The History of Mercury
The Babylonians recorded early writings describing Mercury in 3,000 B.C. The Greeks referred to Mercury as Apollo when viewed as the morning star, and Hermes when it was viewed as the evening star. Since this time, the innermost planet in the solar system has always fascinated astronomers. Anyone up to date on their Roman mythology would know the planet was named after the Roman god Mercury, who was the “winged messenger of the gods” and responsible for travel and merchants. It is said that the planet Mercury was given this name because it is the fastest planet to orbit around the sun. As the second smallest planet, Mercury is 4,879 kilometers (3,025 miles) in diameter and has no moon.
The Orbit Of Mercury
The orbit of Mercury is different than the orbit of Earth. The perihelion, or point at which the planet is closest to the sun, is 46 million kilometers (29 million miles), whereas, its aphelion, or point at which the planet is farthest from the sun is 69 million kilometers (43 million miles).
Based on this, the orbit of Mercury is elliptical or egg-shaped. This is in comparison to the Earth’s orbit, which is circular in shape with the perihelion and aphelion being 91 and 94 kilometers respectively from the sun.
As previously stated, Mercury is one of the fastest planets to orbit the sun. It moves at a speed of 48 kilometers (30 miles) per second. Based on this, a phenomenon appears to occur when Mercury is at its perihelion in which the sun seems to be moving eastward for a short period of time, and then continues to move westward.
The orbit of Mercury is once every 88 Earth days while its rotation on its axis is 58.6 days on Earth, as discovered in 1965. Therefore, Mercury will complete three rotations during two orbits of the planet (Zuber 2004).
Expeditions To Mercury
The only known expedition to Mercury to take photos of the planet was the Mariner 10 spacecraft, which traveled around Mercury during March 1974 to March 1975.
Mariner 10 was able to fly by a total of three times and collect pictures on about 45 percent of Mercury’s surface. The spacecraft was also able to detect sodium in Mercury’s atmosphere, and a magnetic field that was not thought to exist. It was discovered the magnetic field of Mercury is 1% of Earth’s magnetic field.
In 2004, the Messenger probe was launched by the United States, and is expected to visit Mercury in the year 2008, 2009, and orbit around the planet in 2011. It will be used to determine a clearer view of the surface and composition of the planet (Zuber 2004).
Exploring A Day On Mercury
The first thing someone would notice while exploring Mercury is the darkness. The darkness is the result of the very small amount of atmosphere available. Due to the small amount of gravity on the planet, whatever atmosphere it is able to hold onto consists of sodium, potassium, helium, oxygen, and hydrogen. Therefore, even though Mercury is the closest to the sun, a day on the planet would be a dark one.
The temperatures on Mercury would be something to become accustomed to as well. As the closest neighbor to the sun, Mercury experiences temperature ranges of –200 to +800 degrees Fahrenheit. Compared to the other innermost planets, Mercury has the highest degree of variation between its day and night temperatures.
The second feature a person would notice spending a day on Mercury would be the ragged landscape. Johann Hieronymus Schroeter, who lived from 1745 to 1816, is credited with being the first to draw sketches of the planet. The surface of Mercury is generally wrinkled in appearance. Pictures sent back from the Mariner 10 space shuttle showed a surface similar to Earth’s moon with noticeable craters, which have been formed by asteroids colliding into it. The surface shows small and large craters with the small craters approximately 10 kilometers (6 miles) in diameter. Whereas the larger craters, have measurements of 100 kilometers (60 miles) or greater in diameter. Many of these large craters resemble a “bull’s eye” or multiring basin when viewed by Mariner 10. The most popular of the larger craters is the Caloris basin, which is approximately 1300 kilometers (810 miles) in diameter, and a fairly young multiring basin.
Also located on the surface of Mercury are smooth flat plains, which are interspersed among the craters. It is the general belief these intercrater plains are thought to have been formed by early volcanic activity.
As someone would continue to explore the interior of Mercury, it would be possible to view the more than hundred scarps that dot the planet’s surface. Scarps are cliffs, which have been formed along fault lines resulting in one side of the land rising higher than the other. They are found on 45 percent of Mercury’s surface and are approximately 3 kilometers (2 miles) in height and 100 meters in length.
