Abnormal? What is so abnormal about our moon – which has inspired different emotions in humankind throughout the ages – from awe, superstition to much more tender emotions such as love, etc. well, as it happens, the Moon happens to quite large as compared to its capital body around which is revolves, in fact it is the fifth largest natural satellite in the entire SOL’s (sun) Solar System. Take for example other large moons of the solar system such as Triton, Titan, IO, Europa, Cheron (what!!! – you didn’t know that Pluto had a moon too?) – They are all huge, but pale when compared to their “parent” body. In fact, Jupiter and Saturn are so big (full of gas) that their moons or satellites are very small indeed when compared to their own mass or size. The earth’s moon, in comparison, is very large indeed – in terms of diameter - a little more than a quarter that of the Earth. This means that the Moon's volume is about 2 percent that of Earth and the pull of gravity at its surface about 17 percent that of the Earth. In fact, in astronomy, it is found quite astonishing to have such a large body orbiting a relatively small core planet. Indeed, sometimes, from galactic perspective, Earth-Moon system is often referred to as the double-planet system.
By the middle of the 17th century, Galileo and other early astronomers made telescopic observations, noting an almost endless overlapping of craters. It has also been known for more than a century that the Moon is less dense than the Earth. Although a certain amount of information was ascertained about the Moon before the space age, this new era has revealed many secrets barely imaginable before that time. Current knowledge of the Moon is greater than for any other solar system object except Earth.
Various facts, especially the NASA photographs of Apollo missions are lucidly presented in this article by Rosanna L. Hamilton.
But really, how much do we know about our own galactic backyard?
The Moon makes a complete orbit around the Earth every 27.3 days (the orbital period), and the periodic variations in the geometry of the Earth–Moon–Sun system are responsible for the lunar phases that repeat every 29.5 days (the synodic period). The Moon is in synchronous rotation, meaning that it keeps nearly the same face turned towards the Earth at all times. Early in the Moon's history, its rotation slowed and became locked in this configuration as a result of frictional effects associated with tidal deformations caused by the Earth. The far side had never been seen by any human until the launch of moon probes in the last 1950’s.
You can see the Virtual Reality Moon Phase Pictures here.
The Moon is the only celestial body to which humans have travelled and upon which humans have landed. The first artificial object to escape Earth's gravity and pass near the Moon was the Soviet Union's Luna 1, the first artificial object to impact the lunar surface was Luna 2, and the first photographs of the normally occluded far side of the Moon were made by Luna 3, all in 1959. The first spacecraft to perform a successful lunar soft landing was Luna 9, and the first unmanned vehicle to orbit the Moon was Luna 10, both in 1966. The United States (U.S.) Apollo program achieved the only manned missions to date, resulting in six landings between 1969 and 1972. Human exploration of the Moon ceased with the conclusion of the Apollo program, although several countries have announced plans to send people or robotic spacecraft to the Moon – well – India and China are amongst the nations now raring to literally reach for the moon!
Okay, back to moon J
One distinguishing feature of the far side is its almost complete lack of maria. The dark and relatively featureless lunar plains which can clearly be seen with the naked eye are called maria (singular mare), Latin for seas, since they were believed by ancient astronomers to be filled with water. These are now known to be vast solidified pools of ancient basaltic lava. The majority of these lavas erupted or flowed into the depressions associated with impact basins that formed by the collisions of meteors and comets with the lunar surface. Maria are found almost exclusively on the near side of the Moon, with the far side having only a few scattered patches covering only about 2% of its surface compared with about 31% on the near side.
The lighter-colored regions of the Moon are called terrae, or more commonly just highlands, since they are higher than most maria. Several prominent mountain ranges on the near side are found along the periphery of the giant impact basins, many of which have been filled by mare basalt. These are believed to be the surviving remnants of the impact basin's outer rims. In contrast to the Earth, no major lunar mountains are believed to have formed as a result of tectonic events.
The Moon's surface shows obvious evidence of having been affected by impact cratering. Impact craters form when asteroids and comets collide with the lunar surface, and globally about half a million craters with diameters greater than 1 km can be found. Since impact craters accumulate at a nearly constant rate, the number of craters per unit area superposed on a geologic unit can be used to estimate the age of the surface (see crater counting). The lack of an atmosphere, weather and recent geological processes ensures that many of these craters have remained relatively well preserved in comparison to those found on Earth. The largest crater on the Moon, which also has the distinction of being one of the largest known craters in the Solar System, is the South Pole-Aitken basin. This impact basin is located on the far side, between the South Pole and equator, and is some 2,240 km in diameter and 13 km in depth.
Blanketed atop the Moon's crust is a highly comminuted (broken into ever smaller particles) and "impact gardened" surface layer called regolith. Since the regolith forms by impact processes, the regolith of older surfaces is generally thicker than for younger surfaces. In particular, it has been estimated that the regolith varies in thickness from about 3–5 m in the maria, and by about 10–20 m in the highlands. In other words, the soil is thick and slick…
But why the rush of back to moon, why now?
India launched Chandrayaan-1 - in a historic feat, on October 22, 2008 from the Satish Dhawan Space Centre in Sriharikota. The successful launch of India's maiden unmanned moon mission Chandrayaan-1 has catapulted the country into the league of a select group of nations. One of the prime reasons is national pride and then the other is the possibilities it affords. With the western economy in decline and ascendency of India and China in this century, it was only a matter of time before these two nations realized the importance of breaking the bounds of earth’s puny gravity well and soar beyond.
But beyond the political hype and all the aspirations of becoming a superpower, there is a much more practical aspect to race towards the moon.
The Moon holds several minerals and elements not found or manufactured easily on earth. Helium-3 for example. Then there are spin-off benefits from the technology that must be developed to reach moon. The sophistication and cost effectiveness of the journey outwards ultimately holds the key to cheap and profitable exploration of outer space.
India's love fest with deep space has only just begun. It could well become a force to reckon with giving the established space agencies a run for their money as the Indian moon mission is the cheapest till date of all moon missions in this century, but one also which creates a world record of carrying the largest suite of scientific instruments ever to be carried to the moon till date.
And frankly, I would want to see a difference from NASA – whose every mission has to cost a billion dollars and then explode either while leaving or entering earth’s gravity well. I’ve got nothing against NASA – bunch of great guys (lot of Indians there in fact if I heard it right), but everything they do - why DOES IT HAVE TO COST SO MUCH?
If the technology wasn’t ready to allow human exploration of space in a safe way, why send humans? Robotic vehicles can also operate with certain amount of efficiency and the money could have been better utilized in developing technologies which would have ultimately resulted in cheaper access to outer space.
And now NASA’s mantra has indeed become – faster, cheaper and better (FCB) – evident in the Mars probes.
In fact, if the price tag wasn’t so high, space exploration would have proceeded at a much quicker pace than what happened in the aftermath of Apollo missions.
We keep on saying that man has landed on the moon and we are not exploring our own cosmic backyard. But, without the intention of belittling our (humankind’s) achievements so far, what we have done till now is slingshot a few missions to moon (with humans in it), put a space station in orbit (with the ever present danger of it falling down on our heads – e.g. MIR) and sent some probes to near by planets. Voyager I & II and the pioneer missions were an exception. They were real value for their money because of the wealth of information that they afforded to humanity about the outer side of our solar system.
I would closely watch India and humanity’s collective progress of back to the moon, mars and then ultimately the solar system.
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