On The Formation Of Suns And Their Planets
July 2, 2009
This will be a basic blog about the dawn of our solar system and how it came into being… Here I aim to tackle the dawnting process of accretion theory and, in doing so, demonstrate what a hostile environment a solar system can be during planet formation, and therefore, what an amazingly fortunate occurence it is that We i.e. all of life on Earth, are here, today, alive and well, basking in the warmth of our nearby by star, the Sun.
Just the other day… I was in a waiting room reading my way through a National Geographic in the line of time before my appointment. And I stumbled over the following article:
In some ways I was gob smacked when I read this i.e. that the super fine, almost particulate, lunar dust that, when touched with the bare hands would, permiate the epidermis so deeply you couldn’t get it out with a thousand washes… And it actually smelt like gun powder!!! How odd, I thought!? I mean, as the moon has no atmosphere, and basic laws of combustion require there to be a fuel and an oxidant present, how could there ever be any fire in the vacuum of space!? But then, when I thought back to my physics and astronomy 101, I realised that this was hardly surprising bearing in mind the forces that precipitated planet formation, and even star formation, as well as the undiluted Sun’s rays vigerously beating down over the long lunar days.
As we all know so well from looking at the amazing images from the hubble telescope… The Universe around us is littered with pockets of molecular and particulate clouds. As Professor Hal Levison from South West Research Institute once said, “It’s amazing when you really consider that all the planet’s in the solar system, the Earth and the rest of the rocky planets, the cores of the giant planets, Jupiter and Saturn, and the majority of the outer planets, Uranus, Neptune and Pluto, formed from material that is very fine pieces of dust… About the consistency or size of particles in cigarette smoke…” Pretty amazing stuff, that this super fine material actually makes up the planet that we’re now standing on… ??? I know… Total sci-fi! Forget about the parting of the Red Sea… This stuff is even stranger than fiction!
Thought fiction it is not… And to confirm this, in a recent BBC interview with Eugene Cernan, conducted for The Sky At Night’s celebration of “The Last Man On The Moon”, Commander Cernan mentioned that this super fine lunar dust just was just everywhere, being integral to making the moon’s surface appear the way it was seen i.e. smooth. “The surface (of the moon) was covered with dust. It’s like graphite. It’s a grey material and it penetrates everything. In places, it’s two or three meters deep… In other places, it’s just a film on top of the outcropping rocks… But it covers everything! It’s what makes the mountains, the big massifs that surrounded us, look somewhat smooth. But if you could blow away the lunar dust, it’d be very rugged outcrops.” So this dust… This space dust… The stuff that makes up stars and planets… Was pulled in by the moon’s gravity after the main bulk of the moon had accreted together, as the massive body drifted around with the Earth in its orbit, hoovering up the very last parts of the disk left… And as this dust left to moon, it accumulated on its surface, filling in all the gaps between the jagged rocky mass of the moon’s main bulk of a body… So simple and so elegant, when one thinks about it. And something that gives us a real insight into the accretion process, as first suggested by Victor Safronov, which confirms and allows us to see how planetary bodies are formed… Which has been preserved (thanks to a lack of atmosphere and weather on the moon) almost as meticulously as the time it finished… And when this is seen, it also allows us to see that the surface of the Earth is somewhat unusual too, in that most of the surface dust that might have been left like this, is now mixed up with water and moisture from out atmosphere, forming a “paste” or “mud” that Life managed to get a foothold in. Okay… Perhaps I’m racing away a bit… So let’s get back to basics.
Where did this dust come from???
Well… Let’s firstly, let’s take a brief look at where this dusty, nebulous material “supposedly” comes from…
Basically, it is said, and rightly so, that cosmology is the branch of physics that asks the grandest questions. After all, few questions within science can equal the impact of: “Where does the universe come from?” or “What is the fate of the universe” or “Where does the matter we are made of come from?”
But perhaps even more exciting than asking these questions is the fairly recent power that we have of answering them, at least partially, through a rational study of nature.
Most of us learned in high school that matter is made of atoms and that atoms are made of protons, neutrons and electrons. What we don’t usually learn in high school is that to each particle of matter there is another particle, an “anti-particle,” which is essentially the same as the particle but with opposite electric charge.
Thus, the negatively charged electron has its “anti-electron,” called a positron, which has positive electric charge; the proton has an anti-proton, and so on. Now comes the interesting part. According to the laws of particle physics, matter and antimatter should be present in the universe in equal amounts. And yet, we have ample observational evidence that, at least in a very large volume that surrounds us and extends far beyond our galaxy, there is much more matter than antimatter.
