by Peter Jekel
Here men from the planet Earth first set foot upon the Moon. July 1969 AD. We came in peace for all mankind.
~Neil Armstrong
The Moon sits there in the night sky and sometimes even the day sky, but we often take no notice. It has always been there like a comforting beacon. Its closeness to us at approximately a quarter of a million miles and the intensity of the sunlight bouncing off of it make it appear as the second brightest object in the sky.
The Moon is our closest interplanetary neighbor. It is also our only natural satellite and the largest known satellite relative to its planet. It has been worshiped as a god or goddess by cultures going back into antiquity. It also is the only world other than our own where humans have actually walked, driven and even played golf.
What would you say if it disappeared, though? Would you notice any changes? The short answer is “yes.” Initially you would think the biggest change would be that the night sky would be a lot darker -- which is true. However, there is more. Without the Moon, our Earth would probably be quite alien to us. In fact, if the Moon was not where it is today, we probably would not even be here. Jack McDevitt speculated on the Moon disappearing from our sky in Moonfall, a novel in which the Moon is on collision course with a comet just as a new lunar base is being opened.
One fact that most people know about is that the gravitational tug of the Moon causes the tides here on Earth. We can see these effects on our Earth when we observe the tides along our coastlines with the highest tides on Earth happening in Canada’s Bay of Fundy, where the water rises and falls up to fifty feet twice a day. Tides are more than a tourist attraction, however.
Tides happen because of the gravitational pull between two bodies. Gravity is inversely related to the square of the distance the two objects are apart. When the gravitational attraction between two objects differs, as it does in the Earth-Moon system, there is a stretching along the axis of the two objects creating a tidal force. With liquid water, as we have here on Earth, the tidal forces cause water to bulge, thus creating the tidal effects that we can see.
These tidal effects are important for more than that in that they have a stabilizing effect on the planet Earth. Were it not for these effects of the Moon, the world would be a very different place. The early Earth has been estimated to have turned on its axis every four hours. As a result, winds would have been far greater, possibly too great for life to arise on land. In addition, higher wind velocities may have further restricted the mixing of warm and cold air on our Earth, creating bands of extreme temperature variations. Tidal effects slowed the Earth’s rotation to the twenty-four hour day that we have today.
As the Moon stabilizes the Earth by the tidal interaction between the two worlds, those same tidal effects are causing the Moon itself to slowly spiral away from us at a rate of about two inches per year. This concept was first proposed by the son of Charles Darwin in 1887, George, and proven with instrumentation placed on the Moon by Apollo 12 astronauts.
At least one science fiction author has looked at the possibility of the Moon moving closer to the Earth. Life as We Knew It, by Susan Pfeffer is about an asteroid that collides with the Moon with such power that the Moon is knocked closer to the Earth.
Does the presence of tides have any other significance for us back here on Earth? Many evolutionary theorists believe that early life on Earth was able to gain a foothold on land with the tidal pools being an intermediary stage. Without the presence of tidal pools providing a transitional landscape between water and land, life on land may never have arisen.
Fortunately for us, around four and half billion years ago our Moon did indeed form. There are several hypotheses as to how this happened. One was the gravitational capture of the Moon by the Earth. This theory was the basis of James Hogan’s Inherit the Stars. In the story, the Moon is found to have once orbited the fictional planet Minerva which exploded around fifty thousand years ago to form the asteroid belt. However, the weakness of the hypothesis is that the Earth would have required a hugely extended atmosphere to dissipate the energy of the passing Moon. Another theory suggested that the Moon and Earth formed together; however, its weakness is that it does not account for the lesser amount of the metallic iron in the Moon. Another theory is that the Moon was flung out from Earth by centrifugal force. However this would require an unrealistically high spin of the Earth to happen.
The strongest candidate for the Moon’s origin is that it formed as a result of an impact here on Earth: through destruction comes life. A Mars-sized object named Theia collided with the early Earth blasting material into orbit around it, which eventually collapsed into the Moon. Computer simulation models show that this theory would be consistent with the angular momentum of the Earth-Moon system (a weakness in the other origin theories).
We know that the Moon is not made of cheese as was first suggested in 1546 by John Heywood’s Proverbes which coined the phrase “The moon is made of a greene cheese.” “Greene” means that the cheese is aged, not green from rot. In addition, not only is the Moon not made of green cheese but it is made of the very essence of the birthing planet, Earth. In effect, the Moon was created out of material from the Earth and not Theia. The oxygen tungsten isotopic compositions of Earth and the Moon are almost identical whereas in other worlds of other solar system bodies such as Mars and the asteroids the ratio is far different.
The Moon has a distinct crust about fifty km thick, a 1330 km mantle, a partially melted inner mantle about 150 kilometers thick, a fluid outer core and a solid inner core. On the surface of the Moon we have areas that were once thought to be seas of water, called maria. They are actually vast pools of solidified basaltic lava and are found on the near side of the Moon in a ratio far different from the far side respectively thirty to two percent. Unlike basalt on Earth, the basalt on the Moon contains higher levels of iron, probably due to the lack of interaction with water.
