Our Favorite Little Satellite It’s pretty, but how did it get there? The MoonBy Moira Whitehouse PhD http://www.areavoices.com/ photo courtesy of Bob King
The currently accepted theory for theformation of the Moon is called the “GiantImpact” theory. It states that about 4.5 billion years ago, just a few million years after Earth had formed, a large body (about the size of Mars) smashed into Earth.
As a result, a gusher of molten hot material wasejected into space as a cloud of debris which fellinto an orbitaround Earth. This debris came primarily from the Earth’s mantle. Due to Earth’s gravity, most of theNASA heavier material in this cloud eventually fell back to Earth, while lighter material remained in orbit around Earth becoming the Moon.
Evidence for this idea is found in the rocksthat NASA astronauts have brought backmany moon rocks. The composition of theserocks is similar to Earth rocks. Most of these rocks were formed between 3.8 and 4.1 billion years
Although it looks small up there in the sky, themoon is apretty largehunk ofrock. Thediameter ofthe Moon isabout ¼ thediameter ofthe Earth, but Wikipedia commonsbecause it is made from lighter stuff, it is only1/6 of Earth’s mass.
Because the Moon’s mass is less , its gravity isalso less than Earth’s—about one-sixth asmuch.Since weight If this mandepends on weighed 240 lbs ongravity, Earth, heeverything on wouldthe Moon would weigh onlyweigh about 40 lbs onone-sixth as the Moon.much as it doeson Earth.
Also, everything you lifted would be muchlighter on the Moon that it would be onEarth. However, its mass (the amount ofmatter in it) would not change.
Astronaut Alan Shepard struck two golf ballswith a golf club on the Moon, driving them, ashe jokingly put it, "miles and miles and miles."
Because it has less gravity, astronautsmade some fantastic jumps on the Moon.
Although the Moon’s gravity is less than Earths, itsgravity is strong enough to affect us. Everything ispulled by the Moon’s gravity, but the only thingnoticeably affected is water in the oceans. Thetides occur because of this gravity’s affect on theplanet. Interestingly,scientists think that it isalso because of the tidaleffect that the Moon isslowly drifting furtheraway from the Earth ata current rate of 4 cm/yr.
As interesting as gravity on the Moon is, therole gravity plays in relationship between theSun, Earth and Moon is even more so.It is gravity that keeps the Earth orbiting(revolving around) the Sun, the Moon orbiting Earth’s axisthe Earth. Moon orbits the Earth Earth orbits the Sun
As it orbits the Earth (once every 29.5 days), the Moon is also rotating on its axis, (once every 29.5 days).Like the Earth theMoon rotates on itsaxis except muchslower, once a day forEarth verses about oncea month for the Moon. NASA
Because the Moon makes one revolution inexactly the time it takes to make one orbit of theEarth, the same side of the moon always pointstoward the Earth. From Earth, therefore, wesee only one, always the same, side of theMoon. The other side faces away from Earthand is often called the dark side of the moon.A more accurate term to describe the side ofthe moon we see is the near side and oppositeside as the far side. The near side will alwaysface toward the Earth, and the far side will alwaysface away.
Also because the Moon is rotating (although veryslowly), each side, at some point, faces the Sun andat some point, away from the Sun. So the Moonhas a day side and a night side, just like the Earth.But on the Moon thedays and the nights lastabout half a montheach. The parts of theMoon we can see are. “day” parts of thethenear side, the “night”parts are dark and thefar side is not visible from Earth.
To help visualize the idea that we alwayssee the same side of the moon, imaginethat you are an astronaut who was landedin the middle of the near side of the Moonand had to stay there for one monthbefore you could be picked up. As the Moon slowly rotates while orbiting the Earth, you remain in the center of the near http://www.areavoices.com/ graphic courtesy of Bob King side nearest Earth.
Thinking about being on the Moon…The following should interest future astronauts: Water on the Moon? Atmosphere on the Moon? The Moon’s structure and topography?
Scientists are not sure that there is water on the moon. Recent explorations landed a lunar Water??? probe near the Moon’s north pole looking for evidence of water. There apparently was some evidence ofSouth pole of Moon water in the form of ice.
The Moon has virtually no atmosphere.Therefore, there is no weather on the Moon,no storms, no rain, no wind, no snow, but Atmosphere???the temperature can fluxuate wildly.The temperature on the Moon ranges fromdaytime highs of about 130°C = 265°F tonighttime lows of about -110°C = -170°F
The fact that the Moon has little or noatmosphere affects other things on the Moon.For example, there is no wind or water causedweathering, erosion or deposition on theMoon. Things do not erode.This footprint would look the same today as itdid 30 years ago.
The lack of atmosphere also affects sound aswe know it. For sound to travel, there must bea medium for the waves to travel through.On Earth that would usually be air or water. On the Moon, there is no air, so soundcannot travel above the surface.When the Apollo astronauts were out on theMoons surface, they could only talk to eachother, and to mission control, by using theradios in their air filled helmets.
When the astronaut in the photo hit themoon’s surface with this shovel, nosound was made.
Another result of no atmosphere on the Moon:Even during the day time the sky looks black becausethe atmosphere is not there to scatter sunlight.
The moon was formed about 4.5 billion of yearsago. Most of the structures we see today, themaria and the highlands, were formed between3.0 and 3.9 billion years ago. Structure???During that time, the Moon was bombarded bymeteorites, comets and asteroids. Some ofthem were very large and created large impactbasins.The crust of the Moon was cracked in some placesby this bombardment and magma from the interiorflowed out on to the surface filling these impactbasins.