When particles collide with their anti-particles, the effects are devastating; they both disintegrate into electromagnetic radiation, their energy carried away in neutral particles called photons. In other words, if there were as much antimatter as matter in the universe, we wouldn’t be here to ask grand questions. The universe is somehow unbalanced, biased toward the existence of matter over antimatter. One of the greatest challenges in modern cosmology is to unveil the roots of this cosmic imperfection.
As with any scientific explanation, we need a few “basic ingredients,” a minimum amount of knowledge from which to build our models. The first ingredient we need is the Big Bang model of cosmology. According to this model, a small fraction of a second after the “beginning,” many kinds of particles and their anti-particles, in equal amounts, roamed about and collided with each other immersed in tremendous heat, as in a cosmic minestrone soup.
In the hot cosmic furnace of the Big Bang, many different types of particles were being cooked, not necessarily the familiar quarks (the constituents of protons and neutrons) or electrons. As the universe expanded and cooled, a sort of selection mechanism not only biased the creation of quarks and electrons over other types of particles, but also generated the excess number of particles over anti-particles. Surviving the annihilation with their antimatter cousins, these excess particles organized themselves into more complex structures, until eventually atoms, mostly hydrogen, were formed when the universe was about 300,000 years old.
But this is still a somewhat vague idea as to really what happened, as the particle physicists are still “out to lunch” formulating their theories about the creation of the universe, while CERN conducts ever more probing experiments into the nature of matter with the LHC, etc… So for the moment, the mystery as to how the mass in the universe came into being i.e. all this hydrogen, is above and beyond what the aim of this essay is all about.
So let’s return to the matter at hand… Namely that of the formation of stars and planets from nebula. These super fine clouds come in many forms, and are found abundantly throughout our Universe. And the two of the most commonly found types of these clouds are nebula and molecular clouds… Let’s take a look at an example of each:
1. Horsehead and Orion Nebule
This picture was taken from the APOD website, where the following expalnation was given:
“Adrift 1,500 light-years away in one of the night sky’s most recognizable constellations, the glowing Orion Nebula and the dark Horsehead Nebula are contrasting cosmic vistas. They appear in opposite corners of this stunning mosaic taken with a digital camera attached to a small telescope. The magnificent emission region, the Orion Nebula (aka M42), lies at the upper right of the picture. Immediately to its left is a prominent bluish reflection nebula sometimes called the Running Man. The Horsehead nebula appears as a dark cloud, a small silhouette notched against the long red glow at the lower left. Alnitak is the easternmost star in Orion’s belt and is seen as the brightest star to the left of the Horsehead. Below Alnitak is the Flame Nebula, with clouds of bright emission and dramatic dark dust lanes. Pervasive tendrils of glowing hydrogen gas are easily traced throughout the region in this deep field image of the same region.”
2. Molecular Cloud Barnard 68
Again, this picture was taken from the APOD website, where the following expalnation was given:
“Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. In fact, Barnard 68 itself has recently been found likely to collapse and form a new star system. It is possible to look right through the cloud in infrared light.”
These nebula (a word that is derived from the Latin word for “cloud”; pl. nebulae or nebulæ, with ligature or nebulas) are interstellar clouds of dust, hydrogen gas, helium gas and plasma. Originally nebula were a general name for any extended atronomical object, including galaxies beyond the Milky Way (some examples of the older usage survive; for example, the Andromeda Galaxy was referred to as the Andromeda Nebula before galaxies were discovered by Edwin Hubble). Nebulae often form star-forming regions, such as in the Eagle Nebula. This nebula is depicted in one of NASA‘s most famous images, the “Pillars of Creation“. In these regions the formations of gas, dust and other materials “clump” together to form larger masses, which attract further matter, and eventually will become big enough to form stars.
Below are some interesting ideas as to how this could occur:
Cue accretion theory… This happens as a cloud of gaseous material and dust contracts under the force of gravity. Spinning mass forms a disc, probably with a bulge at the centre where a warm protostar undertakes a gestation period. And then eventually the central region of this locality collapses under the hostile force of gravity, and allows the centre to continuously heat, as the ambient gases continue to gather toward its core, providing more mass and so more gravity. From then on, the protostar dispenses and radiates much of its heat and ejects matter outward from its polar regions, where the disc itself offers little restriction to this process. And during this period, a lot of the protostar’s dust and debris is removed toward the newly forming solar-system’s periphery. From there, fusion commences at the star’s core, and so the star begins its active nuclear life. And an interesting criteria for the commencement of active nuclear life is that, only stars that are 6 percent or more than our Sun’s mass can ever hope to attain the temperature and pressure in the core which is required to initiate fusion.
