What is the Sun? Why does the Sun shine? Is it just a ball of burning gas? To us on Earth, it is much more than that; it is an anchor and protector, a heater and source of constant energy. It is dangerous and, at the same time, life providing. It is the center of our solar system. It may prove to be the instrument of doom to our Earth.
The Sun is huge. It is the most dominant object in our solar system. About 99.8% of all the mass of our solar system is in the Sun. If one adds up all the planets, moons, asteroids, comets and dust in our system, the total would equal little more than 1% of the Sun. It is not a huge star. After all, the largest stars can be as much as 1,000 times larger than ours. But the Sun is more massive and brighter than 95% of the stars in our galaxy.
The Sun sends out lots of energy. But what kind energy does it emit? Most of it is light (photons) and infrared rays. The infrared rays are not only seen but are also felt. We call it heat. These are forms of electromagnetic radiation.
The Sun is very dangerous. Not only does it send out light, heat and radio waves, but dangerous ultraviolet rays, gamma and X rays emitted from it would kill us if it were not for the protection of our atmosphere.
The Sun is hot, so hot that it can burn our skin from 93,000,000 miles away! It is a blazing nuclear furnace. Not only is it hot, but it shoots out flames for more than two hundred thousand miles before pulling back to the Sun’s fiery surface. The Sun produces light. It creates photons that speed out beyond our solar system, even beyond our galaxy. Some of these photons have now traveled nearly 5 billion years, moving at 186,000 miles per second. Someone far out in the Universe could be just now receiving this light message. It is the story of the beginning of our solar system and of the star that rules it.
It pulls in debris that could otherwise hit circling objects. Our star keeps us from wandering away and smashing into other objects.
The Sun spins, just as other large bodies in space. It takes the star’s equator about 25 days to rotate. The upper and lower regions take about 28 earth days for a complete turn. Why? Because the object is made of gas is not a solid.
The Sun is violent. It does not have a stable surface area. Portions as big as Texas come to the surface, then cool and disappear in less than 5 minutes. Solar storms and explosions push out flames and winds that contain cosmic particles, known as solar cosmic rays that have effects for hundreds of millions of miles. The rays made up of mostly ejected protons, have some heavier nuclei and electrons. These rays can cause great harm to space travelers, probes and satellites. They cannot enter the earth’s protective atmosphere but can create a magnetic storm when colliding with the upper atmosphere. This may lead to interference or disruptions in our electrical power grids and communications.
Some more facts:
The Sun puts out a tremendous amount of power. The amount of energy the Earth alone receives is equal to 126 watts per square foot per second! That means that one weeks’ worth of solar energy landing on Earth is equal to us using all our natural reserves of gas, oil, and coal on the entire planet during the same amount of time. The difference is that the Sun will be able to do that every week for billions of years.
The average distance between the Sun and Earth is 93,000,000 miles (1AU).
It takes about 8.3 minutes for the Sunborn light to reach us at this distance.
The diameter of the Sun is 864,000 miles.
It has a surface gravity 28 times stronger than that of Earth.
More than 70 elements (atoms) can be found in the Sun. The main ingredients are hydrogen (72%) and helium (26%); the core is thought to be 38% helium.
The Sun orbits the center of our galaxy every 250 million earth years.
Our Sun is known as a “population one”, star. There are three generations of stars, “population ones” being the youngest generation. They have the highest amounts of helium and heavier elements inside them.
Dissecting Our Sun
The corona is the highest layer of the Sun’s atmosphere. It reaches out several million miles into space. It is very hot and is seen as an uneven halo around the Sun during total solar eclipses.
Next is an area that is called the transition region. It is a hot area that cannot be detected with observations during a solar eclipse. It emits light in the ultraviolet bands. It receives most of its energy from the corona.
The chromosphere is a thin, transparent layer that extends out 6,000 miles from the photosphere. One can only see it from Earth when there is a total eclipse of the Sun.
A solar eclipse means the Moon is between the Earth and the Sun. The Moon will block out all but the very outer edges of the Sun from our sight.
The photosphere is the lowest level of the atmosphere. It is about 300 miles thick and is the visible surface of the Sun. It is about 10,000 degrees Fahrenheit. The Sun has a grainy look on its photosphere. Its appearance resembles a leathery skin.
The bright areas called granules have been seen as big as 625 miles wide. They are the result of rising currents from the convection zone.
The darker surrounding areas are about 300 degrees cooler. Those dark areas are from descending gases and typically last five minutes.
The granules can be part of greater super granules that can be up to 19,000 miles in diameter. These are composed of a number of granules banding together. Super granules can last for several hours. that of water.
Nuclear reactions take place in the core, or center of the Sun, as hydrogen is converted in to helium. This is an area where the density of the star is 15 times that of lead. Here, the gas pressures are 2 million times that of the earth’s atmosphere. Fusion, (when two atomic nuclei merge.) takes place here. Nuclear matter is turned into energy. Photons are created. These are the particles that, when grouped together in a moving stream, we call light. Some are absorbed. Others escape.
The radiation zone surrounds the core. It is named the radiation zone because the energy that passes through it is mainly radiation in nature. This makes up 48 percent of the Sun’s mass. It may take a photon over 1,000,000 years to pass through this zone.
Spiricules are jets of gas that reach out as far as 6,000 miles into space and are up to 600 miles wide. Found in the chromosphere, they last anywhere from 5 to 15 minutes.
