Sunday, August 26, 2012

Alas, Poor Theia!

Earth's Moon is the brightest and largest object in the star-splattered night sky. It is an enchanting and lovely companion world, the fifth largest moon in our Solar System. Earth's Moon is mysterious and beckoning, an age-old symbol for love, fleeting beauty, and that which is feminine. But where did our Moon come from?

Earth's Moon is our nearest neighbor. More than 100 moons orbit the eight major planets in our Solar System. The majority of them are frigid worlds, made up primarily of ice and some rocky material, circling the giant planets inhabiting the outer limits of our Solar System--Jupiter, Saturn, Uranus, and Neptune. The inner Solar System is almost devoid of moons. Our own Moon is the largest one in our region of the Sun's family. Of the four relatively small, rocky inner planets that circle nearest to the Sun--Mercury, Venus, our Earth, and Mars--Mercury and Venus are moonless, and Mars is circled by two misshapen, miserable excuses for moons, Phobos and Deimos. The two Martian moons are quite small and are likely kidnapped asteroids from the Main Asteroid Belt that whirls around our Sun between the orbits of Mars and Jupiter.

A moon is usually defined as a natural object that is in orbit around a planet. The moon is kept in its orbit by the host planet's gravity, as well as the gravity of the moon itself. Some planets host moons; some do not.

At least five theories have been suggested explaining how our Moon was born. The first theory states that the Moon was once a part of our own planet, and then somehow budded off about 4.5 billion years ago, when our Solar System was first forming. The Pacific Ocean basin is the most frequently suggested site for where our Moon originated. A second theory suggests that the Earth and Moon formed together out of the original nebula that gave birth to our Solar System. The third theory states that the interaction of Earth-orbiting and Sun-orbiting planetesimals, early in the history of our Solar System, resulted in their disintegration. Earth's Moon then condensed from this debris. Planetesimals were the building blocks of the planets in the early Solar System, and they were rocky, icy, or both. They collided and then stuck together to form the planets. The fourth theory states that our Moon was actually born elsewhere in the Solar System, and was eventually kidnapped by our planet when it ventured too close to Earth's gravitational embrace.

However, the theory that is currently considered to be the most credible is usually called the giant impact theory, or alternatively (and playfully), the Big Whack or Big Splash theory. The fundamental suggestion of this theory is that a hypothetical Mars-sized protoplanet, named Theia by astronomers, crashed into the primordial Earth billions of years ago. The catastrophe resulted in a portion of the ancient Earth's crust to be shot off into space, hoisting a myriad of moonlets into the sky. Some of this debris was eventually captured into orbit around the ancient Earth about 4.5 billion years ago, where it was eventually pulled together by the force of gravity to become our lovely Moon!

Most of the giant impact theory was first presented back in 1975 by Dr. William K. Hartmann and Dr. Donald R. Davis of the Planetary Science Institute in Tucson, Arizona. Their theory is based on geological samples gathered by Apollo astronauts when they made their historic voyage to the Moon in July 1969. The oxygen isotopes found within the gathered Moon rocks proved to be almost identical to those of our own planet! An isotope refers to each of two or more types of the same element containing equal numbers of protons but different numbers of neutrons in their atomic nuclei. In addition, other pieces of evidence suggested strongly that the Moon is composed primarily of the same material that is found in the Earth's mantle.

Evidence presented in the October 18, 2012 issue of the journal Nature adds still more credibility to the Big Whack scenario. Planetary scientists, examining Moon-rocks gathered during NASA's Apollo Moon-landing missions, as well as a meteorite that is known to be a chunk of the Moon, searched for traces of zinc in the lunar samples. The ratios of heavy to light isotopes were revealed to be greater than on our planet. This indicates that the Moon experienced a violent evaporation event when our Solar System was first forming. This catastrophic event may well have been the ancient, violent collision of a Mars-sized world--Theia--with the primordial Earth. The study clearly provides additional evidence that Earth's Moon was formed in the wake of a gigantic impact, the scientists explained.

When our Moon was still forming, it is thought to have sported a fiery, global magma ocean that was hot enough to vaporize zinc. A catastrophic impact is one of the few events that would be capable of generating that immense quantity of heat. A second prediction of the Big Whack is that heavier isotopes would exist in greater abundance. This is because they would condense at hotter temperatures.

Dr. Frederic Moynier, assistant professor of Earth and Planetary Sciences at Washington University in St. Louis, Missouri, told the press on October 17, 2012 that "What we found is that the depletion [of lighter isotopes] of zinc is probably due to evaporation." Dr. Moynier is one of the study's co-authors.