So… Just to touch base with this idea… What exactly is a star?
Stars are hot bodies of glowing gas that start their life in Nebulae. They vary in size, mass and temperature, diameters ranging from 450x smaller to over 1000x larger than that of the Sun. Masses range from a twentieth to over 50 solar masses and surface temperature can range from 3,000 degrees Celcius to over 50,000 degrees Celcius.
The colour of a star is determined by its temperature, the hottest stars are blue and the coolest stars are red. The Sun has a surface temperature of 5,500 degrees Celcius, its colour appears yellow.
The energy produced by the star is by nuclear fusion in the stars core. The brightness is measured in magnitude, the brighter the star the lower the magnitude goes down. There are two ways to measuring the brightness of a star, apparent magnitude is the brghtness seen from Earth, and absolute magnitude which is the brightness of a star seen from a standard distance of 10 parsecs (32.6 light years). Stars can be plotted on a graph using the Hertzsprung Russell Diagram.
So as we can see, there are small stars and larger stars, each having slightly different life cycels in relation to the speed at which they burn their fuel, some varience in life stages, and the color with which they shine… So lets take a look at the two main types of star.
1. Small Stars – The Life of a Star of about one Solar Mass.
Small stars have a mass upto one and a half times that of the Sun.
Stage 1 – Stars are born in a region of high density Nebula, and condenses into a huge globule of gas and dust and contracts under its own gravity. See images above of Nebulae.
Stage 2 – A region of condensing matter will begin to heat up and start to glow forming Protostars. If a protostar contains enough matter the central temperature reaches 15 million degrees centigrade.
Stage 3 – At this temperature, nuclear reactions in which hydrogen fuses to form helium can start.
Stage 4 – The star begins to release energy, stopping it from contracting even more and causes it to shine. It is now a Main Sequence Star. The nearest main sequence star to Earth is our Sun.
Stage 5 – A star of one solar mass remains in main sequence for about 10 billion years, until all of the hydrogen has fused to form helium.
Stage 6 – The helium core now starts to contract further and reactions begin to occur in a shell around the core.
Stage 7 – The core is hot enough for the helium to fuse to form carbon. The outer layers begin to expand, cool and shine less brightly. The expanding star is now called a Red Giant.
Stage 8 – The helium core runs out, and the outer layers drift of away from the core as a gaseous shell, this gas that surrounds the core is called a Planetary Nebula, as seen below.
Stage 9 – The remaining core (thats 80% of the original star’s mass) is now in its final stages. The core itself becomes a White Dwarf, and the star continues to cool and dim. When it stops shining altogether, the star effectively becomes a dead star, which is also known as a Black Dwarf.
Let’s just recap on that with this animation:
2. Massive Stars – The Life of a Star of about 10 Solar Masses
Massive stars have a mass of 3x times or more than that of the Sun. Some are even 50 times that of our own Sun’s mass!!! If these figures are proving slightly too abstract to visualize, the please do check out the following video (something that helped me visualize this a bit better):
So… Looking at the life stages of a massive star, we can observe the following:
Stage 1 – Massive stars evolve in a simlar way to a small stars until it reaches its main sequence stage (see small stars, stages 1-4). The stars shine steadily until the hydrogen has fused to form helium (it takes billions of years in a small star, but only millions in a massive star).
Stage 2 – The massive star then becomes a Red Supergiant and starts off with a helium core surrounded by a shell of cooling, expanding gas. The massive star is much, much bigger than a small star in its expanding stage.
Stage 3 – In the next million years a series of nuclear reactions occur forming different elements in shells around an ever progressively denser core, which is made up of iron.
Why iron? Well, if you really are curious about the physics behind this, and want to know more about how the various chemical elements that we use in our bodies came into being, then I’ll let Professor Jim Al-Khalili work his magic in this brilliant BBC documentary, entitled ATOM – The Key To The Cosmos (Part 2).
Stage 4 – The core collapses in less than a second, causing an explosion called a Supernova, in which a shock wave blows of the outer layers of the star off. (The actual supernova shines brighter than the entire galaxy for a short time). During a Supernova, any planetary system that the star might have had would be blown into atomic dust. Nothing would survive.
Stage 5 – Sometimes the core survives the explosion. If the surviving core is between 1.5 – 3 solar masses it contracts to become a tiny, very dense Neutron Star. If the core is much greater than 3 solar masses, the core usually contracts to become a Black Hole.
