Our last installment I learned y’all about where the existence of everything came from. This time around you get to know how rocks condense out of clouds of gas spiriting around outer space, how they get stuck together, what they are made of, and how they made the Earth!
After gigantic, spectacular, awe-inspiring, neighborhood-killing supernovae explosions, the blast waves can expand from the epicenter at rates of speed close to 40% the speed of light. This is really, really fast! When these insanely speedy blast waves bonk into the aimless clouds of hydrogen and helium in the galaxy the clouds get compressed. This compression can be the catalyst for the formation of a new star. If you remember last post (http://noospheregeologic.com/blog/2013/02/16/the-rare-gem-series-meteorites-part-one-the-big-bang-to-supernovae/), when a large interstellar cloud is compressed it can begin to collapse thanks to its new, denser center of gravity. The cloud contracts even further as it begins its journey to becoming a star.
For the first few million years after the star inside the cloud begins to fuse hydrogen and enter the main sequence of its life cycle, it’s not very bright thanks to all the dust and debris obscuring the light of the young star. Both the cloud and the star inside are rotating much like a figure skater who pulls in their arms to spin faster. As the cloud collapses it begins to spin faster and faster (when the core of a supernova collapses into a black hole or a neutron star it can be spinning at several (hundred? thousand?) times a second!). This orbiting debris around the dim new star can crash and smash into each other on the atomic and molecular level sticking together thanks to static electricity. Think of the atoms like a bunch of socks and fleece pullovers in the dryer colliding and sticking while continuing their orbit of the star. When enough bits get stuck together (well, a lot of bits) they can begin to have enough mass to attract other atoms, molecules, and bits of matter. These hunks of matter are what we call ‘asteroids’ and if they got big enough, ‘protoplanets’.
Protoplanets are like Rumba robot vacuum cleaners blindly going around the solar system sucking up debris. These protoplanets were originally comets and asteroids as they clear a swath around the stars cloud and eventually the biggest chuck of rock in a particular orbit monopolized gravity and started to absorb anything in it’s reach. One of the definitions of a planet is an object that “sweeps its orbit” of all the dust and debris and incorporates it into its planet (the other two main rules for a planet: must be rounded, and must orbit in the plane of the solar system). The Earth began dominating its region of the solar system and clearing its orbit somewhere around 4.4 billion years ago
When an interstellar cloud collapses, and begins to spin, the big blobby cloud will flatten out, like a disk of pizza dough spinning through the air, condensing the cloud adding to the material being swept clean by the protoplanets.
As the protoplanets clear the area around the new star more light begins to shine throughout the star system. The hot and energetic solar winds begin to blow the lighter material into the further reaches of the solar system concentrating large swaths of hydrogen and helium far away. This is why we have the gas giants like Jupiter, Saturn, Uranus, and Neptune all 500 million or more miles from the Sun. Out at these distances the light particles lose much of their energy and find themselves trapped gravitationally much more easily to nearby objects.
Closer to a newborn star we find rocks condensing where it is too hot for ice or gas to still exist. Rocks are made of heavy things like silica, iron, aluminum, zinc, and other metals (astronomers refer to anything heavier than helium as “metals”… I think it’s just to piss of chemists), stuff that is too heavy for solar winds to push out into the far reaches of the star system. We all know that it can take a few thousand degrees to melt metal or a rock, and only a couple hundred degrees to melt something like water or to sublimate carbon dioxide, right? Well, space knows this too, and while it may be completely inhospitable only a few million miles from a star, it is cool enough that things like iron, nickel, silica, and aluminum will no longer be gas (even though it may be 1000 degrees or more). This is why we find rocky planets near the sun like Mercury, Venus, Earth, and Mars. It’s so warm that most of the lighter particles energetically vibrate away from the strong pull of gravity generated by these small planets and then get blown far away by the solar winds.
It’s also true that the closer a planet is to the Sun, the larger the percentage of it will be comprised of iron and nickel, and don’t have much in the way of water, methane, CO2, or ammonia (which are largely made up of lighter elements than the stuff of rocks). Planets like Earth most likely got most of its atmosphere and water from the impacts of comets.