Dr. Moynier, the paper's lead author Dr. Randal Paniello and Dr. James Day of the Scripps Institute of Oceanography in California, discovered that the ratio of zinc-66 to zinc-64 contained in the lunar rocks is approximately three to four times greater than that found on either Earth or the planet Mars. On Mars it is 0.27 parts per thousand, while on Earth it is 0.25 parts per thousand. In contrast, on the Moon, it was a difference of 1.3 to 1.4 parts per thousand--a very significant difference!

Almost all of the lunar samples gathered from the Moon showed similar ratios of heavier to light isotopes, even though they were collected from different regions scattered all over the Moon.

The extremely high temperatures suggest that water vaporized. This further indicates a depletion of other volatiles, which are elements such as sulfur, chlorine, and hydrogen, which all vaporize at much lower temperatures. However, it must be noted that there are several studies suggesting that water is still present in some Moon-rocks.

Exactly how much water and other volatiles Earth's Moon contains is still a key question. Planetary scientists who suggest that there is water in the lunar mantle say that the Moon may have large quantities of those chemicals. However, other planetary scientists argue that the volatiles are primarily located in the upper layers of the Moon's soil, carried in by meteorite impacts and mostly dating from the ancient era of lunar formation.

Water and volatiles most likely resulted from impacts and solar wind, Moynier told the press in October 2012. "[The results] show that all this water they found on the face of the Moon is secondary water," he added.

Still another model, devised by Dr. Matija Cuk and Dr. Sarah Stewart of Harvard University in Cambridge, Massachusetts, explains the amazingly similar chemistry of our own planet with its lovely Moon. A giant impact onto a fast-spinning Earth shoots material from Earth into orbit, giving birth to a Moon that is just like our own--depleted in iron, with a composition similar to Earth's mantle. After the impact, the once-rapidly spinning Earth is slowed down by a gravitational dance between the Moon and the Sun, termed an orbital resonance.

Of late, the Big Whack theory has lost some credibility because the Earth and its Moon have been shown to be "isotopic twins". The original Big Whack theory predicted that most of Earth's Moon was composed of Theia-stuff rather than Earth-stuff, and therefore should have shown a different isotopic composition.

Therefore, the giant impact theory was in trouble because, even though it could match the mass of the Moon and the rotation rates of the Earth and its Moon, it could not correctly predict the lunar chemical composition. Currently, tides between the Earth and Moon have slowed down Earth's orbit, and have also pushed the Moon further and further away. In the early days of our Solar System, the Moon was much closer to our planet than it is today--a gigantic companion world taking up a large part of the sky. The ancient Earth possessed a mere five-hour day when the Moon was born. If the Earth had a spin of a mere five hours after the impact, the crash of Theia could not have shot enough Earth-stuff into orbit to create a Moon with a chemistry that matched that of Earth.

However, Cuk and Stewart were able to demonstrate that if Earth's initial angular momentum were higher, corresponding to an Earth day of between two and three hours, a catastrophic impact could indeed shoot enough Earth-stuff into orbit to create a Moon that has the same isotopic composition as Earth. With this extremely fast rotation rate, it is much easier to shoot Earth-stuff into orbit as the result of a giant impact.

Cuk and Stewart also calculated that the ancient Earth could well have possessed such a short rotation period after the crash and then later have attained its current much more sluggish spin-rate by transferring angular momentum to the Sun by way of evection resonance. Evection resonance refers to the gravitational dance between Earth's orbit circling the Sun and the lunar orbit around Earth. This paper has revealed for the first time that it is indeed possible for the ancient Earth to have possessed a spin rate of only two or three hours after the giant impact.

But where did Theia go after it had smashed into the ancient Earth, causing the formation of our enchanting large Moon? That is the question! No trace of this hypothetical ancient world has ever been observed--and it has not been for lack of trying. If Theia or its remnants and relics are ever observed by astronomers it will at long last explain the mysterious origin of Earth's luminous, captivating companion.

I am a writer and astronomer whose articles have been published since 1981 in various magazines, newspapers, and journals. Although I have written on a variety of topics, I particularly love writing about astronomy because it gives me the opportunity to communicate to others the many wonders of my field. My first book, "Wisps, Ashes, and Smoke," will be published soon.