Again… Let’s have a quick recap with an animation:
So as you can see, there are marked differences in the way stars live out their lives, either as a wise old small star, eating his fuel in a slow and steady banquet of burning delight… OR as a greedy, headonistic, and perhaps even gluttonous massive star gorging themselves silly on whatever they have, as if there were no tomorrow.
An interesting thing about stars is (something that you saw in Professor Jim Al-Khalili documentary ATOM) that they are the forges for the heavier elements i.e. they fuse the basic matter of hyrogen and helium into heavier elements, going all the way up to iron (if in a massive star). Once iron is reached, it is really impossible for the star, no matter how large it is, to form heavier elements. However, once a massive star explodes in a Supernova, the forces and energies from this explosion are so violent and powerful that they actually fuse some of resulting heavier atoms already present (upto iron) together to make the heavier elements such as copper, zinc, silver, gold, lead, bismuth (oh, amazing bismuth), etc… So in essence, the more of these massive stars that there were in a region of space, the greater the proportion of heavier elements that will be found in the Nebula clouds of that region. Bearing in mind the probablity with which these stars occur, this data can in many ways give one an idea as to how old the universe might actually be. And bearing this in mind, astronomers “think” that the universe is about 14 to 15 billion years old. But I digress…
Once a star forms, then the dust cloud (that has been spun out into a disc surrounding the epicenter) either disappears entirely – OR – forms embryonic planets. Let’s take a look at a diagram showing this:
This daigram was borrowed from The University Of Oregon
It is during this period of planetoid formation that the solar system becomes a particularly dangerous and active construction site. Debris, basically made up of rocks, particluate dust, etc…, of all shapes and sizes slowly swirls around the star which is now burning brightly in the center. And as it spins around the star, so it languidly clumps together under it’s own gravitational pull over eons (to get the idea of how long, when a mass is small, it’s gravitational pull is very small too). But as these clumps get bigger and bigger, so they start to tug eachother with greater and greater gravitational forces. This slowly dislodges alot of the debris from their fixed orbits around the star, and sends them into somewhat chaotic orbital paths, whereby they swallow up other smaller debris, or either are swallowed up themselves by larger debris. As these collisions (which are very, very, very much more powerful than the most powerful of atomic weapon anyone has on this planet) go on, they start to produce ateroids, which in turn produce larger asteriods, and so on… Until after enough time, these cascading collisions eventually yield dwarf planets, and sometimes even planets.
This daigram was borrowed from The University Of Oregon
As you can imagine, these asteroid collisions are no longer in perfectly circular orbits… Rather they are tugging eachother further and further off a central and circular course, as the diagram above shows. Until eventually dwarf planets and planets orbit around our sun in off kilter, but none the less, stable (for some time period at least) orbits. Here I want to digress from the main theme of this blog for one moment, and retrace my steps back to a previous blog I wrote on strange attractors… No doubt, you can see how these orbits will exude a chaotic pattern of sorts, having be tugged and pulled and realligned so many times, that they now wobble with cycles that are simple rotations around the star, but also possess cycles within these rotations i.e. cycles of wobbles around the star. These inner cycles are no doubt in turn subtle and minutely modified/affected by the tugs of other planets as they align or pass near one another. Chaos’ hand is even at play with Earth’s orbital destiny, as Henri Poincare demonstrated in 1903.
But back onto theme… During this time of planetary formation… The colossal collisions that result between two bodies/asteroids slamming together at speeds in excess of 25,000 mph yeild so much energy and heat that the resulting unified body can often liquify into a molten mass, much like lava. So, in effect, these bodies will have a molten inner core and surface to them.This is something we commonly notice within planets such as the Earth, where we are not close enough to the Sun to melt our surface (as is the case with Mercury), and yet we have a liquid core of magma.
There is a current theory that a Mars sized planet smashed into the proto Earth and allowed the formation of our moon. During this impact, as hot silicate vapour surrounds the new planetary body, and slowly cools into solid particle disc. As these particles orbit around the new Earth, they too accret, giving rise to the lunar body we all know so well today.
Here I think it would be a good time to introduce a documentary that is narrated by Neil deGrasse Tyson for the “NOVA scienceNOW” series on PBS. It rather beautifully shows the immensely turbulent time that a planet goes through during its own formation.
But let’s forget about Life just for now… As you can see, Planetoids develop when matter swirling around an emerging star forms small pellets which collide and make larger bodies, we just called ‘Planetoids’. They coalesce at that point to form large planets with tracks of mostly empty space between them. And in the inner system, light gases are blown away by the star’s radiation to leave large rocky planets, and moons behind. To illustrate this I’ve borrowed the follwing diagram from NASA/JPL-Caltech.
