the buckled crust and a ridge running diagonally across its surface. Estimates are that this core cooling has reduced Mercury’s diameter by 8.5 miles since the planet formed.
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- Unlikely as it may seem, in the north pole shadows , Mercury has areas containing water ice. Mercury is 450 degrees C at the equator, but, there are parts of the poles that are continuously in the shadows. Because Mercury has no atmosphere to transport the heat around the planet this type of location could remain extraordinarily cold., sunlight never reaches it.
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- This water likely arrived from asteroids and comets impact that came from the outer solar system.
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- Mercury has a surprisingly volcanic history. It surface has channels, hills and vents formed by ancient volcanoes that are 3.5 billion years to as recent as 1 billion years old.
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- Mercury is extremely dense compared to Earth. It has a disproportionably large iron-rich core, 60% of the planet’s mass. It is possible that a large impact 4.5 billon years ago ripped off its crust and mantle. After all our Moon resulted from a large impact that splashed Earth’s curst into orbit.
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- With little crust Mercury’s more volatile elements, like sulfur and ammonia, have vaporized away. However, other volatiles like potassium, sodium, and chlorine have high levels on the surface. The possible explanation is that the huge impact was at a very low angle ejecting material into space but not creating the heat needed to boil off all the volatiles.
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- Mercury’s magnetic field is strangely off center, off by about 20% of the planet’s radius, shifted to the north. Unlike Venus, Mars, and our Moon, Mercury has a distinct magnetic field of its own. Again, this could be the result of the flow of the iron in its outer core.
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- April 30, 2015 the Messenger spacecraft crashed into Mercury’s surface creating a 52 foot-wide crater. The next Mercury space probe is planned for 2024, named BepiColombo.
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- Request these Reviews to learn more about Mercury:
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- #1815 - Mercury is 26% the diameter of Earth. Plus there are 9 other Reviews listed.
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-- Request these Reviews to learn more about Venus:
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- #1778 - Venus has somehow managed to turn itself inside-out leaving no craters on the surface. Plus there are 7 other Reviews listed.
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- If you were on Venus you could walk and keep up with the stars overhead.
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- 75% of the sunlight that hits Venus bounces back before ever reaching the surface.
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----- 707-536-3272 ---------------- Wednesday, May 18, 2016 -----
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