I guess it's possible
But I think to confirm for sure, they should really be checking the fossil records for evidence of the superpowers that these sharks developed.
A gigantic supernova explosion may have triggered mass extinctions for creatures living in Earth’s prehistoric oceans some 2.6 million years ago, according to new research published in Astrobiology. Marine animals like the megalodon, a fearsome shark around 10.5 meters (34 ft) long and with huge jaws full of sharp, pointy …
I thought water was supposed to be an excellent protector against radiation? So was there something special about this particular radiation event (or were the levels just so high) that they negated the protective qualities of the water?
If this was a mass extinction of land animals I'd believe it in a second, but under water, hmmm. The figure I've found online is that you halve the level of radiation for every 7cm of water it passes through. To kill off underwater creatures that dont need to surface (like whales and dolphins), that must have been one hell of a radiation event, wouldnt it?
High energy muons are remarkably slippery and can pass a kilometer of water without to much trouble. The same thing applies to the ability to pass through a human, megalodon or whale though so I have no clue about how much energy are dumped into a nearby dna molecule when the muon zips by.
I think we can safely ignore the neutrinos though as you have to be inside the surface of the star to recieve a lethal dose of neutrino radiation from the supernova and unless the megalodons were surfing on the stars hitchhikers guide to the galaxy style they were probably not in any danger in that regard.!
There's more than one kind of radiation, with very different penetrating properties; in this case muons, which are massive and very penetrating, are produced by the interaction of cosmic rays with matter.
Incidentally whales and dolphins are sea creatures which do need to surface, to breathe!
"The radiation wouldn't need to go far through water. If iron-60 is dropping into the water and getting into the food chain, it would then emit the radiation whenever an atom decays - getting whatever happens to be local at that point."
Very nice, but a lot of people here are overlooking the minor detail that most living organisms and especially the somewhat larger ones have red blood with hemoglobin, which derives its characteristic colour and oxygen transporting abilities from the embedded iron atom. Thus most of these organisms are quite efficient in taking in any iron available, including radioactive iron-60. This will quickly accumulate in larger predators, so they are killed slowly from within by their own, radioactive blood.
To quote again:
"it would then emit the radiation whenever an atom decays - getting whatever happens to be local at that point."
Local at that point is somewhere in the animal, with a bit of bad luck in the bone marrow or the equivalent organ sharks use for creating red blood cells, which is an environment with lots of quickly dividing cells.
The paper suggests muon radiation affecting animals in shallow (or surface) waters. A muon carries a hell of a punch so it can penetrate into the water and then cause damage to cells. The bigger the animal, the bigger the risk of developing something nasty.
This might explain an oddity of the Pliocene-Pleistocene megafauna extinction; it doesn't appear to involve a collapse of the bottom of the food chain - microfauna and flora don't seem to go to the wall as they did say in the KPg event; instead this extinction disproportionately affects large animals.
There was a paper published in 2002 that pointed out a group of OB supergiants would have passed relatively close to the Earth. Had one of those exploded at the right/wrong time it would have had an effect on the Earth.
Narciso Benítez, Jesús Maíz-Apellániz, and Matilde Canelles et al. (2002). "Evidence for Nearby Supernova Explosions".
I thought water was supposed to be an excellent protector against radiation?
I had to look it up as I couldn't remember, but "secondary muons generated by cosmic rays hitting the atmosphere can penetrate to the Earth's surface, and even into deep mines." For the length of time the Earth was purportedly showered with an intensified amount of this radiation, it would have been difficult and unlikely for large animals to avoid exposure.
So if you have a 2% chance of dying from cancer it would rise to a whopping 3%? On no!
That's 50% increase for something the size of a human. Since you only need to get cancer in one cell, and it then spreads, if something is irradiating you, the larger cross-section you have, the higher the chance of one cell getting hit. Megaladons were quite large (60 feet, 130 linguine, or 2 double-decker buses) so would have been affected much much more than a human. Larger animals also tend to breed slower than smaller ones. There would have been a cut-off point in size, where that 2% would become high enough to kill things off faster than they breed, which would cause extinction.
So another possible one-off event to add to the tally on whether intelligent life is common or not.