Lighter areas of the Moon are called terrae or more commonly the lunar highlands. Unlike mountains on Earth, they are not the result of tectonic events but rather plagioclase culminates (minerals of the feldspar family) of the lunar magma ocean.
Within the terrae and maria, there are breccias which are fragments of rocks welded together by the heat generated by meteor impacts. Though found in maria, they are more common in the highlands.
The most distinctive feature on the Moon is its impact craters. The craters are a true indicator of what a shooting gallery we find ourselves in with respect to the universe. They are formed when the lunar surface is hit by an asteroid, meteor or comet. Without any weather the imprints on the Moon last a very long time. Estimates today suggest that there are over three hundred thousand impact craters larger than a kilometer in diameter on the Moon. With Earth being that much larger a target for space debris, we can only imagine the violence that our planet has seen in its past. Some of the craters on the Moon are even larger, ranging up to hundreds of kilometers in diameter. These impacts were so powerful that they are often accompanied by multiple rings of uplifted material.
In addition to craters, there are geological features known as rilles. Precise formation mechanisms of rilles have yet to be determined. Rilles probably have many different origins ranging from lava channels, near-surface dike intrusion, collapsed lava tubes, subsidence of lava-covered basins and even tectonics.
The lunar surface itself is covered by a dust called regolith which is pulverized material formed by impact processes. Until the landing of the first probe, the Soviet Union’s Luna 2 in September 1959, on the surface of the Moon, it was believed by some scientists that the moon dust would actually envelope anything landing on it. One science fiction author also speculated on this possibility. In his A Fall of Moondust written in 1961, Arthur C. Clarke describes a lunar dust boat full of tourists sinking into a sea of lunar dust. A possible reason for the lag of two years between the science of moondust and Clarke’s story could have been due to the secretiveness of the Soviet space missions as well as delays between writing and publishing.
Believe it or not there is water on the Moon which bodes well for future colonization. In November 2008, the Indian probe Chandrayaan 1 proved that water did indeed exist on the Moon by finding its telltale signal at the lunar south pole. The source of the water is from cometary impacts or a chemical reaction between oxygen rich lunar rocks and the hydrogen of the solar winds that blast the Moon’s surface. Liquid water would not survive on the open face of the Moon, but has been found in its solid state hidden in deep cold shadows. In fact, one of the craters, the Hermite Crater in the northern polar region is a chilly -238 degrees Celsius--colder than the surface of Pluto.
The Moon has several other surprises. Yes, it has an atmosphere, though it is so tenuous that it is nearly a vacuum, around 3 X 10-15 atmosphere (Earth’s atmosphere is one atmosphere). It also has an axial tilt, but again very slight in comparison with the Earth’s, only 1.54 degrees compared with Earth’s 23.5 degrees.
The Moon travels around the Earth once every 27.3 days (Sidereal period). Since the Earth moves in its orbit around the Sun simultaneously the phase of the Moon is going to be slightly different at about every 29.5 days (synodic period).
Such a barren world is most surely lifeless, though several early writers often wrote of life forms. One of the first such tales was written by the famous astronomer, Johannes Kepler, who discovered the laws of planetary motion. He, before 1610, wrote Somnium (published posthumously), in which a traveler finds himself transported to a Moon inhabited by aerial demons. The story was probably one of the first attempts at true science fiction as Kepler embeds several of his astronomical theories within the story. H.G. Wells, in his 1901 novel The First Men in the Moon describes a lunar world inhabited by insect-like beings called Selenites. The explorers arrive on the world via the use of a fictional material called cavorite, which effectively shields out the effects of gravity. Since that time few writers have speculated on life on the Moon, but several have hypothesized the possibility of the Moon having served as a base for alien civilizations looking down on Earth. Perhaps the most classic sequence of this concept in either literary or cinematic form of this is the discovery of an alien monolith on the surface of the Moon in Arthur C. Clarke’s and director Stanley Kubrick’s 2001: A Space Odyssey.
The Moon has probably been better probed than even some of the hidden regions of the Earth especially the depths of our oceans. Exploration with spacecraft began in earnest in the late 1950’s during the Cold War between the United States and Soviet Union.