Sunday, August 19, 2012

Wild Horse Asteroids

asteroids are a large group of objects that swarm around in the same orbit as the gas-giant planet Jupiter--the largest planet in our Solar System. The total number of Trojan asteroids larger than 1 kilometer is thought to be about 1 million. Like wild horses, the asteroids gallop through space in herds, with one tumbling, zipping swarm leading the way in front of Jupiter, and a second swarm whizzing in from behind. But where did the Trojans come from?

There are now thousands of Trojans known--amounting to about the same number thought to inhabit the Main Asteroid Belt between Mars and Jupiter. The first Trojan was spotted on February 22, 1906, by German astronomer Max Wolf, who found the galloping object in the herd leading ahead of Jupiter. It was named Achilles by Wolf, and it is approximately 135 kilometers in diameter. Each of the Trojans is named for a hero of the Trojan War, in honor of the legend in which Greek soldiers hid inside a giant wooden horse statue in order to launch a surprise invasion of Troy, and attack that ancient city's people. The largest of the Trojans is 624 Hektor, which has a diameter of about 203 kilometers. It is thought that the smallest of the swarming Trojans are merely the leftovers from collisions between crashing larger Trojans.

Asteroids and comets are lingering relics of our Solar System's ancient past. Our Solar System was born about 4.6 billion years ago due to the gravitational collapse of a small dense knot within a giant, cold, dark molecular cloud. Most of the collapsing mass congealed at the center, giving birth to our Star, the Sun. The rest flattened into what is termed a protoplanetary disk from which the planets, moons, asteroids, comets, and other small Solar System bodies emerged. This generally accepted model, termed the nebular hypothesis, was first suggested back in the 18th century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace.

Protoplanetary disks have been spotted circling a number of stars inhabiting young star clusters. They form when a baby star is born, but at the earliest stages cannot be seen because they are swathed by an impenetrable, opaque, veiling envelope. The accretion disk, which nourishes the central baby protostar is thought to be both very massive and searing-hot. The temperature can easily skyrocket above 1,000 Kelvin within 1 Astronomical Unit (AU) from the baby star, and 400 Kelvin inside 5 AU.One AU is the average distance between Earth and the Sun, which is 93,000,000 miles.

Accretion disks can hang around for about 10 million years. By the time the young star reaches what is termed the T Tauri stage, the disk has grown both cooler and thinner. A T Tauri star is an extremely youthful and energetic variable star that is less than 10 million years old, and possesses a mass that is similar to, or perhaps a bit less, than that of our Sun. T Tauri stars have diameters that are several times greater than that of our Star, and they are still in the process of shrinking. By the time a bouncing baby star has reached this stage, less volatile materials have already started to condense near the center of the accretion disk, forming very tiny, smoke-like dust grains that contain crystalline silicates.

These dust particles are bestowed with a natural stickiness and therefore tend to glue themselves together in the dense disk environment, leading to the formation of ever larger particles up to several centimeters in size. Further aggregation results in the formation of planetesimals, which are the building blocks of planets. The planetesimals can be 1 kilometer across or even larger. Planetesimals are extremely abundant, and they tend to spread throughout the protoplanetary disk--and some remain as relics long after the formation of a planetary system. Asteroids, such as those found in our own Solar System, are believed to be left-over rocky planetesimals. Comets, on the other hand, are thought to be the relic icy planetesimals from the outer limits of a Solar System such as our own. The asteroids are the leftover building blocks of the rocky inner planets--Mercury, Venus, Earth, and Mars--while the comets are the leftover building blocks of the outer giant planets, which are Jupiter, Saturn, Uranus and Neptune.

Astronomers using data obtained from NASA's Wide-field Infrared Survey Explorer (WISE), have succeeded in obtaining some new and important clues in respect to the mysterious origins of Jupiter's herds of Trojans. These observations are the first to obtain a detailed analysis of the Trojans' colors. The new observations reveal that the leading and trailing Jovian attendant herds are composed of mainly dark, reddish rocks with non-reflecting, somewhat dull surfaces. Also, the leading herd is more numerous than the trailing one.

WISE has succeeded in revealing that the two separate herds of galloping Trojans are similar, and it therefore sheds some light on the baffling origin of these asteroids. Apparently, both herds do not contain invaders from other regions of our Solar System! Furthermore, the Trojans do not resemble asteroids dwelling in the Main Asteroid Belt--neither do they bear a family resemblance to the comet-like objects spinning around in the icier, darker, and more remote region near the dwarf planet Pluto, known as the Kuiper Belt.