The solar winds are constant. As long as there is fabulous radiation produced by the nuclear reactions inside a star (or in our case, the Sun), small particles will have a constant force acting upon them trying to push them further and further way from the star. Into the farthest reaches of the solar system they go. Since all the dense atoms are solidifying not too far from the star itself they begin to randomly bonk into each other. Many of these particles have been stripped of electrons and when they clumsily run into a counter part they can stick statically like a sock to a sweater in the drier. If enough of these particles being to stick to each other the begin to actually draw in other atoms and small clumps of matter to them via gravity. The solar system has just made it’s first asteroids and proto-planets!
As for all the light bits of matter that are kicked out of the inner circle and sent to the great beyond, they too begin to cool off once they reach a zone where the light from the star is too weak. Water, ammonia, and CO2 will begin to freeze and form their own chucks of ice balls. These too can become large enough to start to attract wayward particles via gravity. Out at this distance from the star, loose atoms of hydrogen and helium do not have the energy to escape anything that is large in mass. As these balls of ice smash into more balls of ice they too begin to form proto-planets. When the proto-planets are big enough an ever-thickening atmosphere comprised of hydrogen and helium begins to form. These are the gas giant planets with Jupiter as their king. Any planets that formed beyond the asteroid belt were formed beyond what scientists call the “Frost Line”. Any closer and their constituent materials melt.
The early solar system is a violent, violent place. Rocks hurtling in random vectors at speeds beyond 100,000 MPH can obliviously smash into each other in outrageous explosions; their obliterated remnants quickly coalescing into a new celestial body drawn into the center of their collective mass. Soon, at varying distances out from the star, alpha proto-planets begin to appear. These large rocky or icy bodies begin to “sweep” their orbits clean; meaning, anything smaller than the proto-planet gets “sucked” in via immense gravitational pull.
When the proto-planet is about 500 kilometers across (~300 miles) gravity begins to round it into a sphere. For an early solar system this period of violence can last billions of years. In our own solar system the Sun started out with maybe only 2% of the gas cloud it formed from comprised of something other than hydrogen or helium. This means that the heavy elements that condensed near the Sun to form the rocky inner planets didn’t really have that much material to work with. For the outer planets this means the opposite was true as there is way more volatile material rich with hydrogen and bits of helium that got blown to the outer solar system by solar winds. Thus, the inner planets are rocky and small while the outer planets are gassy and ginormous.
Early Earth was hell. Literally hell on Earth. Imagine a barren sphere whose surface is comprised entirely of hundreds of millions of square miles of boiling lava. There is no discernible atmosphere beyond the thin wisps of fart-smelling vapor pooped out by bubbles of gas of the churning oceans of lava. This is the Earth of about 4.55 billion years ago. Every few hours a new rock from space the size of a city smashes into the surface at tens of thousands of miles per hour with enough force to vaporize solid rock into gas creating yet another reason the surface is molten.
This goo-ball Earth is just a big jiggly mess, its gravity constantly inviting trouble upon its surface. There is one advantage to being a hellacious ball of goo: differentiation.
Differentiation is when heavy stuff sinks and light stuff floats. We have all see it work with a rock and piece of wood in some water, but what about with lava? Here is a fun experiment to try: If you have two ping pong balls and you place them at the bottom of a jar, then pour sand over them they will stay at the bottom of the pile of sand, right? Same thing if you then place two steel balls on the top of the sand, those balls aren’t going to go anywhere. What if you added energy to the jar? Say you could put a vibrator to the jar and make the sand jiggle much like how atoms in a liquid would jiggle. Two things will happen; the steel balls will vanish into the sand and the ping pong balls will suddenly appear at the surface! The early Earth was in a constant state of fluidization since it was a giant ball of liquid. The heavy metals began sinking toward the Earth’s core and the lighter materials began to float toward the surface. This is why today the surface of the Earth is rocky and about 3.5 grams per cubic centimeter in density, while the Earth’s core is metal and about 12.5 grams per cubic centimeter.
Differentiation also meant that light fluffy volatiles like CO2, oxygen, nitrogen, water, etc… that somehow found themselves weirdly trapped inside of early Earth, and not blasted into the deeper reaches of the solar system, rose to the surface. Earth began building a very crappy atmosphere. Way to go, Earth.
