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Mars? , Venus?

The planet
Mercury


Not a popular tourist destination at present (2001/11), because the planet is a bit close to the SUN! Orbital period 88 days. It's a small planet, so is a bit short on atmosphere.

The planet Mercury orbits the sun every 88 days. Although it is very hot on the day side of the planet Mercury, the night side is very cold. A while ago it was believed that the planet was gravity-locked to the sun so the same face of it was pointing sunwards. This would have meant that there was a Twilight Zone of fixed terrain where it was neither hot nor cold! Current evidence suggests that the rotational period is locked into a rhythm such that the day length is 176 Earth days* (two Mercury years). This would mean that any such Twilight Zone would move around the planet at a speed of 3.63Km/hour.

* Some websites incorrectly state the length of the day on Mercury to be 58 days. That's the Sidereal day. (The sidereal day on Earth is 23 hours 56 minutes 4.1 seconds). If we count day length in terms of time of sunrise to the next sunrise, on Earth it's 24 hours, and on Mercury it's 176 earth days.

Here are a few links:

http://en.wikipedia.org/wiki/Mercury_(planet)

wwwflag.wr.usgs.gov/USGSFlag/Space/wall/mercury.html

http://pds.jpl.nasa.gov/planets/welcome/mercury.htm

http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/mercury.html

http://csep10.phys.utk.edu/astr161/lect/mercury/mercury.html

http://science.nationalgeographic.com/science/space/solar-system/mercury-article/ - well done to National Geographic

http://spacelink.nasa.gov/Instructional.Materials/Curriculum.Support/Space.Science/Our.Solar.System/Mercury/.index.html (gone but relinked to NASA)

Mariner 10: http://nssdc.gsfc.nasa.gov/nmc/tmp/1973-085A.html (gone)

http://cps.earth.northwestern.edu/merc.html

These were last checked 2012/04/19

It was said a while ago that the Planet mercury took 88 days to orbit the sun, but that there was another planet, the Planet Vulcan orbiting even closer to the sun, taking only 28 days to orbit the sun.