SCI 321 Research Project
July 28, 2012

Mercury - History and Naming Mercury, the planet closest to the Sun, circles the Sun faster than all the other planets in our solar system, which is why the Romans named it after the swift-footed messenger god Mercury (Space exploration, 2013). Human observers have been looking up at Mercury since at least the time of the Sumerians – the 3rd millennium BC (The planet mercury, 2013). These Greek astronomers believed even then that Mercury (and Venus) both orbited the Sun, and not the Earth. Mercury was the god of commerce, travel, and thievery in Roman mythology, hence the naming of Mercury.
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Early beliefs of Mercury Mercury was known since at least Sumerian times roughly 5,000 years ago, where it was often associated with Nabu, the god of writing (Mercury, the sun's, 2013). Mercury was also given separate names for its appearance as both a morning star and as an evening star (Mercury, the sun's, 2013). Early beliefs thought that perhaps there were two different planets. However, Greek astronomers knew that both names referred to the same planet (Mercury). Back in the nineteenth century, astronomers made very careful observations of Mercury's orbit, but they could not explain the orbit adequately using Newtonian mechanics (The planet mercury, 2013). There were discrepancies between what they observed and what was mathematics predicted. This problem would last for decades. Einstein's General Theory of Relativity correctly predicted the motions of Mercury; this led to the early acceptance of Einstein’s theory (The planet mercury, 2013).

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Mercury’s Important Facts Mercury is the closest planet to the Sun, therefore, its daytime temperatures can reach about 800°F, and drop down to -280°F at night (Mercury," 2013). This drop occurs because of the lack of much of an atmosphere on Mercury. This makes the weight of a man of my weight (175 lbs.) to be 66 lbs. on Mercury ("Mercury," 2013). The distance from the Sun to Mercury is a mere 35,983,095 miles, and the length of a Mercury year is 88 days (Mercury, 2013). The length of a day is 1,407 hours and 30 minutes, as opposed to Earths 24 hour day (Mercury, 2013). The length of one Mercury day (sidereal rotation) is equal to 58.646 Earth days. Because of the location in relation to the Sun, Mercury can really only been seen from the Earth around twilight.
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Mercury’s Size Mercury is 35.98 million miles from the Sun (The planet mercury, 2013). Mercury has a diameter of 3,032 miles, which is similar in size to the Earth’s Moon (Space exploration, 2013). The volume of Mercury is 0.054 of Earth (The planet mercury, 2013). The mass is 0.012 X 1027 ounces or 0.055 Earth’s mass (The planet mercury, 2013). The density is second after the planet Earth, with a large iron core having a radius of 1,100 to 1,200 miles, about 75 percent of the planet’s radius (Mercury, 2013). Unfortunately for Mercury, it is now the smallest planet since Pluto has been booted out and labeled a Dwarf instead.

Slide 5
Mercury’s size (Continued) This is a diagram from Space.com showing the diameter of inside the planet Mercury. Notice the effect of gravity on the basketball player in the left hand corner. I am not able to dunk a basketball for the 10’ needed for Earth; I can just imagine Lebron James dunking a basketball at 26’. This diagram also explains the rotation and the relationship to the earth (Mercury, the sun's, 2013).
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The Rotation of Mercury Mercury speeds around the sun every 88 Earth days, traveling through space at nearly 112,000 miles per hour (180,000 kilometers per hour), faster than any other planet (Space exploration, 2013). Its oval-shaped orbit is highly elliptical, taking Mercury as close as 29 million miles (47 million kilometers) and as far as 43 million miles (70 million kilometers) from the sun (Space exploration, 2013). If one could stand on Mercury when it is nearest to the sun, it would appear more than three times as large as it does when viewed from Earth (Space exploration, 2013) Oddly, due to Mercury's highly elliptical orbit and the 59 Earth days or so it takes to rotate on its axis, when on the scorching surface of the planet, the sun appears to rise briefly, set, and rise again before it travels westward across the sky (Space exploration, 2013). At sunset, the sun appears to set, rise again briefly, and then set again.

