Dear dee_vanhorn,
I've copied the answer to your question (listed below) from the following site: http://coolcosmos.ipac.caltech.edu/cosmic_kids/AskKids/mercury_discovery.shtml
"Who discovered Mercury?
There is no single person who is credited with the discovery of Mercury. Mercury is one of the five planets that can be seen in the night sky without using a telescope or binoculars. The planet Mercury has been known since ancient times and was observed for thousands of years by the people of many different cultures. One of the earliest records of Mercury comes from the Sumerians around 3,000 BC. Since Mercury never travels far from the sun in the sky, it is more difficult to see and was probably discovered later than brighter planets like Venus, Mars, Jupiter and Saturn."
The following site goes into better details about Sumerian, Babylonian, and Chaldean records (All located in the Fertile Crescent--Middle Eastern region) and times: http://visav.phys.uvic.ca/~babul/AstroCourses/P303/mesopotamia.html
The earliest people to know about the planet Mercury were the Mesopotamians (the first known cradle civilization in the Middle East--over 5,000 years ago--give or take a few years). They passed on their beliefs to the Babylonians and Sumerians when they moved into the region (and they, of course, added to that knowledge).
One of the races that existed around that time was the Chaldeans. They built temple towers called ziggurats [Ziggurats are associated with Sumerians, Babylonians, Assyrians, and Chaldeans--all part of the Fertile Crescent/Mesopotamia.)to reflect their cosmogony. One of these temple tower designs might have been the blue print for the famous Tower of Babel mentioned in the Bible. Even though this structure doesn't exist anymore, there is a good chance that it did at one time because there have been many events mentioned in the Bible that have since been confirmed as possibly having a basis in reality by scientists who've compared writings of other cultures, like the Egyptians, and have found corresponding events. I've copied a paragraph that I found on the following site for your perusal (It mentions that the Babylonians not only knew about Mercury--and other planets--but also used knowledge of these celestial bodies to help them design their temples:
http://www.whitedragon.org.uk/articles/starlore.htm
"In the search for a plastic expression of their cosmogony, the Chaldean rulers devised the temple tower, the ziggurat. Built in steps, it expressed the degrees of the hierarchy on which heaven and earth were established. The ziggurat was actually a miniature world; its structure represented the ?Mountain of Earth?. In Babylon they erected the El-Temen-An-Ki, the house of the foundation stone of heaven and earth. This magical monument, known in the Bible as the Tower of Babel, had seven stages, each one dedicated to a planet. Its angles symbolized the four corners of the world, pointing to Akkad, Suburtu, Elam and the western lands. Four, according to old Sumerian traditions, was the number of the heavens, and the square or rectangle was accepted by Babylon as the basis of their system. The seven steps of the tower were painted in different colours which corresponded to the planets. The ?Great Misfortune?, Saturn, was black. Saturn, the ?Nightly Sun?, was at the base, opposed to the highest degree, the gilded top of the tower where the sun resided. The second storey up was white, the colour of shining Jupiter; the third, brick-red, the colour of Mercury. Then followed blue for Venus, yellow for Mars, gray or silver for the moon. These colours boded good or evil, like their planets."
I thought you might find this information interesting as well: http://home.cwru.edu/~sjr16/advanced/pre20th_ancients_egyptians.html
"Astronomical Ceiling of Senmut
The earliest known astronomical ceiling is that in the tomb of Senmut, the architect and favorite of Queen Hatshepsut (~1473 B.C.). A decan list is present, showing unmistakably that a star clock was copied. The last decan is Sirius-Sothis and have positions such that the star clock copied on the ceiling must be dated to the last revision in the Twelfth Dynasty, 400 years earlier.
Besides the decan list, there are stars and deities present. The constellations of the ship, sheep, Osiris (Orion) and Isis are also present. To the left of the decans, where a star clock would continue with the triangle decans for epagomenal days, Senmut has a mixture of decans and planets. Jupiter and Saturn are before the triangle decans as two falcon-headed figures, and Mercury and Venus follow the decans where Mercury is represented as Seth and Venus as a heron.
The Ceiling of Senmut is also the first place in which all the known planets (Mercury, Venus, Mars, Jupiter, and Saturn) except Mars appear. Mars appears with the others in the astronomical ceiling of Ramesseum 200 years later. Jupiter, Mars, and Saturn were usually separated from the other two, Venus and Mercury, and were tied to the sky god Horus."
Mercury had the simplest name of the planets, Sbg, though its meaning is unknown. It was frequently associated with Seth, the enemy of Horus and murderer of Osiris. A text which dates to the era of Ramses VI (1148-1138 B.C.), refers to Mercury as "Seth in the evening twilight, a god in the morning twilight," conclusively showing that it was recognized as the same object in both the morning and evening."
This website lists several other cultures who were aware of the planet Mercury long before the Europeans. Feel free to check it out for yourself: http://btc.montana.edu/ceres/MESSENGER/ancastro.htm
So, as you can see, mankind will never know the name of the person who first discovered Mercury because he/she lived over several thousands of years ago. We can only know that Sumeria was the where, around 3,000 B.C. was the when, and the how was through observation of the night sky.
I hope that helps.
Mic Sayre