"Jupiter and Saturn are in calm, stable orbits today, but in their past, they rumbled around and disrupted any asteroids that were in orbit with these planets. Later, Jupiter re-captured the Trojan asteroids, but we don't know where they came from. Our results suggest that they may have been captured locally. If so, that's exciting because it means these asteroids could be made of primordial material from this particular part of the Solar System, something we don't know much about," explained Dr. Tommy Grave in an October 15 2012 NASA Jet Propulsion Laboratory (JPL) Press Release. Dr. Grav is a WISE scientist from the Planetary Science Institute in Tucson, Arizona. He is also a member of the NEOWISE team, which is the asteroid-hunting component of the WISE mission. JPL manages, and operates, WISE for NASA's Science Mission Directorate. The spacecraft soared into orbit on December 14, 2009, and was put into hibernation mode in 2011, after it had succeeded in scanning the entire sky twice, completing its primary mission.

Before WISE, the primary mystery in regard to this population of objects was determining how many of them pranced around in the two herds of space rock and ice, both leading and following Jupiter.

Grav continued to note that "The two asteroid camps even have their own 'spy'. After having discovered a handful of Trojans, astronomers decided to name the asteroid in the leading camp after the Greek heroes and the ones in the trailing after the heroes of Troy. But each of the camps already had an 'enemy' in their midst, with asteroid 'Hector' in the Greek camp and 'Patroclus' in the Trojan camp."

The NEOWISE team has successfully determined the colors of hundreds of Jupiter's Trojans. This has enabled many of these objects to be sorted according to asteroid classification schemes for the very first time.

"We didn't see any ultra-red asteroids, typical of the Main Belt and Kuiper Belt populations. Instead, we find a largely uniform population of what we call D-type asteroids, which are dark burgundy in color, with the rest being C- and P- types, which are more grey-bluish in color. More research is needed, but it's possible we are looking at some of the oldest material known in the Solar System," Grav continued to explain in the October 15, 2012 JPL Press Release.

Other planets have also been found to have their own retinues of Trojans--they are Mars, Neptune, and our own Earth! WISE was responsible for discovering the very first Earth Trojan!

I am a writer and astronomer whose articles have been published since 1981 in various newspapers, journals, and magazines. Although I have written on a variety of topics, I particularly love writing about astronomy because it gives me the chance to communicate to others the many wonders of my field. My first book, "Wisps, Ashes, and Smoke," will be published soon.

Sunday, August 12, 2012

Diamond Planet

"Curiouser and curiouser," exclaimed Alice, lost in a Wonderland inhabited by a truly impressive array of oddballs. Her words can easily be echoed by today's planet-hunters who search for extrasolar planets--planets that circle stars other than our Sun--who have managed to discover a bizarre array of other"oddballs" dwelling in our Milky Way Galaxy.

Scientists have been searching for planets orbiting stars beyond than our Sun for a very long time. In the 18th century, the possibility of the existence of extrasolar planets was mentioned by Sir Isaac Newton in the General Scholium that ends his Principia. Newton, making a comparison to the Sun's own familiar family of planets, writes: "And if the fixed stars are the centers of similar systems, they will all be constructed according to a similar design and subject to the dominion of One."

Many times during the 20th century, ecstatic astronomers announced what they thought was the first sighting of a planet beyond our own Solar System. They then looked on unhappily as other astronomers failed to confirm their "discoveries". In 1992, however, one happy radio astronomer hit the elusive jackpot and announced evidence confirming the existence of two extrasolar planets circling around a dense little stellar corpse in the Milky Way.

Astronomer Dr. Alexander Wolszczan of Pennsylvania State University made his announcement after observing radio emissions from a compact millisecond pulsar located about 1,300 light-years from Earth. One light-year is the distance that light can travel in a vacuum in one year--5,880,000,000,000 miles!

The pulsar, known by the bland name of PSR B1257 + 12, is a tiny dense denizen of the Virgo constellation. A pulsar is a little ball, perhaps about 12 to 20 miles in diameter, in which the collapsed core of a massive star, containing up to 1,000,000,000 tons of matter, literally is squeezed to the size of a city on Earth. A pulsar is a spinning neutron star--the relic core of a massive star that has died in a spectacular supernova blast--and these exotic objects have a density that is equivalent to 1,000,000 times that of the density of water.

It was later determined that PSR B1257 + 12 is orbited by several planets--and they are true "oddballs". They are probably rocky bodies, like the Earth, but that is where all resemblance ends. Pulsar planets, unlike Earth, can have no atmosphere. They are extremely unpleasant worlds, showered mercilessly by deadly radiation.

The vicinity of a pulsar was about the last place astronomers expected to observe planets. Such oddities should have tipped astronomers off to the existence of many, many more "oddballs" to come.