Some early writers have come up with some bizarre ways of getting to the Moon. One, The Man in the Moone, written in 1638 by Francis Goodwin, describes a vessel pulled to the Moon by a flock of geese. Cyrano de Bergerac wrote in 1647 Voyage dans la Lune about a vessel launched by fireworks. In Vasily Levshin’s 1784 tale Newest Voyage the hero is transported to the Moon by a self-constructed winged apparatus. Wilhelm Kuchelbecker in 1824 also wrote of a trip to the Moon, entitled Land of Acephals, in a balloon. The Unparalleled Adventure of One Hans Pfaall, a story written in 1835 by Edgar Allen Poe, is about a bellows repairman who flies a giant balloon complete with an air compressor to the Moon. One of the early scientific descriptions of flight to the Moon was by Jules Verne in his 1865 novel From the Earth to the Moon. As with many of Verne’s other stories, this one has some great insights that predate any space program. He incorporated the idea of escape velocity from Earth by using a space cannon to launch a vehicle into space and had the launch site as being in Florida, long before the Kennedy Space Center was ever on anyone’s mind.
As with many early space endeavors the Soviet Union launched its lunar program before the Americans, with its Luna program. Luna 1 was the first man-made object to pass near the Moon and Luna 2 impacted with the surface and Luna 3 took photos of the far side of the Moon all in 1959. The program continued to 1976. Luna 9 was the first to have a successful soft landing and the first to fully orbit the moon was Luna 10 both in 1966. Luna 16, 20 and 24 brought back rock samples.
The United States challenged the Soviet lead and launched its own program four months after the launch of Luna 9 with the Surveyor program (1966-1968). Concurrently, President John F. Kennedy, on May 25, 1961 issued his famous challenge to the citizens of the United States, resulting in the ambitious Apollo mission which landed the first two people, Neil Armstrong and Buzz Aldrin, on the surface of the Moon in July 1969. The lunar landing program continued to Apollo 17 in 1972, all successful, with the exception of Apollo 13.
Japan became the third country, in 1990, to place a spacecraft into lunar orbit, a craft named Hiten. It released a smaller probe Hagoromo in orbit but the transmitter failed and the mission terminated.
In 1994, the United States ventured to the Moon again with Clementine, a joint United States Defense Department and NASA venture which entered lunar orbit and created a global topographic map. Lunar Prospector followed in 1998 with instruments that found evidence of water ice in permanent shadowed craters.
Other countries have also entered the lunar race. The European Space Agency’s SMART 1 was in lunar orbit in 2003 and made a first detailed study of chemical elements on the lunar surface. In 2006, it was deliberately crashed into the lunar surface. In September 2007, Japan followed its earlier mission with its second lunar orbiter mission, the Selene. It was equipped with a high definition video camera and two small radio transmitter satellites that obtained lunar geophysical data and took the first high definition movies from beyond Earth. It finally crashed onto the surface of the Moon in June 2009. China orbited the spacecraft Chang’e in November 2007 until its controlled impact in March 2008. In order to trump the success of its earlier Chandrayaan 1 mission, India has its sights not only on continuing the Chandrayaan program but also landing someone on the Moon by 2020.
Even private firms are getting in on the excitement of the Moon. Google’s Lunar X prize announced in September 2007 twenty million dollars to anyone who could land a robotic rover on the Moon. Shackleton Energy Corporation wants to establish operations on the south pole by 2020. Robert Heinlein, a one-man visionary of lunar exploration, wrote of a private citizen financed mission to the Moon in his tale Requeim. Moon Ex, an American company, is looking to launch a number of robotic missions to the Moon beginning as early as 2015.
What do we do when we get there again? One idea is colonization. Former President George W. Bush in 2004 challenged Americans to return humans to the Moon by 2019 with the prospect of a lunar base in 2024. His vision was subsequently overshadowed by competing demands of the agency responsible for space exploration, NASA.
Many science fiction tales have looked at the possibility of lunar colonization, but many of them see it as an analogy of a revolution where the colony rebels against their Earthly or corporate overlords.
Robert Heinlein’s classic The Moon is a Harsh Mistress is about a revolt of a lunar penal colony against the Earth. The novel, though written in 1966, is still relevant today in its depictions of a plausible lunar colony.
In Kim Stanley Robinson’s short story "The Lunatics" workers who mine the resources under the surface of the Moon rebel against their corporate leaders. In similar fashion in Lunar Descent, by Allan Steele, “moondogs” who mine the Moon for Skycorp rebel against the malicious corporation. In Ben Bova’s Moonrise and Moonwar a lunar base on the Moon that was built with private funds rebels against the Earth in order to allow it to declare independence and continue with its outlawed nanotechnology.
Unlike other colonial rebellion novels, Arthur C. Clarke’s Earthlight has a slightly different twist where the Moon is caught in a war between the inhabitants of Venus and Mars.
While not quite at the same intensity as the first Apollo landing on the Moon, the excitement of lunar exploration appears to have returned to the imagination of the world. Whoever will be first to land people on the Moon again or establish a colony is open to debate, but with all of the activity, in spite of NASA’s and other space agency cutbacks and competing priorities, we are truly entering an age of the days of Robert Heinlein’s’ vision where the Moon is merely an extension of the Earth. Science fiction is happening right before our eyes.
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by Peter Jekel