Oops, I spoke too soon. Somewhere between 4.5 billion and 4.25 billion years ago the Earth got into an accident. A planetoid (a fellow proto-planet) got thrown off course, probably by a larger body like Jupiter acting like a gravitational slingshot, and crossed the Earth’s path. This planetoid is likely to have been about the size of Mars (about 10% of the Mass of today’s Earth) and the two decided to engage in a hostile merger. The collision was so large as to be essentially unexplainable in comprehendible magnitude. Both planets (if there was any solid features between them) instantly vaporized most of their constituent material. Much of the Earth’s crustal material splattered into space resulting in billions of new pieces of rock that would rain back down on the Earth’s surface further liquefying the young injured planet. About 1/80th of the mass of Earth stayed in orbit above the Earth and eventually coalesced into what we know as the Moon. The Moon is not very dense and is about 3.5 grams per cubic centimeter; meaning it has about the same density as the Earth’s surface. This is the largest telltale sign that the Moon was born of the Earth. All rocky bodies in the inner solar system are denser than the Moon. If the Moon had been a captured body that wandered near the Earth’s gravitational field, it would more than likely be denser with a larger metallic core.
Many of these early proto-planets and planetoids that were quickly maturing throughout the solar system also differentiated. Many of these objects were blasted apart by collisions. This leaves us with four basic kinds of materials that smash into objects in the solar system today (I am being very hand-wavy and leaving out lots of details that will be explained in Part III):
1) Ancient “first” rocks. These are the asteroids that first condensed out of the cloud from which our Sun and solar system was born (scientists refer to them as “chondrites”.
2) Differentiated rocky material. These are rocks of igneous nature that are the bits of surface of near by moons and planets, or the blasted apart surface material of obliterated planetoids.
3) Differentiated metallic material (more commonly referred to as “iron-nickel” asteroids. When a differentiated planetoid is blasted apart due to a collision this is the remaining core material.
4) Comets. Balls of ice from much deeper out in the solar system. The most common prevailing hypothesis ties comet impacts to the source of most of the Earth’s water and atmosphere. Since the European Space Agency’s successful landing of the Rosetta probe on the Comet 67P/Churyumov-Gerasimenko this hypothesis has been turned on its head. Rosetta drilled into the comet and discovered that the ice material is different isotopically from the majority of the material found on Earth. Oh, science!
The odds of the Earth experiencing another mass extinction via a comet of meteor impact is 100%. What we cannot predict with any statistical certainty is if this will occur while humans are still alive. In lieu of significance in our probabilities we instead turn to hard data by mapping our solar system and charting the orbits of every object we have ever seen. At the moment astronomers are aware of, and are mapping, about half a million objects that are known to cross the Earth’s orbit. These objects are important for two reasons: One, they have the potential of ending our species; and two, they could be worth trillions of dollars.
Remember those iron-nickel asteroids? Yeah, just one of those little guys can potentially be worth more than all of the human productivity in our entire history. Here is how it works: A planetoid is at one time a bubbling, boiling mass of magma and lava. All the heavy metallic elements are sinking toward the core, and all of the light rocky material is floating toward the surface. Then some other asshole jerk-of-an-asteroid/planetoid collides with our differentiating body and explodes the whole thing to kingdom come. Now chunks of differentiated core is floating around space just chock full of base metals like iron, nickel, copper, zinc, etc… as well as really heavy precious metals like gold, platinum, uranium, rhodium, palladium, and so on…
One iron-nickel asteroid a mile in diameter has, in just precious metal, $4-5 trillion dollars in material. Why are we wasting our time planning missions to stupid fucking useless Mars when there are trillions of dollars to be made off of space rocks? I have no clue. Fortunately there are a few eccentric billionaires like Elon Musk and Richard Branson who see things my way, and they are investing large portions of their fortunes into space exploration companies like SpaceX and Planetary Resources.
Mining space has a couple of benefits. Chief among these is that we would have no need to ever mine the Earth for metals ever again. A huge source of pollution and environmental degradation gone! The drawback? How do we do it? Do we capture an asteroid into our orbit and mine it from there utilizing something like a space elevator? If so, how do we capture it without accidently killing everything on Earth when we make a wrong calculation and miss our target and instead hit the Earth’s surface?
Every thing has a risk and reward, I suppose.
Next time join me for Part III and learn about how often meteors hit us, where we can find them, how we can find them, what you can sell them for, and why they love Russian dash cameras so much!