This diagram compares our solar system to the Epsilon Eridani System which is just under 11 light years away from us. The caption that follows this diagram is as follows:
“This artist’s diagram compares the Epsilon Eridani system to our own solar system. The two systems are structured similarly, and both host asteroids (brown), comets (blue) and planets (white dots).
Epsilon Eridani is our closest known planetary system, located about 10 light-years away in the constellation Eridanus. Its central star is a younger, fainter version of our sun, and is about 800 million years old—about the same age of our solar system when life first took root on Earth.
Observations from NASA’s Spitzer Space Telescope show that the system hosts two asteroid belts, in addition to previously identified candidate planets and an outer comet ring.
Epsilon Eridani’s inner asteroid belt is located at about the same position as ours, approximately three astronomical units from its star (an astronomical unit is the distance between Earth and the sun.). The system’s second, denser belt lies at about the same place where Uranus orbits in our solar system, or 20 astronomical units from the star.
In the same way that Jupiter lies just outside our asteroid belt, shepherding its rocky debris into a ring, Epsilon Eridani is thought to have planets orbiting near the rims of its two belts. The first of these planets was identified in 2000 via the radial velocity technique. Called Epsilon Eridani b, it orbits at an average distance of 3.4 astronomical units—placing it just outside the system’s inner asteroid belt.
The second planet orbiting near the rim of the outer asteroid belt at 20 astronomical units was inferred when Spitzer discovered the belt.
A third planet might orbit in Epsilon Eridani at the inner edge of its outermost comet ring, which lies between 35 and 90 astronomical units. This planet was first hinted at in 1998 due to observed lumpiness in the comet ring.
The outer comet ring around Epsilon Eridani is denser than our comet ring, called the Kuiper belt, because the system is younger. Over time, Epsilon Eridani’s ring will become wispier like the Kuiper Belt. Its comets will collide with each other and break up, or get pushed out of the ring by the gravitational influences of planets.”
Here is a diagram that shows the layout and names of our own asteriodal belts:
“An illustration depicting the inner Solar System, from the Sun to Jupiter. Also includes the Main Asteroid Belt (the white donut-shaped cloud), the Hildas (the orange “triangle” just inside the orbit of Jupiter) and the Jovian Trojans (green). The group that leads Jupiter are called the “Greeks” and the trailing group are called the “Trojans” (Murray and Dermott, Solar System Dynamics, pg. 107).”
To give you an idea of just how similar (if somewhat smaller) these asteriods are to their dwarf planet and planet counterparts, I offer an interesting tidbit. Originally 243 Ida was discovered on 29 September 1884 by Johann Palisa and was named after a nymph from Greek mythology. Like all main-belt asteroids, Ida’s orbit lies between the planets Mars and Jupiter. Its orbital period around the Sun is 4.84 Earth years, and its rotation is 4.63 hours. Ida has an average diameter of 31.4 km (19.5 mi), and it is irregularly shaped and elongated, apparently composed of two large objects connected together in a shape reminiscent of a croissant. Apart from its surface being one of the most heavily cratered in the Solar System, featuring a wide variety of crater sizes and ages, on the 28 August 1993, when Ida was visited by the spacecraft Galileo, which was bound for Jupiter, a very interesting discovery was made… Apart from it being the second asteroid to be visited by a spacecraft, it was the first found to possess a satellite or moon!
Ida’s moon, Dactyl, was discovered by mission member Ann Harch in images returned from Galileo. It was named after creatures which inhabited Mount Ida in Greek mythology. Dactyl is about 20 times smaller than Ida, at a little more than a kilometer in diameter. Its orbit around Ida could not be determined with much accuracy. However, the constraints of possible orbits allowed a rough determination of Ida’s density, which revealed that it is depleted of metallic minerals. Dactyl and Ida share many characteristics, suggesting a common origin.
“This color picture is made from images taken by the imaging system on the Galileo spacecraft about 14 minutes before its closest approach to asteroid 243 Ida on August 28, 1993. The range from the spacecraft was about 10,500 kilometers (6,500 miles). The images used are from the sequence in which Ida’s moon was originally discovered; the moon is visible to the right of the asteroid.”
Dig it… “…its surface being one of the most heavily cratered in the Solar System…” Is it any wonder that many of the moons which are now cold and dead bear so many scars from their time of creation? Can you imagine all of the dust, debris, small asteriods, etc… that went crashing into their surface over the 4 billion year period that our solar system has been here? Certainly enough to clear up most of the inner solar system and outer solar system.