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Distances To/From Mercury
Average distance from the sun: 35,983,095 miles (57,909,175 km) By Comparison: 0.38 Earth's distance from the Sun.
Perihelion (closest approach to sun): 28,580,000 miles (46,000,000 km) By Comparison: 0.313 times that of Earth
Aphelion (farthest distance from sun): 43,380,000 miles (69,820,000 km) By Comparison: 0.459 times that of Earth Length of Day: 58.646 Earth days (Mercury, the sun's, 2013). These distances reflect the mileage that is needed to explore and research planets like Mercury. Mercury is often visible from Earth with binoculars and sometimes even the naked eye, however, Mercury is always very near the Sun and difficult to see (at the best time) in the twilight sky (The planet mercury, 2013). Earth observers can watch Mercury pass across the face of the sun, an event called a transit. These rare transits fall within several days of May 8 and November 10 (Mercury, 2013).
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Mercury’s Atmosphere Rather than an atmosphere, Mercury possesses a thin exosphere made up of atoms blasted off its surface by solar wind and striking micrometeoroids (Mercury, 2013). Because of the planet’s extreme surface temperature, the atoms quickly escape into space, therefore, with the thin exosphere, there has been no wind erosion of the surface and meteorites due not burn up due to friction as they do in other planetary atmospheres, like Earth (Mercury, 2013). Mercury possesses an exosphere containing 42 percent oxygen, 29 percent sodium, 22 percent hydrogen, 6 percent helium, 0.5 percent potassium, with possible trace amounts of argon, carbon dioxide, water, nitrogen, xenon, krypton and neon (Mercury, the sun's, 2013). With this composition, Mercury’s atmosphere is basically a vacuum and constantly needs to replace its atmosphere with most of its atmosphere constantly escaping into space, which results in the values of this composition continually changing (Mercury, facts and figures, 2013).
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Mercury’s Magnetic Field Mercury’s magnetic field is roughly 1 percent of that of the Earth. Although Mercury's magnetic field is just 1 percent the strength of Earth's, it is very active. The magnetic field in the solar wind — the charged particles streaming off the sun — periodically touches upon Mercury's field, creating powerful magnetic tornadoes that channel the fast, hot plasma of the solar wind down to the planet's surface (Space exploration, 2013). This breaks down the gravity to this; gravity on the surface of Mercury is 0.376 that of the Earth (The planet mercury, 2013).
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Mercury’s Internal Structure The surface of Mercury has enormous steep slopes and long cliffs from erosion or faulting (escarpments), some hundreds of miles in length and up to two miles high. Some of the cliffs cut through rings of craters and other surface features in such a way as to indicate that they were formed by compression. It is estimated that the surface area of Mercury shrank by about 0.1 percent. That would represent a decrease of about two thirds of a mile in the planet's radius (The planet mercury, 2013). One of the largest surface features is the Caloris Basin, which is about 800 miles in diameter. It seems to be similar to the large basins (seas or maria) on the Moon. Like those lunar basins, the Caloris Basin probably was caused by a very large impact early in the history of the Solar System. That impact may also have been responsible for the odd terrain on the exact opposite side of the planet (The planet mercury, 2013). In addition to its heavily cratered terrain, Mercury also has regions of relatively smooth plains. Some of the plains may be the result of ancient volcanic activity, but some may be deposits of dirt ejected from craters by impacts. A reanalysis of the old Mariner data revealed some evidence of recent volcano activity on Mercury (The planet mercury, 2013). Amazingly, radar observations from Earth of Mercury's north pole – a region not mapped by Mariner 10 – turned up evidence of water ice in the protected shadows of some craters (The planet mercury, 2013). Recent radar observations from Earth, reported in 2007, have shown that Mercury has a molten core. Once, scientists had thought the planet had a solid iron core until the interplanetary probe Mariner 10 discovered in 1974 that Mercury has a weak magnetic field, which indicated a molten core (The planet mercury, 2013).
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Research of Mercury The first spacecraft to visit Mercury was Mariner 10, which imaged about 45 percent of the surface and detected its magnetic field. NASA’s Messenger orbiter is the second spacecraft to visit Mercury, and has made three flybys as it slowly works its way into orbit (Space exploration, 2013). When it arrived in 2011, Messenger became the first spacecraft to orbit Mercury, where it studied Mercury for one year mapping nearly the entire planet in color (Space exploration, 2013). NASA has extended the mission beyond the initial one-year science plan to continue to study Mercury in more details. NASA seems to always find a way to continue exploration, even with considerable budget cuts.
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Mariner 10 Mariner 10 was the seventh successful launch in the Mariner series and the first spacecraft to visit Mercury. It was also the first spacecraft to use the gravitational pull of one planet (Venus) to reach another (Mercury), and the first spacecraft mission to visit two planets. The spacecraft flew by Mercury three times in a retrograde heliocentric orbit and returned images and data on the planet. Mariner 10 returned the first-ever close-up images of Venus and Mercury. The primary scientific objectives of the mission were to measure Mercury's environment, atmosphere, surface, and body characteristics and to make similar investigations of Venus. Secondary objectives were to perform experiments in the interplanetary medium and to obtain experience with a dual-planet gravity-assist mission 0((Mercury, facts and figures, 2013).
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Messenger
The Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) mission is designed to study the characteristics and environment of Mercury from orbit (Mercury, facts and figures, 2013) and composition of Mercury's surface, the geologic history, the nature of the magnetic field, the size and state of the core, the volatile inventory at the poles, and the nature of Mercury's exosphere and magnetosphere over a nominal orbital mission of one Earth year (Mercury, facts and figures, 2013). The mission should also yield global composition maps, a 3-D model of Mercury's magnetosphere, topographic profiles of the northern hemisphere, gravity field to degree and order 16, altitude profiles of elemental species, and a characterization of the volatiles in permanently shadowed craters at the poles (Mercury, facts and figures, 2013)
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Messenger Flyby in 2011
This photo was taken by NASA’s Messenger on March, 3rd, 2011 on a flyby. You can see the smoothness of the plains and not a whole lot of color in the photo. The surface looks similar to the Earth’s moon in appearance and is also similar in size to the Earth’s moon. There appears to be some craters which would indicate that there had been collisions in the past at some point. NASA is still studying Mercury and can determine its past better after analyzing photos like these.
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Conclusion:
MESSENGER will map Mercury by taking pictures of the planet’s surface, including some areas that have not been seen before. It will also collect data on the composition of the surface rocks, and measure the heights of mountains and depths of craters and valleys. Some data collected by MESSENGER will help scientists to understand what the inside of Mercury is like. MESSENGER will let people learn more about Mercury than they ever have before (Mercury, facts and figures, 2013).