And, come they certainly did! Although the pulsar planets were the first extrasolar planets to be discovered, astronomers still sought the "Holy Grail" of planets circling a normal "main-sequence" (hydrogen-burning) star like our Sun. Triumph came in 1995, when astronomers Dr. Michel Mayor and Dr. Didier Queloz of Switzerland's Geneva Observatory announced the first convincing evidence of an extrasolar planet circling a normal Sun-like star dwelling outside of our own Solar System. However, the newly discovered extrasolar planet turned out to be a true "oddball" because it was as hefty as Jupiter--the largest planet in our Solar System--but it circled its star at a mere fraction of the distance between Mercury and the Sun. The star that hosts the roasting planet is dubbed 51 Pegasi, and the strange planet was suitably named 51 Pegasi b. 51 Pegasi b was the first extrasolar planet spotted belonging to a new class of objects termed "hot Jupiters"--giant gaseous planets orbiting fast and close around their parent stars. So far, most of the extrasolar planets discovered have been "hot Jupiters". This is because most of the extrasolar planets were discovered using the Doppler (radial velocity) method, which favors the discovery of giant planets that orbit fast and close to their fiery parent stars. However, there are other methods, in addition to the radial velocity method, that are now being used. Those other methods are able to spot smaller worlds that twirl around their stars in more distant orbits. For example, planet-hunters are now discovering transiting extrasolar planets, which are planets that float directly in front of the face of their star. Also, gravitational lensing techniques are currently being used to discover extrasolar worlds. Gravitational lensing is a prediction of Albert Einstein's General Relativity whereby a large, foreground celestial object bends, or distorts, the light emitted by a more distant object.

Since those initial discoveries in the mid 1990s, astronomers have discovered planetary systems akin to our own Solar System, as well as increasingly smaller and smaller planets--planets the size of our own Solar System's Uranus and Neptune. Planet-hunters have now succeeded in spotting much smaller planets approaching our own Earth in size. With decreasing size, astronomers expected to discover increasingly Earth-like worlds. While this may indeed be the case in many instances, smaller worlds have proven that they can be just as odd as many of the much larger extrasolar planets observed so far.

Super-Earths are bizarre extrasolar planets that are unlike any that dwell in our own Solar System. They are smaller than the familiar four giant planets that circle our Sun--even Neptune, which is our Solar System's smallest giant planet. But Super-Earths are more massive than our own Earth, and they can be composed of rock or gas or both! The extrasolar planet 55 Cancri e was discovered orbiting a nearby star in our Milky Way Galaxy, and it is a very dark, carbon-rich, rocky world. In October 2012, amazed astronomers announced that at least one-third of this "oddball's" mass is composed of diamond!

55 Cancri e has a radius about twice that of our planet, and its mass is eight times greater. It orbits the nearby Sun-like star, 55 Cancri, which is located about 40 light-years from Earth in the constellation Cancer. This "oddball" world is one of a family of five planets circling that star, whipping around it at breathtaking speed. 55 Cancri e circles its star in a mere 18 hours--in marked contrast to Earth's year which is 365 days long! The planet is searing-hot, with a sizzling temperature of 3,900 degrees Fahrenheit. Such a hostile world is not likely to harbor delicate living creatures.

This bizarre planet was first observed transiting its parent star in 2011. This enabled astronomers to measure its radius. This newly acquired information, combined with an estimation of the planet's mass, allowed Dr. Nikku Madhusudhan, a Yale University postdoctoral researcher, and his colleagues, to determine its chemical composition. The researchers accomplished this feat by using models of the planet's interior and by computing all possible combinations of elements and compounds that could yield those characteristics.

"This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth. The surface of this planet is likely covered in graphite and diamond rather than water and granite," Madhusudhan noted in the October 11, 2012 Yale News.

Astronomers had earlier reported that 55 Cancri contained more carbon than oxygen. Dr. Madhusudhan and his coworkers went on to confirm that large quantities of carbon and silicon carbide, as well as a tiny quantity of water ice, were available when 55 Cancri e was in the process of forming.

Astronomers had also suggested previously that 55 Cancri e contained a very large quantity of super-heated water--basing this on the assumption that the "oddball" world possessed a chemical composition similar to that of Earth.

However, the new research indicates that the planet really has no water at all! In fact, 55 Cancri e is apparently composed mostly of carbon--in the form of diamond and graphite, iron, silicon carbide, and, perhaps, silicates. The study further indicates that at least a third of the "oddball's" mass--which is equivalent to that of three Earths--could be diamond!