And the abundance of crater riddled surfaces is something that very much astonished the Voyager 2 team when they visited the outer planets and looked at their moons.
I’m going to easily mention more than five other objects that bear the marks of creation on their surface for all to see without even straining. And there are many more besides this in our solar system.
“Color differences on Mercury are subtle, but they reveal important information about the nature of the planet’s surface material. A number of bright spots with a bluish tinge are visible in this image. These are relatively recent impact craters. Some of the bright craters have bright streaks (called “rays” by planetary scientists) emanating from them. Bright features such as these are caused by the presence of freshly crushed rock material that was excavated and deposited during the highly energetic collision of a meteoroid with Mercury to form an impact crater. The large circular light-colored area in the upper right of the image is the interior of the Caloris basin. Mariner 10 viewed only the eastern (right) portion of this enormous impact basin, under lighting conditions that emphasized shadows and elevation differences rather than brightness and color differences. MESSENGER has revealed that Caloris is filled with smooth plains that are brighter than the surrounding terrain, hinting at a compositional contrast between these geologic units. The interior of Caloris also harbors several unusual dark-rimmed craters, which are visible in this image. The MESSENGER science team is working with the 11-color images in order to gain a better understanding of what minerals are present in these rocks of Mercury’s crust.
The diameter of Mercury is about 4880 kilometers (3030 miles). The image spatial resolution is about 2.5 kilometers per pixel (1.6 miles/pixel). The WAC departure mosaic sequence was executed by the spacecraft from approximately 19:45 to 19:56 UTC on January 14, 2008, when the spacecraft was moving from a distance of roughly 12,800 to 16,700 km (7954 to 10377 miles) from the surface of Mercury.”
2. Earth’s moon
“Full Moon view from earth, taken in Belgium.”
3. The moons of Mars
“The High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter took two images of the larger of Mars’ two moons, Phobos, within 10 minutes of each other on March 23, 2008. This is the first, taken from a distance of about 6,800 kilometers (about 4,200 miles). It is presented in color by combining data from the camera’s blue-green, red, and near-infared channels.
The illuminated part of Phobos seen in the images is about 21 kilometers (13 miles) across. The most prominent feature in the images is the large crater Stickney in the lower right. With a diameter of 9 kilometers (5.6 miles), it is the largest feature on Phobos.
The color data accentuate details not apparent in black-and-white images. For example, materials near the rim of Stickney appear bluer than the rest of Phobos. Based on analogy with materials on our own moon, this could mean this surface is fresher, and therefore younger, than other parts of Phobos.
A series of troughs and crater chains is obvious on other parts of the moon. Although many appear radial to Stickney in this image, recent studies from the European Space Agency’s Mars Express orbiter indicate that they are not related to Stickney. Instead, they may have formed when material ejected from impacts on Mars later collided with Phobos. The lineated textures on the walls of Stickney and other large craters are landslides formed from materials falling into the crater interiors in the weak Phobos gravity (less than one one-thousandth of the gravity on Earth).”
“Enchanced-color image of Deimos, a moon of Mars, captured by the HiRISE instrument on the Mars Reconnaissance Orbiter on 21 Feb 2009.”
4. Jupiter’s moon Callisto
“Bright scars on a darker surface testify to a long history of impacts on Jupiter’s moon Callisto in this image of Callisto from NASA’s Galileo spacecraft. The picture, taken in May 2001, is the only complete global color image of Callisto obtained by Galileo, which has been orbiting Jupiter since December 1995. Of Jupiter’s four largest moons, Callisto orbits farthest from the giant planet.”
5. Two moons of Saturn
“What has happened to Saturn’s moon Iapetus? A strange ridge crosses the moon near the equator, visible near the bottom of the above image, making Iapetus appear similar to the pit of a peach. Half of Iapetus is so dark that it can nearly disappear when viewed from Earth. Recent observations show that the degree of darkness of the terrain is strangely uniform, like a dark coating was somehow recently applied to an ancient and highly cratered surface. The other half of Iapetus is relatively bright but oddly covered with long and thin streaks of dark. A 400-kilometer wide impact basin is visible near the image center, delineated by deep scarps that drop sharply to the crater floor. The above image was taken by the Saturn-orbiting Cassini spacecraft during a flyby of Iapetus at the end of 2004.”