Did you know?
It is estimated that it takes up to 1 million years for a photon to escape to the Sun’s radiation zone and reach the surface. It then takes less than 9 minutes to get to Earth. That means the light you see from the Sun is about 1 million years and 9 minutes old!
Sunspots are darker areas found on the photosphere, usually found in groups of two or more, these spots can last from a few hours to a few months. They can best be seen during sunrise or sunset. Do not look for them without expert help and proper instruments! The first observations of sunspots were recorded in China around 800 BC. Galileo was the first to observe them with a telescope.
Sometimes there are no sunspots on the surface. At other times people have recorded as many as 250 of them. There seems to be a pattern of activity called the sunspot cycle. It is about 11 years from the start to end. When it is at its higher level of activity it is called the sunspot maximum.
The Sun, like earth, has a magnetic field. If taken as a whole, it is only twice as strong as the earth’s field. But, in certain areas, there are concentrations of magnetism that can be as strong as 3,000 times that of Earth. These areas are where we find sunspots. Sunspots act like super magnets. This magnetic field shows up before the spot can be seen and it lingers for a while after the spot is gone. There is a background magnetic field around the Sun. The magnetic axis is tilted at 15 degrees from true north and south.
This field is filled with energized particles created by the Sun’s rotation and gas convections. They cause outbursts of radiation and other materials.
Every 11 or so years the magnetic poles on the Sun reverse. This happens just after the sunspot activity reaches its height, thus creating a cycle of solar activity of 22 years.
Solar flares are tremendous explosions of light, radiation and particles. They can reach a height up to 200,000 miles and can produce more energy than our world can create in 100,000 years. Flares can send out 20 billion tons of matter into space during an eruption. These flares have a life span of only a few minutes. They are mostly seen when there is an abundance of sunspot activity.
Prominences are arched ionized gases that occur on the limb of the Sun. Magnetic fields and sunspots supply the energy for them. Solar winds are streams of electrically charged particles flowing out from the Sun. Unlike our wind, it is very thin, hot and extremely fast, an average speed is close to 1 million miles per hour. The solar wind takes about 4 days to travel from the Sun to the Earth. Sunspot activities affect these winds. When there are sunspots, the winds are the strongest. The winds end up somewhere beyond Neptune.
The Sun will not stay forever the same as it is now. Previously, it was mentioned that the Sun will grow dimmer. As time goes on the Sun will start running short of its main fuel, hydrogen. On the other hand, it has been developing a new fuel that will eventually power the star; helium. The Sun will someday switch over completely burning helium and will turn red in color. The temperature will drop, and the star will dramatically expand. It will then be a red giant, burning helium. The closest three planets that presently are orbiting the Sun will be actually end up within our sun! The Sun will once again change. This time it will end up as a white dwarf, burning the last of its hydrogen. During this phase it will burn off the last of its hydrogen. Eventually, the sunlight will flicker and dim. Finally it will end up being a black, burned out, cinder ball in space.
The Sun is about half way through its life cycle. It has a little less than 5 billion years of life to go. Right now it is nearly as bright as it will ever be. It is brighter now than 2 billion years ago and it is brighter than it will be 2 billion years in the future.
Asteroids : What is an asteroid? To put it simply…
it is a rock that floats through space. Sizes vary. They can be big or small and have a variety of shapes. It is thought that quite a few of these rocks are mineral – rich. They may carry rare and valuable ores. It has been estimated that there is enough mineral wealth in the Asteroid Belt, between Mars and Jupiter, to make multi billionaires of all! Much iron has been detected in some of them. Many of them are made of sandy – relatively – light silicates.
These rocks played a very important role in the formation of our solar system. In the beginning of planet formation, they often collided, melted from the heat of impact, and bonded together to form bigger hunks. Eventually they formed planetoids and then planets. Other rocks collided and became smaller planetoids which could be captured by a planet’s gravity. They fell into orbit and became what we call moons.
There are a lot of these rocks floating about. They usually fall under the gravitational influence, or pull, of bigger objects in our solar system. Many form a “belt” between two planets: Mars and Jupiter. Some scientists think that a planet might have broken up and that these pieces are the leftovers. Others believe this is simply space junk that never got to form a new planet.
These rocks perhaps may number in the billions; some are the size of sand grains, peas and softballs. Some are the size of states. Big asteroids can even have micro gravity.
Japan recently scored a major success by sending a probe named Hayabusa to rendezvous with an asteroid. (The probe is expected to return to Earth in 2010.) Hopefully it will bring samples collected from the surface of the asteroid.
The asteroid called Itokawa is 1,800 feet long by 900 feet at its widest point. Its composition seems to be silicate rock, making it a chondrite. Its orbital paths may cause it to be a dangerous object for Earth someday. Space rocks can mean much in your life. They provide entertainment with “shooting stars” and meteor showers. Or they can kill you in gigantic collisions with Earth.
An Example of Concern
may have its flight path altered as it passes us. This is called the keyhole effect. If so, seven years later, when it comes by again, it may well hit us. It is about 1,000 feet in diameter and can cause problems, but in on 69 a regional, not global, scale.
Members of NASA have proposed sending a probe in the near future to study the composition and makeup of the PHA (Potentially Hazardous Asteroid) object. Because of monetary constraints and a feeling that the chances of a hit are about twenty percent twenty three years from now, this mission will not happen in the near term.
As of now, no asteroid has been spotted that is heading for Earth.