Earth was also bombarded by objectsfrom space. However we see only a fewmeteorite craters because most objectsburned up during entry due to frictionwith Earth’s atmosphere. The craterscreated by objects that did actually hitthe surface have been eroded away bywind, rain, and other forces.There are, however, many craters on the Moonsince it has no atmosphere to burn up themeteorites on entry and since there is no windor rain to erode the impact craters away.
No volcanoes, no fold or no fault mountainsare found on the Moon.The Moon does have “moonquakes”.Almost all moonquakes are smaller thanEarth’s constant grumblings and are notcaused by plate movement.
Seeking information on Moonquakes,Astronaut Buzz Aldrin deploys aseismometer in the Sea of Tranquility.
There are several mountains and mountainranges on the Moon.These mountains are almost always found onthe rims of large craters formed by impacts byobjects in space.Several lunar mountains are well over 10,000feet tall.The Moon does not have jagged mountains,instead the Moons mountains are round andsmooth.
Moon mountain in foreground, the Sunand planets in background. http://www.areavoices.com/ photo courtesy of Bob King
The prominent Sculptured Hills werephotographed by astronauts Schmitt and Cermanon Apollo 17. Although these hills are quiteimpressive, the highest mountains on the moonare 15,000 to 20,000 feet high.
The never ending bombardment of the Moon hascontinuously fractured and sandblasted the rock Astronaut Harrison Schmitt collecting rocks from the Moon during the Apollo XVII mission.surface creating a layer of loose “soil” made up ofdust and broken rock called the regolith. The uppermost part of the regolith is mostly fine, glassy, slippery dust. This lunar regolith covers Regolith the Moon from a depth of a few meters on the mare, to a few tens of meters on the highlands.
What is it like on the Moon?On a clear night of moon observing, onecan see that there are two types oftopography on the Moon’s surface—thedark colored regions called the maria andthe light-colored highlands that surroundthe maria.
Photo Mare of the near side of the Moon Highlandshttp://sos.noaa.gov/
The flat, dark colored, smooth areas that were created appeared from Earth like “seas”.They were named maria (Mare, singular),which means seas because earlyastronomers thought they were Mariafilled with water.They are now smooth, flatplains with little evidence oftheir earlier bombardment.The dark material filling the Maria isactually dark, solidified lava from http://starchild.gsfc.nasa.gov/that earlier period of induced Lunar volcanism.
After the earlier period of maxiummariaformation, the surface of the Moon has notchanged very much.There are some moonquakes which causeoccasional landslides.The daily heating and cooling of rocksbreaks up the rock but at a very slow rate.But the main on-going geological activity iscontinuing meteoritic impacts but at a muchmuch much slower rate than in the heavybombardment in the early history of theMoon.
Maria on the near side of the MoonWikipedia Commons
The highlands are hilly and heavily cratered and cover about 80% of the total lunar surface. HighlandsThe far side of the Moon is made up almostentirely of highlands with many many cratersand very few of the dark smooth basinscalled maria.
Here we have black and whitephotos of both sides of the Moon.
The same photos artificially colored, give us a goodidea of surface elevations on the moon.
While looking closely at the Moon, you see circles of varying circumferences, which are the craters. Most craters have a circular outline; a few are more elliptical shapes.There may be as many as 200,000 craters, mostof them quite small, on the Moons surface.
A crater consists of a thin elevated ring forming its perimeter.The surface within the ring is a bit belowthe surrounding edge and in the centerthere is often a peak.
What causes the Moons phases?The Moon goes through phases (the view seenfrom Earth at various times in the Moon cycle)because: 1) the Moon is revolving around the Earth, 2) the Moon is reflecting sunlight towards the Earth.Half of the Moon is always in sunlight, half if itis dark: however, we can see only the litportion which, depending on it’s position inthe orbit, usually gives us a view of only partof the Moon.
Although it is really a continuous andgradual change, there are eightrecognized phases that the moon goesthrough and they always occur in thesame order.In this repeating pattern the Suns lightmoves, in our view, from right to leftacross the surface of the Moon.
As shown in the diagram, the new moonoccurs when the moon is positionedbetween the earth and sun. The entireilluminated(lit up) side ofthe moon is onthe back partof themoon–the half thatwe cannot see. http://www.wiseg orilla.com
At a full moon, the earth, moon, and sun arein approximately lined up, just as the newmoon, but this time the moon is on theopposite side of theearth. As a result,the entire sunlitpart of the moonis facing us. Theshadowed portionis entirely hiddenfrom view. http://www.wise gorilla.com
The first quarter and third quarter moons(both often called a "half moon"), occur whenthe moon is at a 90 degree angle with respectto the Earthand Sun. So we areseeing exactly halfof the Moonilluminated andhalf in shadow. http://www.wise gorilla.com
Although wegive names tocertain phases,each night thechange isactuallygradual.
Select Moon Phases in the following URLfor an outstanding animation of the Moonand its phases. Select “Moon Phases” http://www.valdosta.edu/~cbarnbau/astro_de mos/frameset_moon.html
Let’s look at the phases of the moon on acalendar for November, 2009. Notice thatthe change from phase to phase is verygradual and takes about a month for thecycle. http://www.tutiempo.net/en/moon/
It takes about one month, 29.5 days,for the Moon to orbit the Earth.Which, of course, is also the timefrom one new moon to the next.
Buddhist ProverbThree things that cannot long be hidden:the sun, the moon and the truth.