References

Home. (2013, July 06). Retrieved from http://www.nasa.gov/home/index.html
Mercury. (2013, July 06). Retrieved from http://science.nationalgeographic.com/science/space/solar-system/mercury-article/
Mercury, the sun's closest planetary neighbor. (2013, July 06). Retrieved from http://www.space.com/36-mercury-the-suns-closest-planetary-neighbor.html
Space exploration. (2013, July 06). Retrieved from http://spaceexplora.blogspot.com/
The planet mercury. (2013, July 06). Retrieved from http://www.spacetoday.org/SolSys/Mercury/ MercuryBackground.html

Photo References
Home. (2013, July 06). Retrieved from http://www.nasa.gov/home/index.html

Mercury, the sun's closest planetary neighbor. (2013, July 06). Retrieved from http://www.space.com/36-mercury-the-suns-closest-planetary-neighbor.html

Image References
NASA. 2013, http://1.bp.blogspot.com/-vDKkKGDekXE/T-imhd3b6xI/AAAAAAAAAAk/8ppeX_2m7x8/s400/venus-planet-profile-
101111-02.jpg
NASA. (Photographer). (2012, November 29). A mosaic of messenger images of mercury’s north pole region [Web Photo]. Retrieved from http://www.nasa.gov/mission_pages/messenger
NASA. http://nssdc.gsfc.nasa.gov/image/spacecraft/mariner10.gif
NASA. http://solarsystem.nasa.gov/missions/images/miss-messenger.jpg
NASA.2011,http://www.nasa.gov/images/content/592866main_messenger_orbit_image20110929_8_4by3_946-710.jpg
NASA.2011,http://www.nasa.gov/images/content/281528main_flyby2_20081007_540.jpg NRAO, 1991 [Print Photo]. Retrieved from http://images.nrao.edu/Solar_System/Planets/113

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"Mercury, facts and figures," 2013)
When it arrived in March 2011, MESSENGER became the first spacecraft to orbit Mercury, where studied Mercury for one year, entire planet in color. NASA has extended the mission beyond the initial one-year science plan to continue MESSENGER orbiter is the second spacecraft to visit Mercury, and has made three flybys as it slowly works its way into orbit. When it arrived in March 2011, MESSENGER became the first spacecraft to orbit Mercury, where studied Mercury for one year, mapping nearly the entire planet in color. NASA has extended the mission beyond the initial one-year science plan to continue to study Mercury NASA's MESSENGER orbiter is the second spacecraft to visit Mercury, and has made three flybys as it slowly works its way into orbit. When it arrived in March 2011, MESSENGER became the first spacecraft to orbit Mercury, where studied Mercury for one year, mapping nearly the entire planet in color. NASA has extended the mission beyond the initial one-year science plan to continue to study Mercury's MESSENGER orbiter is the second spacecraft to visit Mercury, and has made three flybys as it slowly works its way into orbit. When it arrived in March 2011, MESSENGER became the first spacecraft to orbit Mercury, where studied Mercury for one year, mapping nearly the entire planet in color. NASA has extended the mission beyond the initial one-year science plan to continue to study Mercury The first spacecraft to visit Mercury was Mariner 10, which imaged about 45 percent of the surface and detected