Of noticeable mention about the planet Mercury is that it might contain water ice at its Northern and Southern poles. There is a large debate about how a planet this close to the sun, and with temperatures this hot, could have water ice at its poles. Proponents to the belief that water ice exists on Mercury state the ice is probably located at the bottom of deep craters where temperatures are considerably cold enough to maintain ice. However, opponents to the belief of the existence of water ice on Mercury feel that the substance might actually be sulfur, which is in abundance in the solar system.
However, even if water did exist on Mercury this should not lead you to think the planet would be able to sustain human life. With virtually little atmosphere, and temperatures ranging form –200 to +800 degrees Fahrenheit, this would make it hard for humans to survive (Zuber 2004).
Statistics About Mercury
| Discovered By | Known by the Ancients |
| Date of Discovery | Unknown |
| Average Distance from the Sun | Metric: 57,909,175 km English: 35,983,095 miles Scientific Notation: 5.7909175 x 107 km (0.38709893 A.U.) By Comparison: Earth is 1 A.U. (Astronomical Unit) from the Sun. |
| Perihelion (closest) | Metric: 46,000,000 km English: 28,580,000 miles Scientific Notation: 4.600 x 107 km (0.3075 A.U.) By Comparison: 0.313 x Earth |
| Aphelion (farthest) | Metric: 69,820,000 km English: 43,380,000 miles Scientific Notation: 6.982 x 107 km (0.4667 A.U.) By Comparison: 0.459 x Earth |
| Equatorial Radius | Metric: 2,439.7 km English: 1,516.0 miles Scientific Notation: 2.4397 x 103 km By Comparison: 0.3825 x Earth |
| Equatorial Circumference | Metric: 15,329.1 km English: 9,525.1 miles Scientific Notation: 1.53291 x 104 km |
| Volume | Metric: 60,827,200,000 km3 English: 14,593,200,000 mi3 Scientific Notation: 6.08272 x 1010 km3 By Comparison: 0.054 x Earth's |
| Mass | Metric: 330,220,000,000,000,000,000,000 kg Scientific Notation: 3.3022 x 1023 kg By Comparison: 0.055 x Earth's |
| Density | Metric: 5.427 g/cm3 By Comparison: 0.984 x Earth |
| Surface Area | Metric: 74,800,000 km2 English: 28,900,000 square miles Scientific Notation: 7.48 x 107 km2 By Comparison: 0.108 x Earth |
| Equatorial Surface Gravity | Metric: 3.7 m/s2 English: 12.1 ft/s2 By Comparison: If you weigh 100 pounds on Earth, you would weigh 38 pounds on Mercury. |
| Escape Velocity | Metric: 15,300 km/h English: 9,500 mph Scientific Notation: 4.25 x 103 m/s By Comparison: Escape Velocity of Earth is 25,022 mph |
| Sidereal Rotation Period (Length of Day) |
58.646 Earth days 1407.5 hours By Comparison: By Comparison: 58.81 x Earth |
| Sidereal Orbit Period (Length of Year) |
0.241 Earth years 87.97 Earth days By Comparison: 0.241 x Earth |
| Mean Orbit Velocity | Metric: 172,341 km/h English: 107,088 mph Scientific Notation: 47,872.5 m/s By Comparison: 1.61 x Earth |
| Orbital Eccentricity | 0.20563069 By Comparison: 12.3 x Earth |
| Orbital Inclination to Ecliptic | 7 degrees |
| Equatorial Inclination to Orbit | 0 degrees By Comparison: Earth's equatorial inclination to orbit is 23.45 degrees. |
| Orbital Circumference | Metric: 356,000,000 km English: 221,000,000 miles Scientific Notation: 3.56 x 108 km By Comparison: 0.385 x Earth |
| Minimum/Maximum Surface Temperature | Metric: -173/427 °C English: -279/801 °F Scientific Notation: 100/700 K By Comparison: Earth's temperature range is ~ 185/331 K. |
| Atmospheric Constituents | By Comparison: Earth's atmosphere consists mostly of N2, O2 |
| Table 1: Concise statistics on the planet Mercury (N.A.S.A. 2006) | |
References
Encyclopedia Britannica. “Mercury.” 2006. Encyclopedia Britannica Premium Service. 2006
http://www.britannica.com/eb/article-241980
National Aeronautics and Space Administration (N.A.S.A). “Mercury: Facts & Figures.” 2006.
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mercury
Zuber, Maria T. “Mercury.” World Book Online Reference Center. 2004. World Book, Inc.
http://www.worldbookonline.com/wb/Article?id=ar356240
Mercury Images
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