The identification of a carbon-rich Super-Earth indicates that remote rocky planets circling stars beyond our Sun can no longer be assumed to have interiors, atmospheres, chemical constituents, or biologies akin to those of our own planet, Madhhusudhan continued to explain. This discovery also opens new vistas for the study of geophysical processes and geochemistry in Earth-sized distant worlds. A carbon-rich composition could play a starring-role in a planet's plate tectonics and thermal evolution--with strong implications for mountain formation, volcanism, and seismic activity.

Dr. David Spergel, professor of astronomy and chair of astrophysical sciences at Princeton University, who was not a co-author of the study, noted in the October 11, 2012 Yale News that "Stars are simple--given a star's mass and age, you know its basic structure and history. Planets are much more complex. This 'diamond-rich-super-Earth' is likely just one example of the rich sets of discoveries that await us as we begin to explore planets around nearby stars."

This new research represents the first time that astronomers have spotted a likely diamond planet around a Sun-like star and specified its chemical composition.

The paper is titled "A Possible Carbon-rich Interior in Super-Earth 55 Cancri e", and has been accepted for publication in the journal Astrophysical Journal Letters. The authors of the paper are Madhusudhan, Yale University geophysicist Dr. Kanani Lee, and Dr. Olivier Mousis, who is a planetary scientist at the Institut de Recherche en Astrophysique in Toulouse, France.

I am a writer and astronomer whose articles have been published since 1981 in various newspapers, magazines, and journals. Although I have written on a variety of topics, I particularly love writing about astronomy because it gives me the opportunity to communicate to others the many wonders of my field. My first book, "Wisps, Ashes, and Smoke," will be published soon.

Sunday, August 5, 2012

Sex and Space: Contrary Imperatives

So I just read another article by a space enthusiast. And yet again, it ended with a declarative statement about how the American public must understand the importance of space exploration. And yet again, it ended with an impassioned exclamation point. It is as if that explanation point was going to make people realize in a single split second that they had missed the boat all their lives. Now they understand. Now it is clear. Space is the most important thing in their life. How could anyone have missed that?

For all the space enthusiasts of the world, and I count myself among them; here is something you need to know. Space exploration is not the most important thing in the world. And if we are talking about America, there are a whole lot of other things our fellow countrymen and women spend their time and money on. And you guessed it; sex is right up there at the top of the list.

Extraordinary when you think about it. The simple biological act of sex occupies more of our thoughts, time, and money than politics, religion, education, or (of course) space. Is it fun? Yes, of course. But so is flying to outer space. In fact, a majority of males interviewed by Futron Corp. would travel to space on a sub orbital launch if given the opportunity to do so. Perhaps it is because sex is important for the continuation of our species? But then I could offer the same rational about space colonization, environmentalism, or clean energy. And you don't see advertisements for those things in every subway car, magazine, all over the internet, men's bathrooms, etc.

Sex vs. Space

So what is the logic of asserting there is a choice space vs. sex? I mean, obviously there are two very different things. But we would get a relative understanding of the value of each, just as it could be done between space and sports, movies, NASCAR, etc. Any endeavor in which a democratic society spends its dollars, privately or through taxes, is a valid means of determining the relative values of that society. So a simple look at American's expenditures should be a representation of the values of our nation. Now, this is where it can get depressing.

So for all my fellow space geeks let's take a minute and look at what America finds really important. What do they spend their money on? Don't shoot the messenger but much of the answer seems to be in attracting a potential mate, keeping one, or ensuring one's own standing in society. Certainly this appears to be the case given how much American's spends to look good. Each year, Americans spend over $250 billion on fashion (including accessories). Separate to that, Americans spend about $7 billion annually on cosmetics. (Just, FYI another $7 billion is spent annually globally on organic and natural cosmetics.) And how could anyone be attractive without the $10 billion spent annually in the United States on cosmetic surgery? Approximately $1.5 billion is spent on breast augmentation, $1.3 on Lipoplasty, $684 million Abdominoplasty (tummy tucks), etc. And just to top it off, the American online dating industry has 40 million users and has $1.9 billion in annual revenue. If you were the only person on the planet would you spend even a nickel on this stuff? Of course you wouldn't. But I think you get the point. We Americans spend a hell of a lot of money to date, mate, and look just good. I haven't researched the figures but I'll go out on a limb here and say the amount of money we spend on entertainment probably competes with trying to achieve beauty at nearly any cost.

So who are we anyway?