Our universe itself keeps on expanding and expanding,
In all of the directions it can whiz;
As fast as it can go, at the speed of light, you know,
Twelve million miles a minute and that's the fastest speed there is.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth;
And pray that there's intelligent life somewhere out in space,
'Cause there's bugger all down here on Earth!
Such scenario shouldn't have caused a very lethal extinction outside water? Also, shouldn't we spot some SN remains nearby, especially if it was a whole chain? Maybe a small black hole without gas around can be hard to identify (unless it perturbs something around), but a neutron star could have some chances to be identified as a pulsar, and a close pulsar with its beams directed towards us could not be nice as well.
Also, OB stars to be exploded only 2.6M years ago should have formed far later than Sun. Larger stars don't usually form earlier, when there's more mass available? Or something else started the formation of a group of star later (another SN impact wave?)
There's an apparent terrestrial megafauna extinction at around the same time as in the oceans. However, terrestrial fossils are much rarer than those in the oceans and they tend to be less well constrained in terms of date in part because suitable microfauna and microfloral fossils aren't as common on land.
The Pliocene-Pleistocene is also problematic because the climate was turning towards a glacial epoch and a lot of the uppermost Pliocene terrestrial deposits were either eroded or extensively reworked by advancing ice sheets. There's still some dispute over the exact boundary between the two in many parts of the world as there is no clear boundary.
Anyone know the lifetime of a visible neutron star? I rather suspect it will have cooled below the visible spectrum long ago. And of course, we don't know where to look.
As for the formation date - yep, an OB star has a life measured in mere tens of millions of years, so it couldn't have formed at the same time as the Sun. However, it's important to remember that whilst all stars orbit the centre of the Milky Way, they do not follow parallel orbits and are constantly rising and falling through the central plane of the galaxy. Our neighbourhood supernovae could be a long way away by now.
One proposal is that the killer might lie in a group of stars called the Scorpius–Centaurus Association which is between 380 and 470 light years away and is dominated by large, hot stars. Though other candidates are probably out there.
Anyone know the lifetime of a visible neutron star? I rather suspect it will have cooled below the visible spectrum long ago.
If they behave (thermally at least) like a white dwarf, then they will be extremely hot and cool down very slowly, effectively being a stellar core only able to lose heat by radiation. It's more likely that they would be difficult to spot visually because of their extremely small diameter (~20km) rather than because of their lack of inherent brightness.
It's still one I enjoy re-reading because of the way they wove the story. They tied physical evidence on earth to other evidence of a supernova causing an extinction-level event.
As more than one scientist has enquired over the years: "Where is everybody?"
Although the supposed equation that purports to tell you the odds of intelligent life in the universe is horseshit*¹, it remains true that even our own little galaxy is enormous, with hundreds of billions of stars that have been around for billions of years: you do have to wonder why we haven't picked up the slightest sign of EM from distant civilisations. Some would surely have been around during the last few millions of years, and at least a few stray seconds of "Tentacles of Doom", a primetime favourite among the Bogglegrophh Slimers of ε-Eridani-IV/2, should have been picked up?
The more we've learned about mass extinctions and their causes, the more a plausible explanation heaves into view: the truth is, the universe at large is incredibly hostile to life and it is astoundingly unlikely that we have survived this long.
Events like the Siberian Trappes outpouring probably killed a large majority of all life on Earth (Permian extinction). Similar things have happened several times. Impactors like the Chicxulub impactor 65Mya, possibly associated with more eruptions, years ago wiped out all big land animals on earth (K-T boundary). A big fast comet sweeping from the direction of the sun could give us only weeks to prepare for civilisation to end. We may be committing species suicide with pollution and warming anyway. A local nova or more distant supernova could sterilise the planet. A wandering black hole or neutron start could wreak havoc. A very distant gamma-ray burster could by chance point right at us. A big CME from our own sun, aimed at us, could cause such upheavals as to bring the world to nuclear armageddon. Even if you exclude all the ways we could kill oursleves, the universe and even our own galaxy is full of dangers. We don't know all of them yet, nor their frequency and likely proximity.
It seems increasingly possible that life almost always gets snuffed out or knocked back, that the evolution of sentience is incredibly rare, and that species achieving it become abe to indulge their greed so well that they kill themselves off soon afterwards, before they can venture far from home.
Perhaps we should look for sentient civilisations not in crowded galactic space, but in very sparesely populated volumes ...?