Hell! There are even 150 impact craters that can still be seen here on Earth!!! Let’s look at five of the most obvious:
I think you’re beginning to get the idea now… That these celestial bodies (which have had their surfaces preserved since their creation i.e. because they are free from weather erosion, geothermal activity, tectonics, etc…) are riddled with a history of immense bombardment from debris during their creation. Even those planets and moons that apparently have little or no trace of this bombardment left (due to surface erosion, weather conditions and tectonic movement) were still battered just as much when they were young. In fact, the larger a dwarf planet or planet becomes, the greater the gravitational pull of its mass, and so the more bombardment it is likely to receive. It’s almost as if they gobble up as much as they can the bigger they get. And, to get a real perspective on the down pour of debris, you have bear in mind… Most of these immense impacts would have been enough to seriously disrupt life on Earth, if not extinguish it totally… If it was around back then, that is. I mean… A sizeable impact, if from a big enough asteriod that is travelling fast enough, could hit the atmosphere and blow most of it off into space… And when it fuses into the Earth, the energy could liquify the Earth’s land into one big molten rock all over again, or maybe even shear it into two separate pieces. So when you think about what those astronauts discovered i.e. that moon dust smelt like burnt gunpowder… I mean… It’s not really any surprise, what with all those impacts yielding so much energy, and then all the dust being blasted daily by the direct rays of the Sun!!!
As you can see… The solar system was quite a brutal place when it was forming… So, for us to have come about is quite an improbable event, when you think about. One tug to many from its near neaighbors and the Earth would/could go sailing off into the Sun OR off into outerspace.
Apparently for solar systems to form in the way that ours did i.e. with the 8 planets and various dwarf planets, is a highly improbable event!!! HIGHLY IMPROBABLE… And then, as if all that improbabilty wasn’t enough… That solar wind that blew away all the remaining gas and dust, which was left lying around after accretion, out towards the edges of the solar system… A solar wind consisting of electrons and ions, which travels out from the sun in all directions at speeds of more than 500 kilometres per second… A wind that can char the suface of a planet and leave most organic matter exposed to its powerful glare simply a frazzelled piece of carbon… Well. It doesn’t just stop at blowing away particulate dust, let me tell you. It does equally as good a job of blowing off atmospheres from planets too. But… Would you believe… Thanks to the fact that we have a magnetic field around our Earth, our atmosphere is portected! And so life the Earth’s surface are spared the full brunt of harmful solar rays. Rays that have irraditated the lunar dust for over four billions years, leaving it smelling like gun powder, as Eugene Cernan smell after his lunar landing.
“So what?” I hear some of you say… Well. Mercury, Venus, Mars and Pluto, all fairly small, low gravity planets much like the Earth, have no magnetic field to buffer the Sun’s solar winds. In fact, when Voyage 2 turned around to look at the planets, it could see streaks of their atmospheres being blown off in these solar winds. And when we’ve looked at the suface of these planets, they too are parched, ionised and burnt. So what would we do without the Earth’s magnetic field? Fry basically…
And then… As if to add more to the equation. There’s the question of chemical proportions and compositions… On the Earth’s moon they found that nearly all the lunar rocks studied were depleted in volatiles (such as postassium or sodium) and were completely lacking in the minerals found in Earth’s water. But here on Earth… It just so happens that we have all the right elements, in the right proportions AND with the right conditions… Something that was AMAZINGLY fortunate to kick start Life off. Yes… Just the right conditions!!! You know when you hear others moan about it raining, or it being too hot… Well. The Earth is currently orbiting on average (as we have seen the Earth does NOT orbit in a perfect circle around out star) at about 150 million km away from the Sun. But… If the Earth had been tugged another 10,000,000 km outwards, it would be harshly cold most of the time… Or if it was another 10,000,000 km closer to the Sun, it would be a lot hotter. So… During that chaotic time (where the odds were stacked so high against us being where we are in our solar orbit), a time of accretion for all the bodies in the solar system, it’s near on a divine miracle that we are here now, right in the sweet spot of the temperate ranges suitable for optimum life.
No doubt the habitable zone would fluctuate depending on the star’s type and size. Massive stars would expend much more heat and so a planet that might harbor life would have to be much further away from it’s sun. And if orbiting further away, it would mean longer years, where winters on a planet with a tilted axis (like Earth’s own) might stretch on for up to five Earth years. Who knows how this would affect the life on the planet i.e. whether it would be as vibrant and diverse as our own, or only able to support the most hardy organisms that might need to hibernate for those five bitterly cold Earth years.
And then there are issues to consider relating to the size of the planetary systems star… Larger stars burn for half as long… Or even much less than half as long. So would this shorter time period allow Life on a planet harbouring it to evolve into something like ourselves i.e. sentient and intelligent beings? Or would it go to Supernova before this evolutionary leap could happen, and so destroy all the solar system’s Life forms?