The word “comet”, comes from the Greek word kometes, meaning long hair. This refers to the long tails that comets develop when they close in on the Sun. They wander through space, cold and dark, their jagged edges stabbing into darkness until, one day, they move ever so slightly on a new course. Their momentum increases as a strengthening force of gravity pulls them onward.
As the gravitational influence of the sun upon the comet grows, the comet’s speed increases. Eventually, the effects of solar winds and heat come upon it icy surfaces. A brilliant tail forms. The comet becomes a glorious show of light, ice, gas, and streaming particles.
Comets have long been sources of wonder and mystery to planet Earth’s human population. They were thought of as pretenders of great events, in forms of disasters. Comets were dreaded. There are written accounts of them going back over two thousand years.
Although they can be potentially “bad news” to earthlings, they are just natural objects wandering in and around our solar system.
The comets in our solar system are found on an elliptical orbit. They are attracted by the Sun and swing by it before going way out and then coming back in again. Eventually they either run into the Sun and melt, or they hit other objects, such as us!
The famous Halley’s Comet comes around every seventy years; it is like a bus on a schedule. The last time it passed by Earth was in 1986. Many of you may be alive when it passes by again. It has been tracked since the Middle Ages. Another comet, Hale-Bopp, came near to us in 1996. It is over thirty miles long and shaped like an island with mountains.
The head of the comet is called the nucleus. When it enters far enough into our solar system it develops a coma, a halo of particles flying off the comet. The particles trail behind the coma and turn into a long transparent tail. Comas have been seen to extend as far as sixty thousand miles from the surface of the comet, while tails can extend millions of miles into space. An additional feature of a comet is its hydrogen cloud. This cloud surrounds the comet but cannot been seen from Earth.
In 1950 Fred Whipple created a good analogy by describing a comet as “dirty snowballs.” Comets are made of water ice, frozen gases, stony materials and some metal solids. They are much less dense than meteors. There is some surface gravity on larger ones.
Gases coming off the comet contain the following compounds: carbon dioxide, silicates, nitrogen, hydrogen and carbon. All of these are the building blocks of life. What causes all the surface action when a comet comes close enough to the Sun? The Sun’s solar heat causes the frozen gases to defrost, and solar gravity pulls off dust. The gases and dust cannot be held by the comet’s weak gravity, so they go out into space and are captured by the same solar gravitational forces pulling the nucleus. The gases become fluorescent and the dust reflects sunlight. The comet soon becomes very visible. About twenty five of these light streaks are spotted every year.
Once ultraviolet radiation interacts with the gases, it causes the molecules to tear apart. The results are floating free radical particles known as ions. These ions mix with solar winds to form the long tails on the comets.
The ionized hydrogen gases flowing out at the front of the coma produce a bow shock. (This is when gases block the solar winds directly in front of the comet, forcing them off to the sides.)
A probe called Giotto came within 375 miles of Halley’s Comet’s head, or nucleus. It found the nucleus to be very dark, about five miles long by nine miles wide. It rotated at a speed of once every two 71 days. The surface was full of cracks, crevasses and possibly craters. From a portion of the surface gases, water vapor and dust were venting out toward the Sun. Parts of the surface looked blackened as if burned. Perhaps because of Halley’s previous passes near the Sun, frozen surface layers were either blown away or burned off.
Where do these “snow balls” come from? Many comets lie in wait in the farthest edges of our solar system in a place called the Oort Cloud. It is thought to contain as many as one trillion comets.
It was once presumed that all comets are white because of the water ice. This has been disproved. A green comet was observed in 2007 by an amateur astronomer from China. He named it Lulin. It flew by the Earth in 2009.
Why green? The comet gases, containing cyanogen and diatomic carbon, cast a green glow when light hits the particles in a vacuum, such as space.
It does not take much for these comets to start a fatal freefall toward our Sun. Imagine you in front of a comet that is ten miles wide by twenty miles long. Put out your hand and flick it with your finger. You have begun its new journey! At first the motion would not even be noticeable, but over a period of time the speed would increase and thousands of years later there would be another comet in our neighborhood.
Stars occasionally pass within a few light years of our solar system. That influence, that little gravitational change in our part of the galaxy, is enough to set in motion the movement of great mountains of ice and rock, sending these comets towards the Sun.
These comets are very dangerous to us. They are unpredictable. Many are huge. A midsized comet could virtually wipe out life on Earth. One, named Shoemaker-Levy 9, collided with Jupiter in 1994. It had been broken into fifteen chunks by Jupiter’s gravity and hit the planet with one piece after another. One such piece left a bruise on Jupiter that was the size of our planet! Undoubtedly, Jupiter has saved us many times from a collision. Jupiter, the great vacuum cleaner!
The result of another comet impact with Jupiter was witnessed in late 2009. This occurred in the area of Jupiter’s South Pole and left a mark similar to the ShoemakerLevy 9 wound on that planet.
Eventually most comets die a fiery death. We can usually find these large asteroids coming in our direction. If found in time, we might be able to do something about them, but comets are different; often they appear out of the darkness within months of being near to us. There is not enough time to prepare. Don’t let the movies fool you; we are not ready for a large comet!
Meteors and Meteorites
It is well known for its nearly perfect state of preservation.
What is a meteor? Meteors are objects that fall from space into our atmosphere. They can also be called bolides. What is a meteorite? It is a meteor that landed on the ground and did not disintegrate on impact.
