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Asteroid Crashes Likely Gave Earth Its Water
Diggester writes "Asteroids from the inner solar system are the most likely source of the majority of Earth's water, a new study suggests. The results contradict prevailing theories, which hold that most of our planet's water originated in the outer solar system and was delivered by comets or asteroids that coalesced beyond Jupiter's orbit, then migrated inward."
So rocks carrying massive amounts of water magically came to the Earth?
The four Elephants contributed a lot less.
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Hmmm.
Also it must have been hit by a whole heck of a lot of spacerocks, since 2/3rds of the surface is water. That's a lot of impacts.
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If this is true then how much water does the moon have? It seems like that should be estimable and relevant to the future if space travel if we assume all the earths water came during the late heavy bombardment. It also could be a good way to test this theory. If concentrations of water on the moon don't correlate wouldn't that poke some holes in the theory?
That's the simplest explanation. You nerds and your crazy ideas !!
Best possible explanation for unplanned pregnancies.
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If I was the creator of the universe, and had billions of trillions of planets capable of supporting life, what would be the most efficient 'delivery system' for me to use to deliver the "Seeds of Life" to them all?
If you can create universes, you don't need "delivery systems". You just speak your will into being.
Sheesh, evil *and* a jerk. -- Jade
Earth, in its early years, was a molten ball of rock and metal. Pretty much all the junk that's swirling around in the mantle today, plus the stuff in the crust that floated to the top. Think Jupiter's moon Io, but bigger, and it eventually cooled off. Anyway, when a planet is that hot, the water boils and becomes vapor.
Being that I am not an astronomer or astrophysicist, I'm not going to conjecture what really happened: but the theory goes that since Earth was too hot, water must have been delivered to it later on. Since asteroids are small and were freezing cold while Earth was super-hot, the theory goes that asteroids bombarded Earth and delivered water.
What I don't get is why would it not be possible for the water to have boiled off the surface, but floated to the top of whatever primordial atmosphere the Earth had? Or if no atmosphere, just hang out near the surface until things cooled off?
24 beers in a case, 24 hours in a day. Coincidence? I think not!
If you can create universes, you can pretty much deliver life any damn way you want to, I imagine. Who's gonna tell you no?
the heavier deuterium will wind up sinking into the part of the cloud that becomes part of the star
Though deriving from simple principles, it is not that simple- accretion happens in at least two distinct spatial scales: the loose, yet gravitationally bound 'cloud' (called an 'envelope') is feeding the accretion disk. This envelope's size is of the order of ten or twenty thousand Astronomical Units (1 AU = distance from Earth to Sun), and takes forever to 'collapse'; the accretion disk, in turn, is feeding the central object, is much denser, and things happen faster. Typical sizes for the accretion disk are a hundred or a thousand times smaller than the envelope (few tens to a couple of hundred AU).
Here is some nice imaging of an accretion disk.
How exactly all this happens is an active area of research. One of the things that give some insight on the stellar and planetary formation process is measuring relative isotopic ratios on things in space, and comparing them to terrestrial and Solar values. What Conel Alexander and company here have noticed here is that the D/H ratio of Earth's water is more similar to the one of some Carbonaceous Chondritic meteoritic material than it is to some comets.
The Carbonaceous Chondrites are dated to be old. Not the first solids of the Solar System, but still among the first. They were also deemed to never have been parts of a larger body: they were never, say, part of an ancient planet, and then broke-off: they formed as rocks (condencing out of gas and dust) somewhere and at some time in the accretion disk, early. Or so the story goes.
I guess a ranting point can be that there is this theory of the Late Heavy Bombarment: there are people in the community that believe the Late Heavy Bombardment was also the origin of Earth's and Mars' water oceans, that came from comets (which carry lots of water). But water in comets, as it is now, is different than the water of Earth's oceans in terms of its D/H ratio.
The three laws of thermodynamics:(1) You can't win. (2) You can't break even. (3) You can't even quit.
According to quick Google, average depth of oceans is about 4km, surface area of earth is about 510'072'000 km2 and water covers about 70% of earths surface.
5.1E8 km2 * 4km * 0.7 = 1.428 billion km3. Sphere of that volume is about 1396 km across.
The GP's graph says "1390 kilometres across and has a volume of 1.4 billion cubic kilometres", which is very close to that quick approximation.
My approximation is very quick and dirty (I didn't take into account that surface of earth is less 4km below the surface than on the surface, which would reduce the sphere... but I also didn't take into account glaciers, etc. which would increase the sphere... Obviously the surface of sea isn't exactly 70% and the depth isn't exactly 4km...) but I feel very confident that the scale of the number is about right and it happens to perfectly match the graph.
Reality and statistics says that there's a pretty good chance that an asteroid or comet strike big enough to potentially wipe out our species will happen again. If we are still around when it happens and we don't have sufficiently advanced space tech (either for colonizing other planets or for deflecting the comet/asteroid or both) then we certainly could be wiped out. Chances are miniscule that it will happen in our lifetimes, but if we manage to survive as a species for tens of millions more years, it's almost inevitable. It's possible that we might have sufficiently advanced terrestrial technology at that time to weather it, but our chances are even better if we have space capabilities. In other words, it's not a religious belief.
Also, what you say here still doesn't explain what the original comment has to do with The Fine Article despite the common theme of asteroid strikes. Why would narrowing down _which_ asteroids supplied most of Earth's water do anything to injure the idea that a massive comet or asteroid might cause another global extinction event in the future? You seem to be using some sort of faulty reasoning. Do you also think that because the ozone layer is a good thing that protects us that we should all make sure to breathe as much ozone as possible?
Where did the ice come from on the asteroids? Were they hit by little wet Earths?
As you must know (or maybe not) water is made of two hydrogen atoms and one oxygen atom. By mass, that means that oxygen is 16 parts oxygen and 2 parts hydrogen. Now, hydrogen is quite simply the most abundant element (from the regular periodic table anyway, who knows if any of the dark matter takes forms that could be classed as "elements") in the entire universe. As a single proton with a single electron, it's the simplest, most basic stable form of baryonic matter. As for the oxygen, it's estimated to be the third most common element in the universe (based on the numbers from spectrographic analysis of our galaxy). There's about 1/71st as much oxygen as hydrogen by mass, which means that there's about 1/1136th as many oxygen atoms as hydrogen atoms. As such, it's not hard for h2 molecules to encounter 02 molecules. When they do so energetically enough, you end up with water. Lots and lots and lots of water. A lot of it ends up mixed up in big celestial bodies, but plenty also accumulates into smaller objects like comets and asteroids. As for the origin of the oxygen, the prevailing and well supported theory is that it was mostly made in red giant stars where four helium (mostly made during the origin of the universe) atoms combined into one oxygen atom.
I don't see the rationale for arguing about water first being seeded in conditions that are mutually exclusive from those that develop a planetary mass on a particular orbit, nor do I see any argument compelling for this, it is another "plan 9" scape-goat (to use a religious term) that says "anything unexplained happened really far away, a really long time ago".
Also, to make things clear, this article isn't really talking about all of Earth's water, it's just talking about most of its surface water. Earth has plenty of other water entrained below the surface from its first formation, and some of the surface water was doubtlessly in the early atmosphere before the planet cooled enough for surface water.
Also "plan 9"? The one where humanoid aliens with really bad silver foil uniforms animate humanities dead (about three individuals worth) in order to take over the world? Ummm, huh?