Slashdot Mirror
Planet Crash That Made Moon Left Key Elements For Life On Earth, Scientists Say
Scientists are claiming the cosmic collision that made the moon left a host of elements behind on Earth that were crucial for life to emerge. The Guardian reports: The impact 4.4 billion years ago is thought to have occurred when an itinerant planet the size of Mars slammed into the fledgling Earth, scattering a shower of rocks into space. The debris later coalesced into the moon. Beyond an act that shaped the sky, the smash-up transferred essential elements to the Earth's surface, meaning that most of the carbon and nitrogen that makes up our bodies probably came from the passing planet, the researchers believe.
Petrologists at Rice University in Texas reached their conclusions after running experiments on geochemical reactions under the high temperatures and pressures found deep inside a planet. They wanted to understand whether Earth acquired key elements from meteorites that slammed into Earth or through some other ancient route. Lead author Damanveer Grewal found that a planet with a sulphur-rich core would have large fractions of carbon and nitrogen on its surface. Such a planet could transfer that volatile material to Earth in just the right proportions if it happened to clatter into it, the researchers found, after modeling a billion different cosmic scenarios in a computer and comparing them to conditions seen in the solar system today. The research is published in Science Advances.
Petrologists at Rice University in Texas reached their conclusions after running experiments on geochemical reactions under the high temperatures and pressures found deep inside a planet. They wanted to understand whether Earth acquired key elements from meteorites that slammed into Earth or through some other ancient route. Lead author Damanveer Grewal found that a planet with a sulphur-rich core would have large fractions of carbon and nitrogen on its surface. Such a planet could transfer that volatile material to Earth in just the right proportions if it happened to clatter into it, the researchers found, after modeling a billion different cosmic scenarios in a computer and comparing them to conditions seen in the solar system today. The research is published in Science Advances.
If such collisions are rare, a possible explanation for the Fermi paradox is that life is so rare that we may be the firsrt.
No need for things like intelligence almost always self-destroys, etc.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
The Giant Impact Hypothesis became popular with the experts because it explained why the compositions of the Earth an Moon are so similar. The major problem with it (at the time) was such a collision would blast an enormous amount of the planets into an orbiting cloud of debris and a whole lot of the lighter elements and compounds (like water) would be lost to space. It's estimated that such a collision would heat Earth's surface to over 500 C, maybe over 1000C. It would "only" take 50 or 100 million years (maybe less) to cool and the debris cloud wouldn't be stable for long. I don't understand why, but that's what they say. So, they're left with a primordial heating as it coalesces/compresses (also some radioactive heating) and some cooling then the impact and whoops, so long atmosphere, so long water! So, thats why theres so much interest in missions to asteroids and comets, we are trying to get evidence showing which (if either) of those types of things "re-fertilized" the surface here with water. I don't recall where I read it but for at least hundreds of years after the collision, the debris would rain down on the Earth like Zeus's wrath. (or maybe Vulkan). The atmosphere would be unsurvivable until the bombardment mostly stopped. One of the puzzles about Earth's surface is why there are so many heavier elements on it. When it was molten, the heavier elements should have sunk down to the core (or mantle) and all the fun stuff (Iron, Copper, Zinc, Silver, Gold, Titanium, Uranium...) would only be present in closer to trace amounts. So, IF the collision with Theia happened, and IF Theia (or Earth) had enough "inner" stuff blasted into space, it dropping back down onto the surface is one possible explanation. The GIE fits the best of all the ideas but it does have some critics and they do have evidence which seems to suggest it is wrong. The problem is that the GIE is "tuned" in terms of when it happened - since it had to be before life appeared (maybe 3.4 billion years ago (bya) (although some evidence pegs the first evidence (not fossils, but isotopic 'signatures' of biocarbon in zircons) at over 4 bya. The hypothesis should be taken with a huge grain of salt; it may be right or it may not. Usually for a 'popular' idea to go dark, the evidence against it builds up and eventually no one who isn't a "true believer" finds its explanatory power credible. So far, that's not happened with the GIE, so it's not in trouble. But it is just one of the ideas floating around. Also the "need" for the heavy metals and carbon is because the geological carbon cycle removes it from the surface. (although plate tectonics is believed to not exist 4+bya, so I have to ask: ok, so its been ~4.5 billion years since the GIE, and carbon is still around. So, what was different before it that would cause the giant sucking sound and 'eat' all the carbon which isn't happening today? 4.6-4.3 bya is ~300 million years and it's been 10 times that since the GIE (hypothetically) - explain the enormous difference. All I can guess is that the molten newborn Earth must have acted differently than the hot surface right after the GIE. I'm not sure I buy it. Its like the studies which use heavy metal catalysts for synthetic abiogenesis, The hypothesis required metal catalysts, and they should have been relatively rare on the surface, so how do you explain them being then. There's way too much hand-waving for me to have any confidence that they're probably on the right track, but at least fleshing out the model gives it an ever increasing target to take pot-shots at.