Just one last thing that I will mention here… As a tribute to their blanket of strong gravitational fields that protect us by lowering the probability that we will get hit by any accretion debris still traversing the solar system… Are the four… YES! Not one, or two, nore three… But four gaseous giants of Jupiter, Saturn, Uranus and Neptune. With out these, there would be a much, much higher incidence of space debris colliding with the Earth causing mass extinctions on a global scale a lot more frequently than they currently do occur. Basically each collision with an object of 1 km in diameter would be like a reset button for Life. So… A BIG, EXTRA MASSIVE BIG UP to the gaseous giants!!! “What the hell does mean?” Well… Wasn’t that one of the most amazing sights when Jupiter caught Comet Shoemaker-Levy 9 – that rouge comet that was shooting in and out of our solar system (as comets do)?
“Comet Shoemaker-Levy 9 (SL9, formally designated D/1993 F2) was a comet that collided with Jupiter in 1994, providing the first direct observation of an extraterrestrial collision of solar system objects . This generated a large amount of coverage in the popular media, and SL9 was closely observed by astronomers worldwide. The collision provided new information about Jupiter and highlighted its role in reducing space debris in the inner solar system.”
This was a prime example of how the planets were built… That July, Jupiter grew that little bit extra, and its gravitational pull got that little bit stronger…
So… Bearing ALL of that in mind. Just how fortunate do you think we are that we are now here??? Forget you winning every lottery ever… And forget the money that would come from winning every lottery in every country since the idea of a lottery started up. The figures and odds on this one are way, way, way more stacked against us. This experience of Life that we have going on here is FUCKING PRICELESS!!! You are some of the most fortunate atoms in the Universe… Some of the most fortunate pieces of star dust to walk a planet, to be given Life! You have come through ALL odds… And you are standing in the temperate zone of a solar system, who’s initial conditions were WAY MORE destructive than all the atomic wars we could have waged by now. And… You are now reading this… A token to that huge mountain of improbability. So now you are here, standing on its summit, savouring and enjoying this awesome view… Don’t you ever, EVER DARE forget it. Cause it’s a dark, harsh, inky black void of a desolate space off this planet… One that, if you ventured into it, it would make you realize just how amazingly beautiful and hospitable a place the Earth truly is.
But hell… What would I know!?!? Even though I can write about all of this, it still doesn’t compare to what it’s actually like out there… I mean, who could talk about it any better than those who actually left the Earth to fly to the moon? So I’d like to bring your attention to an amazing film that was made recently…
If you are enthralled by this and want to know more… More about what processes brought you, Life and the Earth and planets into being… Then please do yourself a favour, and check out the BBC’s documentary called “The Planets.” It’ll bring you closer to home about what a fortunate being you truly are. Hell… Let’s push the boat out. What fortunate beings we all truly are!
And if you still need more (heaven forbid)… Then also check out Bill Bryson’s “A Short History Of Nearly Everything.” Then maybe… Just maybe, you might be getting a good idea about the bigger picture of things, and how STUPIDLY damn imporbable it is that you are here, reading this now…
After all that… If you have grasped just how fortunate you really are… Then do yourself a favour and look at what you’re doing with your life… And why you’re doing it. Because, when you know how rare and improbable we all really are, then it really does become a wonder why many of us numb ourselves with consumerist needs/habits/modes of out dated thinking… I mean, WAR… Why? Poverty… Why? Greed… Why? Because when you are standing in the garden of Eden, having seen the partched empty deserts of the moon and other planets… And you TRULY know that this is an immensely fortunate occurence, that we are all standing here becoming aware of who and what we really are, you should ask yourself… Very seriously and very honestly… “ARE YOU FUNCTIONING PROPERLY???” Because if someone gave you the blue prints on how to make a wooden chopping board when needed to mend your motorbike… How the fuck are you going to do a proper job? When you’re given the garden of Eden, a glistening pearl filled with various lifeforms in the infinite black void of space and time… Which has limited resources… Where all life, weather, and other phenomena are interlinked in a highly sensitive cascade of interconnected chaotic cycles, habits and variences, almost all of which are centered around far too many “strange attractor” basins to even begin to imagine… Forging phase space patterns, the likes of which only “God” has seen… How do you think you are going to affect this garden while looking at the world through the eyes of the blinkered consumerist mode of money and self centeredness… Positively… OR detrimentally… I mean… If you think the motor bike is like a chopping board… Would you be treating it correctly? THINK ABOUT IT!
“Although gold dust is precious, when it gets in your eyes, it obstructs your vision.”