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The Amazing Trajectories of Life-Bearing Meteorites from Earth
The asteroid that killed the dinosaurs must have ejected billions of tons of life-bearing rock into space. Now physicists have calculated what must have happened to it.
About 65 million years ago, the Earth was struck by an asteroid some 10 km in diameter with a mass of well over a trillion tons. We now know the immediate impact of this event—megatsunamis, global wildfires ignited by giant clouds of superheated ash, and, of course, the mass extinction of land-based life on Earth.
But in recent years, astrobiologists have begun to study a less well known consequence: the ejection of billions of tons of life-bearing rocks and water into space. By some estimates, the impact could have ejected as much mass as the asteroid itself.
The question that fascinates them is what happened to all this stuff.
Today, we get an answer from Tetsuya Hara and buddies at Kyoto Sangyo University in Japan. These guys say a surprisingly large amount of Earth could have ended up not just on the Moon and Mars, as might be expected, but much further afield.
In particular, they calculate how much would have ended up in other places that seem compatible for life: the Jovian moon Europa, the Saturnian moon Enceladus, and Earth-like exoplanets orbiting other stars.
Their results contain a number of surprises. First, they calculate that almost as much ejecta would have ended up on Europa as on the Moon: around 10^8 individual Earth rocks in some scenarios. That's because the huge gravitational field around Jupiter acts as a sink for rocks, which then get swept up by the Jovian moons as they orbit.
But perhaps most surprising is the amount that makes its way across interstellar space. Last year, we looked at calculations suggesting that more Earth ejecta must end up in interstellar space than all the other planets combined.
Hara and co go further and estimate how much ought to have made its way to Gliese 581, a red dwarf some 20 light years from here that is thought to have a super-Earth orbiting at the edge of the habitable zone.
They say about a thousand Earth-rocks from this event would have made the trip, taking about a million years to reach their destination.
Of course, nobody knows if microbes can survive that kind of journey or even the shorter trips to Europa and Enceladus. But Hara and buddies say that if microbes can survive that kind of journey, they ought to flourish on a super-Earth in the habitable zone.
That raises another interesting question: how quickly could life-bearing ejecta from Earth (or anywhere else) seed the entire galaxy?
Hara and co calculate that it would take some 10^12 years for ejecta to spread through a volume of space the size of the Milky Way. But since our galaxy is only 10^10 years old, a single ejection event could not have done the trick.
However, they say that if life evolved at 25 different sites in the galaxy 10^10 years ago, then the combined ejecta from these places would now fill the Milky Way.
There's an interesting corollary to this. If this scenario has indeed taken place, Hara and co say: "then the probability is almost one that our solar system is visited by the microorganisms that originated in extra solar system."
Entertaining stuff!
Ref: arxiv.org/abs/1204.1719: Transfer of Life-Bearing Meteorites from Earth to Other Planets
Is a such thing really possible ?
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2 things bug me:
while we have extremly hard to launch rockets and spacecraft into space... can some rocks from the impact really fly in the air with enough velocity and enough energy to last long enough to mock the terrestrial gravity ?
and 2nd : i know it s pretty accepted the theory about a big asteroid hit the earth and made disappeared life and dinosaurs.... but how they can be so sure about its diameters and its mass ? and where it did hit the earth ? they have proof about where it did it ?
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To summarize. We do know where the asteroid hit and we can judge it's TNT equivalent. Also, not all life was wiped out. A small mammal survived; perhaps it was underground and it eventually evolved over 250,000,000 years to us homo sapiens. Lots of saps and a few homos apparently. |
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double post?
edited by me
john3760
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65,000,000 years ago ?
We now know that dinosaurs weren't wiped out during this mass extinction event.
All life over a certain size was wiped out,( apart from a few species such as crocodilians
which can survive without food for extended periods ,or on rotten carcasses ).
It was also a mass extinction event for plant species as well.
The animal species which survived the impact,and ensuing years of hardship,were all small
and probably could burrow or hide underground when the firestorm engulfed the earth(mammals
/ reptiles/ insects etc), or live in water ( fish/ reptiles /amphibians etc).
Some species may have survived purely because their eggs were buried,and hatched out into
a post apocalyptic world.
Small dinosaurs survived as well ,we know their descendants today as birds.
john3760
p.s @ Michael . The Yukatan crater has been dated to 65,000,000 years ago.
In addition to that, there is a worldwide layer of deposited ejecta
called the KT boundary layer.This also dates to the same time,
plus the deposit is thicker,the closer you get to the crater.This is
good way of tying these two things together.
You can calculate the mass of ejected material, by measuring
the thickness of this layer around the planet,then the force that
would be needed to eject this amount of material.
You can then calculate the size of the object which must have hit
the earth to produce this force.
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guess again. the element is iridium.
http://en.wikipedia.org/wiki/Iridium
K–T boundary presence
A cliff with pronounced layered structure: yellow, gray, white, gray. A red arrow points between the yellow and gray layers.
The red arrow points to the K–T boundary.