Because of their speed these objects become engulfed in flames when they hit our air. They can either explode in the air or reach the ground. When they do hit, they cause devastation in proportion to: their size, what they are made of, and how high the combined speed is between Earth and the crashing objects.
Many meteorites are stony, made of silicate minerals (about 94% of all recovered rocks). Some are igneous rocks, others are mostly metal (iron meteorites) and many are a mix of both materials. Meteorites called Chondrites are composed of elements that can be traced back to the times when our solar system was being formed. Some meteors are comets ranging from the size of basketballs, (which fall onto our planet daily); to objects that are miles wide and can cause an extinction level event. (This is when much, or even all, planetary life could be destroyed by a collision).
Meteors may break up and hit the ground like a shot gun blast, or they can land in a single piece and create impact craters. These small rocks entering in our atmosphere in groups are called meteor showers. Large meteors coming through the atmosphere are accompanied by brilliant streaks of light and loud roars. When the meteorites are recovered after landing they are called falls.
When meteors hit the atmosphere they heat up and form a glass-like crust called a fusion crust. Pieces of this type of glass are commonly found near impact craters.
Meteorites have been found in many areas of the world, but most of the samples have been located in Antarctica. So far the samples found in that region represent about 3,000 different meteorites.
Near Earth Objects are mainly asteroids, but they can also be short term comets that are orbit the Earth or crossing its orbital path around the Sun.
There are two different types of asteroids and comets to look for. One type 73 are the NEOs or “Near Earth Objects”. The newest term is PHAs, or “Potentially Hazardous Asteroids”. As of January 2010, 1,086 have been found. These rocks in space can come within 4,500,000 miles of Earth and are more than 500 feet in diameter. They represent 90% of the danger in space. They are fairly easy to find. They are in our neighborhood and therefore more readily spotted. The other dangerous space objects are called intermediates and long terms. They are mostly comets. They may take years to drop by and will give us only months of warning of their arrival.
There are scientists watching for large asteroids that may cross our path. These scientists have developed an impact scale from 1 to 10, in case one of these objects does head for Earth. Zero implying virtually no damage, while a scale of 10 represents a catastrophe. The estimate is that there are at least two thousand NEOs cross our orbital highway every year. Many of them could cause the death of hundreds of thousands if they hit us. Some could kill us all.
Many of these objects have been spotted. However, there are few astronomers looking for them due to budgeting problems. Over time, we see less and less of these objects because they have already been drawn in by Earth’s gravity, or they hit the Moon, or have been absorbed by the Sun.
Every day many tons of this debris still hits the Earth’s atmosphere but is in pieces so small that they cause little concern and on occasion entertain us when see as “shooting stars”.
Near Earth Objects are mainly asteroids, but could also be short term comets that are orbiting the Earth or crossing its orbital path around the Sun.
About every 100 years, a rather large (50 yards wide), iron asteroid may hit the earth. Every few hundred thousand years an object can reach the Earth that could cause wide destruction and radical changes in planetary climate.
A famous example of a meteoric event took place in 1908 over Tunguska, Siberia, Russia. A large meteor with an estimated weight of one hundred thousand tons entered the atmosphere. It is believe that it was a comet. It exploded a few miles above the surface of the Earth. The explosion knocked down over one thousand square miles of trees. It had the force of hundreds of atom bombs.
Luckily, this part of Siberia had no human population, and the loss was limited to plants and animals. But the planetary effect was so great that it was virtually day light in London during the middle of the night, even though the blast was five thousand miles away! The sound wave from the blast circled the planet twice! Had it hit the Earth five hours earlier, the Moscow area would have been wiped out.
The largest meteor crater in the United States, found near Winslow, Arizona, is called the Barrington Crater. About three quarters of a mile across and nearly six hundred feet deep, it was caused by the impact of an iron meteorite weighing almost thirty tons.
The most famous crater is located off the Yucatan peninsula in Mexico. Called Chichlxu, it is over 150 miles wide and 74 perhaps twenty miles deep. (Remember, that is about the average thickness of the Earth’s crust.) The ejected rocks were thrown far into space. The composition of the burned rocks produced a poisonous gas. Fires throughout the Earth occurred. There was a dramatic lowering of temperature. During that time, there were no ice caps.
This collision with Earth happened about sixty five million years ago, during the Cretaceous Period, the age of the dinosaurs. No fossils of dinosaurs can be found beyond the age of this impact. All over the Earth there is a thin line of iridium found in the sixty five million year level of rocks and soil. Once this event level is located, fossils are not being found in abundance until another level representing the Earth’s surface five thousand years later.
Can this happen again? Most certainly! If a large rock or comet as big as six miles wide or more hits our planet, the devastation will be enormous. One would see earth waves hundreds of feet high. Tsunamis (Fast moving walls of water in the ocean) hundreds or even thousands of feet high, would sweep over much of any nearby coastal lands. Blazing debris from the impact would fall over the surface of the earth. The showers of rocks could be as big as a twenty story office buildings, and fires would rage planet wide. Faults would open up from the tremendous shaking and creating earthquakes. The searing heat would kill most plant life. The dense, choking smoke would soon blot out all sunlight, plunging our planet into freezing cold, with darkness so deep that eyes could be useless. Our planet grows silent and still for perhaps hundreds, or even thousands of years. No structure would be left standing. Any traces of human existence would fade until only a few fossilized foot prints and bones would tell someone in the future that we once existed. We could be the next oil deposit.
