09_Mercury - GEL36 SOLAR SYSTEM Lecture 9 Mercury(Ch 21...

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1 GEL36 SOLAR SYSTEM Lecture 9: “Mercury” (Ch. 21) Goal of the Lecture: To discuss the characteristics and history of Mercury in the context of similarities and differences with the Moon and Earth. General characteristics Closest planet to the sun and the smallest (now that Pluto’s been demoted). - whenever you want to see Mercury, you always have to look toward the sun because Mercury orbits the sun so closely. Mercury is always up in the daytime sky, but our view is obscured by the glare of the Sun. So in order to see it you have to look toward the horizon after sunset or in the dawn sky just before sunrise when the sun’s brightness is masked by the edge of the Earth. - during May, 2011, Mercury is visible in the east about 30 minutes before sunrise. Till recently, almost all of the information we had about Mercury was gathered in 1974- 75 by the Mariner 10 spacecraft that did three flybys of the planet - Mariner 10 mapped and photographed ~45% of the planet. The other face has never been seen by a spacecraft until this March 2011. NASA launched the $286 million " Messenger " in July 2004, that eased into orbit in March 2011 after two flybys in 2009. Fierce heat and solar gravity make the trip difficult, but a sun-blocking parasol helps. (ME rcury S urface, S pace EN vironment, GE ochemistry, and R anging mission) - Messenger will circle Mercury rapidly and repeatedly every twelve hours in a pole-to- pole orbit over its year-long odyssey. It will be the first new data from Mercury in more than 30 years. - visiting the Messenger website on NASA’s website http://www.nasa.gov/mission_pages/messenger/main/index.html is very useful for your own missions in that it illustrates the variety of instrumentation that a spacecraft like this will carry, what each instrument will measure, a list of questions justifying why Mercury is worth visiting, and a number of other features that will help you to structure your own missions. Dimensions Mercury is not much bigger than our moon. (Ganymede and Titan are larger, but Mercury is more massive.)
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2 - Earth is about 18 times more massive and has 18 times the volume of Mercury. A 150 lb person on Earth would weigh 57 lbs on Mercury. - they have similar densities (5.5 g/cc for Earth, 5.43 g/cc for Merc.) suggesting a
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09_Mercury - GEL36 SOLAR SYSTEM Lecture 9 Mercury(Ch 21...

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