My fellow space enthusiasts should consider the question "Who are we?" Well, a distinct answer can be found in every society, because every society raises people to serve its needs. This process has proven true throughout human history (cavemen, ancient Egypt, Nazi Germany, etc.) Every society raises its population to serve its own needs. And it is the owners of that culture who decide what is needed in society. Range of thought is limited by the dominant values of that society.

In the United States we are lucky that the national culture is quite fractured. There are different and competing value systems. There is a dominant Judeo-Christian religious backbone but even that value system is not only changing, but also has a wide range of liberal to conservative intepretations. If the expenditures on fashion are any kind of statement (get it? fashion statement) then the liberal side appears to be winning. Other owners of our cultural value system include government, business, media, and education. Simply put, all these institutions create an environment. And the environment creates people. Change the environment and behavior changes. Remember, all these institutions created and maintained by society compete for our attention, time, and money. We elevate one at the expense of another.

How we CAN change the future

People can change the dominant value in a society. But ranting and raving in Op-Ed pieces won't do it. To move a society towards increasing its investment in space exploration requires a well-planned and coordinated strategic plan that systematizes the process of galvanizing to action policymakers, stakeholders organizations, and citizens towards a common objective. This strategic education and outreach effort includes the citizenry, government officials, non-government organizations such as academia, trade associations, media, businesses, and the aerospace industry.

Wednesday, August 1, 2012

Triton: Neptune's Kidnapped Moon

Galileo Galilei first spotted the planet Neptune with his primitive "spyglass" on December 28, 1612. He observed it again on January 27, 1613. Unfortunately, on both occasions, Galileo thought that the giant, remote planet was a fixed star, appearing near the planet Jupiter in the dark night sky. Because of this mistake, Galileo is not credited with the discovery of Neptune.

The beautiful, banded, blue ice-giant planet, Neptune, is the furthest major planet from the Sun. It is also orbited by a very weird large moon that may not have been born a moon at all. The moon, Triton, is about 1,680 miles in diameter, and sports features that eerily resemble those found on the dwarf planet Pluto. Pluto is a denizen of the Kuiper Belt. The Kuiper Belt is a reservoir of comets and other icy bodies--some large, some small--that circle around our Sun beyond the orbit of Neptune, at a distance of about 30 to 55 Astronomical Units (AU) from our Star. One AU is equal to the average distance of Earth from the Sun--approximately 93,000,000 miles.

Triton and Pluto share roughly the same bulk composition and density, as well as similar atmospheres. In addition, both remote bodies move in unusual orbits. Pluto has a highly eccentric orbit, and is sometimes closer to the Sun than Neptune! Furthermore, Pluto orbits in the opposite direction around our Sun than do the eight major planets of our Solar System. Triton revolves around Neptune in a direction counter to that of its planet--and its retrograde orbit indicates that it is a captured object. Because of the unusual nature of both Triton's and Pluto's orbits, as well as the similarities of their bulk properties and atmospheres, it has long been thought that there is some sort of historical connection between them. Indeed, it was once thought that Pluto was an escaped moon of Neptune, but this is now considered unlikely. It is much more likely that long ago Triton, like Pluto, circled the Sun independently, but was unluckily captured by its adoptive planet--whereas Pluto was left to wander freely.

Neptune, the eighth major planet from the Sun, and its neighboring sister-planet, Uranus--the seventh planet from the Sun--are both classified as ice-giants because their large cores are icy, and they never managed to acquire the immense gaseous envelopes of the two true gas-giants, Jupiter and Saturn. The gas giants are possibly composed entirely of gas and liquid, although they may have small solid cores. In contrast, the ice-giants have large solid cores and thinner atmospheres. The two gas-giants, being mostly atmosphere, are very lightweight for their size. Saturn is the lightest planet in our Solar System, despite its immense diameter. In fact, Saturn is light enough to float like a huge raft in water, provided there was an ocean big enough for it to bob around in.

The spacecraft Voyager 2 flew past Uranus in 1986, and Neptune in 1989. Voyager 2 sent back images of Neptune to Earth that revealed a strikingly beautiful deep blue planet, that sported stripes and bands, and spot-like storms akin to hurricanes. Neptune's bands and spots are different shades of blue--and these lovely shades of blue are caused by atmospheric methane, not oxygen. Some of Neptune's frothy storms are white, and look like whirling marshmallows.