Asteroids can be charted to see if they have a chance of crossing our path far in the future. By tracking these objects, we should have years of forewarning and they have chance to use technology to change their course. We could change the velocity of the asteroid comet, but not blow into pieces creating debris that cannot be controlled. When given a warning, far in advance, of an object that may collide with earth the craft sent to intercept it will need less efforts to have the object’s speed and or course adjusted.
Meteorites can be seen in science museums and exhibits around the world. Some have been made into jewelry or pieces of art. Others have been worshiped; it is thought that the great Kaba stone in Mecca, Saudi Arabia, is a meteorite. It is located at the center in an area where millions walk in a circle as they complete their Muslim pilgrimage to Mecca.
One meteorite, discovered in 75 Antarctica, had a profound influence on mankind. When opened, researchers found what appear to be fossils of tiny animals (micro-organisms). The chemical composition of the rocks was traced back to Mars. Millions upon millions of years ago, a large meteor hit Mars. Some Martian rocks were hurled so far that not only did they make it into space, but they even escaped Mars’ gravity. Eventually some of those rocks fell to Earth.
Comet-meteors may also account for many of our oceans. The process of billions of those “dirty snow balls” entering our atmosphere has made us water and oxygen rich. Thus, these menacing objects from the sky may support life as well as take it away.
have so many moons that we may not have counted them all. Would you like to know the solar system moon count as of 2010? The tally is up to 167 and counting.
There are different types of moon – satellites. The size and roundness of them vary. Most are formed near their partner planet. Some are asteroids that were captured by a planet’s gravity.
Here are some terms that are used in the moon exploration business that concerns how moons orbit their planets:
Inclination: Describes the orbital path of the satellite compared to the equatorial latitude of the planet.
Prograde: Is orbiting the planet in the way that a planet orbits the Sun while it is circling between 0 and 90 degrees compared to the planet’s equator. The vast majority of moons are prograded. They circle counter clockwise if looking down at the planet’s north pole.
Retrograde: Is orbiting the opposite direction of the way planet travels around the sun and/or has an orbital path that is more than a 90 degree angle than the equator. Most, if not all retrograde moons are captured asteroids.
Irregular: Moons that have elliptical orbits and are still within the 90 degree equatorial angle.
Regular: moons are all prograde, but not all prograde moons are regular. Some are irregular.
All prograde – irregular moons have an “a” at the end of their names. All retrograde moons have names that end in the letter “e”.
In this section, we will look at some of the more interesting moons, which include our own.
We see our moon at night – sometimes even by day. It is big, round and looks a little beat up. The colors are whitish gray, gray and some black. It can also be yellow when close to the horizon and very bright and white when high in the sky.
Our Moon had different names during ancient times when many thought of it as a goddess. Some of the given names were: Diana, Lunea, Cynthia, and Selene. It has been both worshipped and feared. It was an object representing romance. It was a light for harvesting at night. It was thought of as a factor in transforming people into werewolves. It was believed that the Moon could even cause people to become “lunatics.” (Derived from the Latin word luna.)
We have only one moon. In English, we call it the Moon. It is one of many in the solar system. Here are some of additional Moon facts: It has a 2,160 mile diameter at its equator.
The Moon is a little more than one quarter the size of Earth.
Its density is about sixty percent of the density of the Earth.
Its average distance is about 221,423 miles from Earth. Its orbit is elliptical (an oval shaped path). The farthest point the Moon is from Earth is 252,667 miles.
There are tremendous temperature swings on the Moon because there is a very slight atmosphere to hold or release heat and cold.
The Moon travels around the Earth at a rate of nearly 1.5 miles per second!
There is water ice on the Moon.
Evolutionists age the Moon at 4.4 billion years.
It has 17% percent of earth’s gravity.
Have you ever noticed that there can be a “halo” around the Moon? It is not what it seems to be and neither is it where it seems to be. The circle is caused by ice crystals high in our sky.
Another phenomenon is known as the “Moon Illusion.” No one is quite sure why, but the Moon looks much bigger when seen at the horizon level.
The Moon has structure. The center, or core, is thought to be solid but could be partly molten. Moonquakes have been detected. They are very weak, leading to the belief that there might be some liquid towards the middle of the core. Moonquakes seem to be related to the tidal forces caused by interacting with Earth’s gravitational forces.
The surface temperature averages 107 degrees Celsius in the sunlight and -135 degrees Celsius in the shadows. Sometimes the temperature drops as low as -249 degrees Celsius, which would rival temperatures found in the Kuiper belt.
Galileo thought that the dark areas on the Moon were oceans. He called them maria, (plural), or mare, (singular). The mare is actually basalt rock lava beds that have cooled from the pouring out of magma, were caused by meteorite impacts cracking the surface. The largest mare is the Mare Imbrium, 1,700 miles across.
The highest areas on the moon are known as “The Highlands” and are some of the oldest surfaces on our Moon formed, during the period of volcanism. As the Moon cooled, there were flows of volcanic basalt, which were most active between 3.2 and 1.2 billion years ago. Igneous (volcanic), rock areas covers almost 80% of the Moon’s surface. Some smaller features exhibit geographical features that appear to be caused by out – gassing. (An explosive leakage from subsurface gas pockets.)
Virtually all of the Moon’s mountains are walls of craters. Very few high hills or mountains are from volcanic episodes, since the Moon has no tectonic plates; no mountains were caused by plate movement.