*¹ You know the kind of thing: "If one in a thousand stars has planets in the Goldilocks Zone; and one in a thousand planets develops life; and one in a thousand evolves sentient tool users ..."—then supposedly there are X,000 intelligent species out there. It's crap because the single critical assumption has no answer. We have absolutely no idea, using our sample of one (Earth) whether, even on a Goldilocks planet, the probability of life is 1:10 or 1:10^40. We know it's possible; but no one knows how likely it is. So the entire "equation" breaks down.( And yes, you may say, "But surely over, say, 100m years, the chances get better?" True, but it makes no difference at long odds. First, 100m years is no time at all for a 1:1^40 chance not to happen. Second, that's 100m years in which a local nova can clean the slate, again.
"Although the supposed equation that purports to tell you the odds of intelligent life in the universe is horseshit*¹"
You mean the Drake equation - https://www.space.com/25219-drake-equation.html - which in almost 60 years no one's come up with something better?
The equation isn't horseshit, but our ability to populate it with accurate numbers is. So the more that scientists learn about planets etc and are able to improve our knowledge of each part of the equation, the more accurate the result it returns will be. In the case of natural disasters, that's where fl, fi, fc and L come into play.
"Although the supposed equation that purports to tell you the odds of intelligent life in the universe is horseshit ..."
You are dismissing Drake's equation as horseshit on the basis that we don't know all of the values to substitute into it. I thinks that's acknowledged by just about everyone who discusses it but that doesn't invalidate the equation nor its use in speculating on "what if" possibilities.
In fact, the equation includes a factor for how long intelligent life can be expected to survive on average and if that figure is low - as you suggest - then it would lead to a small number of other civilisations existing at the same time as us.
A bear of little brain asks: where is this 'rain of Iron-60' coming from?
Is this ejecta from the supernova, travelling at something close to the speed of light, so that it gets to the Earth only a few thousand years after the radiation - close enough that the two appear to be more or less the same in the fossil record?
Or is it a reaction that takes place on Earth - the supernova radiation striking an atom (regular Iron presumably?) and converting it to Iron-60 on Earth?
A cursory Google doesn't seem to offer an explanation and my knowledge of chemistry is so little that I'm not sure what else to search under.
Or is it a reaction that takes place on Earth - the supernova radiation striking an atom (regular Iron presumably?) and converting it to Iron-60 on Earth?
I'd tend to think not. If you've got Iron-58 (the heaviest stable isotope, but don't ask me how common it is) on Earth, you'd need to slam two neutrons into it to form Iron-60. What would be the energy required such that a neutron would become part of the atom rather than split it, and what would be the odds that two such neutrons struck the same atom (rather than none, only one, or three or more, or one followed by a fast neutron)? If there is a bath of radiation capable of generating such neutrons when it strikes the atmosphere, how intense must it be and how long must it last to free or create enough neutrons of the right energy to give the results we see?
Its easier to make Iron-60 from something heavier like Nickel or Cobalt - you hit it with radiation and it creates an isotope than then decays to Iron-60 - not sure of the route yet!
Not a NukeE but as far as I know hitting anything with radiation won't do a damned thing about/to its atomic number. For that you need something heavy like a Neutron
You hit it with something and it turns a proton into a neutron reducing is atomic number by one, possibly making it unstable so it decays into something else.
Having said that I cruised the periodic table and couldn't find anything that seems to decay to Fe60 so perhaps it needs to be fused and blasted across the universe, possibly arriving
And I've just found a paper that says Fe60 can only be made in a supernova so it must be fired at us at near light speed. I wonder if there are any deposits that would allow us to estimate how near the nova was.
Lol an exploding star lightyears away caused things on our planet to change?
Everyone knows it was the dinosaurs use of internal combustion engines and their over reliance on meat causing them to fart too much.
The world NEVER changes unless it is caused by the dominant lifeforms on this planet. I think they should look for evidence of dinosaur wind turbines before declaring that some magic rays from spaaaace affected our planet.
Marine animals like the megalodon ... suddenly disappeared during the late Pliocene. Around the same time, scientists from the University of Kansas and the Federal University of São Carlos, noticed a peak in the iron-60 isotope in ancient seabeds.
I have it on good authority that the University of Kansas was founded in 1865. Thus there cannot have been any scientists from the University of Kansas during the late Pliocene. QED.
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