Main article: Cretaceous–Tertiary extinction event
The K–T boundary of 65 million years ago, marking the temporal border between the Cretaceous and Tertiary periods of geological time, was identified by a thin stratum of iridium-rich clay.[41] A team led by Luis Alvarez proposed in 1980 an extraterrestrial origin for this iridium, attributing it to an asteroid or comet impact.[41] Their theory, known as the Alvarez hypothesis, is now widely accepted to explain the demise of the dinosaurs. A large buried impact crater structure with an estimated age of about 65 million years was later identified under what is now the Yucatán Peninsula (the Chicxulub crater).[42][43] Dewey M. McLean and others argue that the iridium may have been of volcanic origin instead, as the Earth's core is rich in iridium, and active volcanoes such as Piton de la Fournaise, in the island of Réunion, are still releasing iridium.[44][45]
Iridium is incredibly rare on earth and its origins appear to be almost 100% from asteroids and meteors.
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The implications of this finding seem remarkable. Assume that very basic forms of life can survive for long periods in space. It is an idea that has been discussed before and found at least plausible. If it is so, it appears that large tracts of interstellar space have been seeded with life, not only from Earth, but from extrasolar planets that have experienced impacts similar to the one at out K-T boundary. There has been the tendency to think of Earth, or at least our solar system, as biologically isolated from the rest of the universe. It begins to appear that a good deal of back and forth mixing; seeding, reseeding and transplanting of life might occur between many different stellar systems. |
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Unfortunately the rocket failed or we might have some real idea behind panspermia.
http://www.planetary.org/programs/projects/life/
Hopefully there will be another launch opportunity for this important research.
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2 things bug me:
while we have extremly hard to launch rockets and spacecraft into space... can some rocks from the impact really fly in the air with enough velocity and enough energy to last long enough to mock the terrestrial gravity ?
Yes, a good deal of material from such an impact could enter space provided it didn't vaporize in the atmosphere first. We've used a nuclear detonation to launch an object at several times escape velocity, and the K-T impact event was far more powerful than any manmade device. I think the more important question is, would any life actually survive within these chunks of superheated and molten rock?
and 2nd : i know it s pretty accepted the theory about a big asteroid hit the earth and made disappeared life and dinosaurs.... but how they can be so sure about its diameters and its mass ? and where it did hit the earth ? they have proof about where it did it ?
The impact crater from the event has been identified with a fair degree of confidence as the Chicxulub Impact Crater off the Yucatan Peninsula in Mexico. The age of the crater fits the timeframe for the event, and its size coupled with the resulting worldwide layer of iridium fallout give a good estimate as to the asteroid's size and mass.
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While an impact of that magnitude will certainly cause debris to be ejected out into space, space is so vast that the odds of one of these ejected rocks getting to another star system and impacting on an earth-like planet there is quite astronomical. That's if the debris even escapes the Sun's grasp, which it probably won't. |
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i dunno i still hard to believe :P it needs to be really big, a really big meteorite but in same time, more bigger it is , and more it could disrupt the planet earth itself.
thx for the infos about the Chicxulub Crater, going to read on it,
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The escape velocity from the Earth's surface is around 11 km/s, and the solar escape velocity (at the distance of the earth from the sun) is about 42 km/s. Meanwile, asteroids and comets can zip along at 50 or more km/s. If it hits at 50 km/s, then it is not so hard to imagine it could kick bits of rock out at 42 km/s.
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then it is not so hard to imagine it could kick bits of rock out at 42 km/s.
At this speed then how much of this ejected material would burn up as it
passes back up and out through our atmosphere.
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The Kite Fliers
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Kite fliers: An imaginary club of solo members, those who don't yet
belong to a formal team so "fly their own kites" - as the saying goes. |
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then it is not so hard to imagine it could kick bits of rock out at 42 km/s.
At this speed then how much of this ejected material would burn up as it
passes back up and out through our atmosphere.
Rocks come into the atmosphere everyday and get a little singed but make it to the surface, going the other way wouldn't be much different.
As for life surviving the trip: there are bacteria that thrive in deep-sea vents, in volcanoes, and other places that are fairly extreme. Life tends to be pretty darn tough.
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As for life surviving the trip: there are bacteria that thrive in deep-sea vents, in volcanoes, and other places that are fairly extreme. Life tends to be pretty darn tough.
Surface bacteria would most probably get annihilated by the radiation out in
space. Inner rock bacteria could most probably survive this but still how
long can they live, time wise, protected inside a rock.
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The Kite Fliers
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Kite fliers: An imaginary club of solo members, those who don't yet
belong to a formal team so "fly their own kites" - as the saying goes. |
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As for life surviving the trip: there are bacteria that thrive in deep-sea vents, in volcanoes, and other places that are fairly extreme. Life tends to be pretty darn tough.
Surface bacteria would most probably get annihilated by the radiation out in
space. Inner rock bacteria could most probably survive this but still how
long can they live, time wise, protected inside a rock.
lets not forget that there is a bacteria that can grow and prefers to grow in the water of Nuclear reactors. So radiation may not be a limitation
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End terrorism by building a school
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Gary Charpentier