The Moon is mostly covered with silicon dioxide, magnesium, calcium, glass and dust, which form a layer called the lunar regolith, ranging in depth from 5 to 50 feet. It is created by the smashing of the surface that result in debris from the impacts of meteorites and micrometeorites being strewn over the surface. When brought back to earth and studied, scientists said it had the scent of gunpowder.
The crust is made of 45% oxygen, 21% silicon, 6% magnesium, 13% iron, 8% calcium and 7% aluminum. The mantle: underneath is made up of olivine, orthopyroxen and clinopyroxen. The core of the Moon is only 255 miles in diameter and seems to be made of partly molten iron and nickel. Some of the basalts on the surface also contain titanium.
The Moon is the second least dense moon in the solar system. (Only Io is less dense.) The Moon has a magnetic field that is much less potent than the one form emanating from Earth.
The moon looks a little beat up! In a way it is just that. It has small craters called craterlets, larger craters, some extremely large craters more than a hundred miles across, called “walled plains”. Most of these craters were the result of meteor hits. The larger pieces of material ejected by these collisions caused more craters to be formed. Smaller particles blasted out, called “rays”, formed patterns that stretch out for hundreds of kilometers.
The far side of the moon looks far different from that facing the earth. It does not have large maria, but it does have craters and highlands.
The Moon, (La “Luna” in Spanish), is being hit constantly by space debris. With no atmosphere to protect it, the surface is bombarded by large as well as sand-sized rocks, small meteors called “micrometeorites” they hit the moon at speeds up to 70,000 miles per hour. This makes the moon’s surface a very dangerous place for humans. A small grain could go right through the body of an exploring astronaut!
The micrometeorites affect changes on the surface of the moon: they can cause erosion. However, they are 10,000 times less effective in creating changes than those caused by air and water on the surface of our Earth.
Several years ago a military satellite turning toward the Moon to adjust its instruments, reported back an amazing find: water ice on the Moon! NASA sent a probe, called a “Lunar Prospector”, to investigate and to confirm the findings. It is now thought that ice could have come from comets that have collided with the Moon. The spacecraft Clementine has further confirmed these phenomena. The Indian probe, Chandrayaan, detected large quantities of ice.
The ice is not only in permanently shadowed craters, but it may also be found in the regolith. It seems there are literally millions of tons of ice present. One 10th of 1% of the regolith soil may be frozen water. Scientists looked again at the collected Moon rocks brought to earth by the Apollo 15 astronauts and found that there was water in some of them.
This ice could be used to support a space station on the Moon. The hydrogen and oxygen can be separated, and the elements used for drinking water, breathable air and rocket fuel.
The Moon’s atmosphere is extremely thin but has a very complicated composition. It most likely results from decay and out – gassing. These elements are: sodium, potassium, polonium, argon, oxygen, methane, nitrogen, carbon monoxide and carbon dioxide.
We have sent many “visitors” to our moon, including machine probes and manned vehicles. Later in this book, we will study these explorations.
There have been several recent discoveries, most of which were found by the lunar astronauts who brought back moon rocks. The rocks range in age from 3.1 billion years to 4.4 billion years. The rocks also reveal another important fact: The Moon has a different geologic make up than present day Earth.
The Moon has several measurable effects on Earth. One is that of the lunar eclipse. That’s when the Moon passes between the Sun and the Earth. The shadow of the Moon falls upon the Earth. From Earth, the Sun and Moon look the same size because the Moon blots out the sunlight when aligned with us.
A major Moon influence on Earth is the tidal effect. The Moon’s gravity actually pulls at our oceans. The powerful pull of our natural satellite can change the depth of the coastal waters by many feet in a few hours. (This subject is covered in the Planets / Earth section.)
Where did the Moon come from? How did it form?
There are several theories:
The Fission Hypothesis: The Moon was formed by a chunk of partly molten earth flying off into space and leaving the Pacific Ocean area as a scar.
Capture Hypothesis: The Moon was a free – wandering space object that was capture by our planet’s gravity.
Co-formation Hypothesis: The earth and Moon formed at the same time.
Giant Impact Hypothesis: A large object, perhaps a large as 1/3 of the earth, collided with our very young planet and debris was thrown into space. This debris coalesced into the Moon. This is presently, the most popular scientific theory.
Where is the Moon going? It is currently drifting away from Earth at 1 ½ inches, per year. Theoretically, over billions of years, the Moon could become a planet. But the Moon and Earth, according to science timelines, would already be destroyed by the Sun.
Did you know?
When seen on Earth, the Moon is 25,000 times brighter than the nearest star, other than our Sun. But it only reflects 11% of the sunlight shown on it.
The Moon has a synchronized rotation. A moon day rotation equals the same amount of time it takes the Moon to go around the Earth (27.3 days). Therefore, we can only see one side of the Moon at any given time.
This, the largest moon in our solar system, is also the seventh largest world as well. Titan was discovered in 1655 by Christiaan Huygens. It is the most complicated moon when considering its atmosphere and its interactions within the moon’s surface.
Larger than Pluto and Mercury, Titan is one of the 22 moons of Saturn. It is famous not only for its size but also for its atmosphere. Titan is the only moon with a substantial atmosphere. Other than our own Moon, it is now one of the most studied moons in the solar system. The largest moon in the Saturn system, it orbits Saturn from a distance of about 720,000 miles. It takes 16 earth days to circle Saturn.