Triton is the largest of Neptune's 13 moons. It is an unusual world, twirling around its planet in the wrong direction. Many astronomers think that some time in the remote past, Triton was nudged out of its home in the Kuiper Belt, and during its wanderings in the darkness of interplanetary space, at last swept close enough to Neptune to feel the irresistible lure of that planet's gravity. As Neptune drew Triton into its gravitational embrace, that luckless wanderer from the Kuiper Belt underwent a sea-change from a comet-like denizen of our Solar System's outer limits, to a moon of one of the major planets. So, there Triton whirls around in its new home, circling its planet Neptune, but circling it backwards. And like all moons, it is now a dependent of its parent planet. As a matter of fact, the moon was given the name of Triton as an allusion to the demigod Triton's dependence on the sea-god Neptune in Greek mythology.

Like Earth's own large Moon, Triton is locked in synchronous rotation with its planet--one side always faces Neptune. However, because of Neptune's odd orbital inclination, both of the moon's polar regions take turns facing the Sun. Spacecraft images of Triton reveal mounds and round pits formed from icy lava flows (cryovolanism), as well as smooth volcanic plains. The surface of the moon is only sparsely cratered, indicating that its surface is new--that is, it is constantly being resurfaced, probably by the "lava" flow from icy volcanoes. Triton is very bright--its fresh, sparkling, new ice-coating is believed to cover a heart of metal and rock. Triton's high density suggests that it contains more rock in its interior than the icy moons of Saturn and Uranus.

Triton also possesses a thin atmosphere composed mainly of nitrogen, and a smaller quantity of methane. This atmosphere probably is the result of Triton's cryovolcanism, which is enhanced by seasonal heating from the Sun. Although little is currently known of Pluto's atmosphere, it is thought to be primarily composed of nitrogen with some carbon monoxide and methane added to the mix--and it is extremely tenuous. Pluto's very thin atmosphere may exist as a gas only when Pluto is nearest to the Sun (perihelion). For most of Pluto's very long year, the atmospheric gases are frozen in the form of ice on its extremely frigid surface. One year on Triton is almost 248 Earth-years long--or 90,471 Earth-days!

Triton is one of the coldest bodies in our Solar System. In fact, it is so cold that most of its nitrogen atmosphere is condensed as frost, giving its surface a very bright, mirror-like surface, that reflects about 70% of the sunlight that reaches it.

Astronomers suspected for a very long time that Triton was not born a moon of Neptune, but was instead a luckless refugee from elsewhere that had been kidnapped by its planet. It was not until 2006, however, that a convincing theory explaining how Triton was ensnared by its adoptive parent was proposed. This theory suggests that Triton once had a companion as it orbited the Sun. According to this scenario, Neptune's strong gravitational embrace tugged Triton away from its sister world. This research was reported in the May 11, 2006 issue of the journal Nature.

"We've found a likely solution to the long-standing problem of how Triton arrived in its peculiar orbit. In addition, this mechanism introduces a new pathway for the capture of satellites by planets that may be relevant to other objects in the Solar System," explained Dr. Craig Agnor, a researcher from the University of California, Santa Cruz, in the May 10, 2006 issue of Time Magazine.

The model indicates that Triton originated as part of a binary system, much like Pluto and its large moon Charon. "It's not so much that Charon orbits Pluto, but rather both move around their mutual center of mass, which lies between two objects," Agnor added.

Gravity can pull binary systems apart when the sister objects travel too close to a massive body--such as the planet Neptune. The orbital motions of the two sister objects results in one member traveling slower than the other. This can disrupt the system and permanently alter the orbital companion. This mechanism is termed an exchange reaction, and it could have shot Triton into a number of different orbits around Neptune, Agnor continued.

In 2006, NASA dispatched the New Horizons spacecraft to visit the outer limits of our Solar System--the Kuiper Belt where the dwarf planet Pluto dwells, along with trillions of icy comets, and a multitude of other larger icy bodies--and where it is thought that the adopted moon Triton was born. The spacecraft will reach this mysterious and unexplored region in July 2015, when it flies by the icy dwarf planet and its moons--including the large moon Charon. New Horizons will shed light on the weird worlds and bizarre objects dwelling in the outskirts of our Solar System.

As for Triton--it's a doomed world. It circles around its parent planet in the wrong direction, and as it does so it moves ever closer and closer inward. Eventually, Triton will crash into Neptune!

I am a writer and astronomer whose articles have been published since 1981 in various journals, magazines, and newspapers. Although I have written on a variety of topics, I particularly love writing about astronomy because it gives me the opportunity to communicate to others the many wonders of my field. My first book, "Wisps, Ashes, and Smoke," will be published soon.