Mercury

Mercury, the planet nearest the Sun, is the second smallest planet in our solar system. Only slightly larger than the Earth's moon, Mercury's surface is covered with craters. This tiny planet does not have any rings or moons.

Basic Facts

	Mercury	Earth
Position from the Sun	1	3
Diameter	3,031 miles (4,878 km)	7,926 miles (12,753 km)
Moons	0	1
Rings	0	0
Average Distance from Sun	36,000,000 miles (58,000,000 km)	93,000,000 miles (149,000,000 km)
Your Weight on the Planet	Multiply your weight by 0.38	Multiply your weight by 1.0
Length of One Year	88 Earth days	365 Earth days
Length of One Day	59 Earth days	1 Earth day
What’s in the Atmosphere?	Sodium, helium, hydrogen, oxygen	Nitrogen, oxygen
Temperature	-280ºF to 800ºF (-170ºC to 430ºC)	-128ºF to 136ºF (-89ºC to 58ºC)

Discovery

Mercury's orbit is so close to the Sun that it is difficult to see. This explains why some early astronomers didn’t see it. Viewed from Earth, Mercury is never far from the Sun in the sky. Because the Sun is so bright, Mercury can only be seen in twilight.

Timocharis made the first recorded observation of Mercury in 265 BC.

Missions to Mercury

Mission	Launch Date	Arrival Date	Mission Accomplishments
Mariner 10 (USA)	November 3, 1973	March 29, 1974	Took 10,000 pictures, covered 57% of Mercury

Interesting Facts About Mercury

	Fastest orbiting planet
	The side of Mercury facing the Sun can reach temperatures of 800ºF while the side facing away from the Sun can get as low as -280ºF at the same time.

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Space: Today, Tomorrow, and Always

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