Its atmosphere contains 95% nitrogen and 5% methane, plus a multitude of trace gases. Its surface air pressure is actually 50% stronger than that of Earth’s atmosphere. However, differences between temperatures of Titan and Earth are extreme. The average temperature of Titan is -292 Fahrenheit. Methane freezes just a few degrees below that level. Methane, on Titan, is found in frozen, gaseous and solid states. The atmosphere averages 190 miles in thickness. There are continuous strong winds in the upper atmosphere that are as fast as category 3 hurricanes. These winds make the atmosphere move around Titan five times faster than the spin of the moon itself. Its lower atmosphere tends to be calm.
It rains ethane on Titan, in very large drops (1cm). The rain drops to the ground, just like it does on earth. But because there is much less gravity, it can take as much as an hour for them to finally land. Most of the drops evaporate before they reach the ground.
From a distance one cannot see any features on Titan. It is covered with a yellowish brown -thick- haze of methane, ethane, and acetylene compounds. It actually snows on this moon! The snowflakes are made of methane and fall slowly to the ground, due to the light gravity of this world. Every day appears to be gloomy on Titan.
The sky is brown and the sunlight gives little more illumination than our moonlight provides. A day on Titan is 16 Earth days long. Eight are dark and, the rest are gloomily lit.
Did you know?
During the recent fly – by of Titan, by the space probe Cassini, it recorded radar images of lakes! They are filled with liquid hydrocarbons. This makes Titan the only place, other than Earth, that is known to have liquid lakes! Many of the lakes look like they may be filled in impact craters or are a result of volcanism. Others look like a typical filled – in lake on earth. Does this mean there is an equivalent to Earth’s water cycle working on Titan? Time will tell. Saturn takes 29 years to orbit the sun. As observations continue, we will be able to tell whether there is seasonality to these liquid deposits.
Iapetus is the third largest moon in the Saturn system. It is a peculiar world that is very bright on one side, very dark on the other. (One side is ten times brighter than the other side).
Iapetus is the third largest moon that orbits Saturn. It orbits at a distance of about 2.1 million miles from the planet. It takes 79.33 days to complete one orbit.
The light side looks like a typical cratered moon. The other side is as dark as charcoal and has virtually no features. The darkness may have to do with collecting dust from the moon Phoebe or maybe that part of the moon is more exposed to the sun and the ice has melted. The Cassini space probe arrived in 2004 tried to investigate why this situation exists. So far, there are no conclusions. Iapetus has polar water ice. It also has frozen carbon dioxide lying on its surface. This moon is a little less than half the size of our Moon.
Iapetus has a clearly defined equator and is marked by a mountain line around the middle. From a distance, this feature gives the moon a glued together look.
There are other moons that orbit Saturn. Mimas looks like a typical battered moon. Mimas, Rheas, Enceladus, Dione, and Tethys are midsized moons. These worlds, as well as the smaller moons, are airless and icy .
Ariel is nearly all ice. Not only is the surface icy, but so is the interior. It has strange canyons in several areas. Probably it was partially melted in its early years. This moon is about one third the size of our own.
Triton, a moon of Neptune, is a very cold place that averages – 400 Fahrenheit during the day or night. The surface water ice is as hard as granite. There may be liquid nitrogen pools lying below the surface. This type of “ground water” is heated by decaying, radioactive particles and tidal forces from nearby Neptune.
Occasionally the liquid breaks through, and geysers shoot it above the surface. As it falls, it freezes and forms snow on the surface. Methane mixed with liquid falls nearby, leaving purple and black stains near the vents. In essence these vents act as ice volcanoes.
Triton has an interesting and fairly unique feature; it has wind. The air is thin and clear. Sometimes a thin cloud can be seen. The atmosphere is fed by geysers.
Did you know?
There is a theory that a planet near Triton was once orbiting the Sun and was captured by Neptune’s gravity. One reason for this theory is that Triton orbits around Neptune in the opposite direction of the planet’s spin. (Saturn has one moon which does this and Jupiter has four.).
This is a world that is so different from the rest of the solar moons. It is a moon of constant change. A violent place, it has extraordinary events happening daily.
Io is the 13th largest space object in the solar system. Discovered by Galileo 63 Galilei, it is close to 30% the size of earth. It flies around Jupiter, making one orbit every 1.8 days! It circles Jupiter at a distance of a little more than 250,000 miles.
When Voyager 1 passed Jupiter in 1979, the cameras turned to it and captured one of the most stunning images ever taken. It was a moon with not one visible meteor crater. The place is orange, yellow, white and brown with touches of black. Some say it looks more like a giant pizza.
After several days of investigation the team of scientist realized they were looking at a moon with many active volcanoes. There are at least 300 hundred of them. These were the first active volcanoes ever seen outside of Earth. It has incredible volcanic lava temperatures that range from 1,400 to 1,700 degrees Fahrenheit. Most likely the magma contains a lot of magnesium, which tends to burn hot. The lava on Io is hotter than the lava on Earth. The vents shoot out both liquid rock and gaseous sulfur. Jets of gas and molten rock spout up as much as two hundred miles above the surface. There are even lakes of liquid sulfur and rivers of molten lava. This moon is the second hottest place in the solar system, second only to the Sun.
Most of Io’s interior is molten. The surface is a weak, brittle and has a thin crust over a hot ball of molten sulfur dioxide. No other moon is like this one. In fact, no other moon even comes close. The gravitational forces of Jupiter and three other moons pull and mix Io into this weird state and make the moon have an elliptical orbit. It is estimated that the side of Io that faces Jupiter can be pulled out into space for as far as 6 miles.
The volcanic activity is so widespread and constant that it is useless to try to map this moon, in 5 to 7 years the whole surface may look different. Every billion or so years the whole moon turns itself completely inside out!
Where the volcanoes are not spewing, there is ice and cold rock. The average temperature on Io’s surface, away from the vents, is -143 degrees Fahrenheit. Magma and ice; Io is a moon of contradictions.
Ice and cold are not the only interesting observation one can make about this world. When pictures of this moon were studied it was easy to compare the surface of Europa with glaciers on our own planet. The folds, crevasses and undulations look the same. It has 70% sunshine reflectivity off the icy surface, making it very visible in the sky. (Remember, our Moon has only 11% reflectivity.).
It’s about 2,000 miles in diameter and orbits Jupiter from a distance of 400,000 miles. Europa takes only 3.6 earth days to orbit its planet.
The icy surface area is estimated to be, on average, 30 million years old. There are some craters, grooves and cracks on its’ surface. The average temperature at the equator is – 260 degrees Fahrenheit. At the poles, the temperature drops to -370 degrees. This was caused by the underlying liquid and possibly tidal forces when it passes near other moons.
There is a very slight atmosphere around Europa. The air is composed of oxygen. When charged particles from the sun hits the surface interacts with water molecules, thereby releasing some oxygen and hydrogen occurs. The hydrogen is lighter and therefore escapes more easily from the moon’s grip.
But what is under all that ice? To quote a line from the movie 2010 it might be: “Something wonderful.” The ice is anywhere from 10 to 100 miles thick. It replenishes itself on a continuing basis. In many ways it acts like our atmosphere; it retains heat, provides protection from cosmic projectiles and blocks out dangerous rays from penetrating the outside, protective layer.
Beneath this ice cover is a sea up to 60 miles deep. It is made up of water. The core is hot rock. Could there be life in this sea? The answer is absolutely… yes! The icy surface on Europa could very well have been liquid when Jupiter and Europa were young. Primeval life may have formed in its oceans and may still be there, under the ice. This likely would be aquatic life with no knowledge of the Universe above the ice, which is not much different from the deep sea life that never breaks the surface of our own oceans. It very well could be that our first alien contact will be with creatures living on a moon circling Jupiter. Today, there may be alien life form near a hot vent of the ore, feeding and may be able to think: “What’s up there?”
There are plans to launch a spacecraft to with lasers and radars to study its’ surface. This would provide additional information about subsurface conditions. It is the next step towards having a probe land on the moon and drill, or melt, the ice in order to see if organisms dwell below the surface.
Ganymede, the largest of Jupiter’s moons and the largest moon in the Solar System, bigger than Mercury, is pocked by many impacts. The moon is mostly composed of ice, with dust and dirt lying about on its surface. The Moon’s has a skin of dirty ice and when objects hit it, they expose a clean ice sheet beneath. The materials from the collisions are thrown out onto the surrounding area, providing some contrast between clean ice and the dirty ice surface. There are many craters on the moon, suggesting that its surface is very old. The ice, over time, reduces the craters by relaxing the walls leaving more rounded edges and eventually flattened – circular scars on the surface. These are called palimpsets.
Ganymede had internal heat at some point. How much is not clear, but there can been seen some effects on the ice. This may be the reason that it has its own magnetic field.
Like Europa, it too probably might have a below – surface, saltwater sea. But the ice on this moon is much thicker than that found on Europa. The core seems to be made of metals and rock.
The outermost of the Galilean, (Jupiter’s) moons, Callisto has been peppered with debris. It is one of the more cratered worlds in our solar system. It is covered in water and carbon dioxide ice. This probably means that its surface and the object itself are very old. The relaxing of crater walls has occurred, as happened on Ganymede.
Our Moon and Callisto resemble each other but with a major difference; Callisto is mostly of water! They have the same strength in gravity and have no atmospheres, but a rock sampling from Callisto would melt at room temperature. The moon consists of a mixture of water ice and dirt. The ice thickness of the moon is several miles deeper than on Europa or Ganymede, making the possible liquid water below the crust impossible to reach.
The surface temperature on Callisto is around -230 Fahrenheit. It is the second largest moon of Jupiter and the 12th largest space object in the solar system. It orbits Jupiter from a distance of 1.2 million miles and completes one orbit of Jupiter in a little over 16.5 earth days. The core is most likely rock, the rest perhaps water ice, slush and liquid salt water.
This moon of Saturn has an orbit distance of 7.5 million miles. The 9th largest moon in Saturn’s system, it is a captured asteroid that has a retrograde orbit. One trip around Saturn takes 550 earth days. This asteroid turned- moon is pockmarked by craters. It has a water and carbon dioxide – ice, covering.
Enceladus is the most reflective of all the moons. About 99% of the sunlight reflects from its surface. It is also the smallest moon with an atmosphere. It has water geysers that provide the inconsistent atmosphere and replenishes a smooth looking surface. The energy producing these actions could be tidal in nature coming from Saturn and a few nearby moons.
The average surface temperature is – 330 degrees Fahrenheit. There are less than 20 smaller craters to be found on the moon.