Did we already colonized the Milky Way ?


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Profile Michel448a
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Message 1217353 - Posted: 12 Apr 2012, 18:35:19 UTC

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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Message 1217362 - Posted: 12 Apr 2012, 19:08:58 UTC

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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Message 1217405 - Posted: 12 Apr 2012, 21:28:45 UTC
Last modified: 12 Apr 2012, 21:47:08 UTC

This reminds me of the movie "Deep Impact".

Although maybe another story, we are not supposed to see the material (made of dust) which exists between stars and possibly not only between stars but also between galaxies and maybe even clusters of galaxies.

When the meteor depicted in "Deep Impact" hit the Earth, it hit the ocean, but at a shallow angle, like someone standing on a cliff in front of some water and throwing a stone straight forward in a horizontal direction.

After a few moments the motion of this stone will be affected by several factors.

First air resistance, next gravity from Earth.

But gravity is readily thought of as supposedly speeding up the motion of falling objects.

The speed of the falling stone in relationship with the ground will increase, not only because of the speed of the object itself, but because of the pull of gravity.

When it comes to big meteorites and asteroids, these time frames are so short that the influence of gravity from Earth is possibly insignificant. Still the angle of direction is an important factor. If an asteroid hits open water from straight above in relationship with its impact point, it will create waves in all directions.

A similar hit from a meteor as depicted in "Deep Impact" will push up water in the same direction as the one which the meteor was having when entering Earth's atmosphere.

The asteroid which made the dinosaurs extinct is thought to have occurred in shallow waters, at an angle, near Yucatan, Mexico, in the same way as depicted in "Deep Impact".

The resulting wave from this impact pushed inland and probably destroyed all life in continental U.S.A or maybe even North America as a whole. The shockwave and following cloud of ash from the impact went around the Earth several or many times, air was sucked up into the atmosphere with the result of killing off all high level organism on land as a result.

Most of the life in the oceans also vanished as a result of this event.

As a result of this impact, life had to start up again from scratch both in water as well as on dry land.

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Message 1217451 - Posted: 13 Apr 2012, 0:03:15 UTC
Last modified: 13 Apr 2012, 0:03:30 UTC

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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Message 1217470 - Posted: 13 Apr 2012, 1:01:46 UTC
Last modified: 13 Apr 2012, 1:18:48 UTC

double post?
edited by me

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Message 1217474 - Posted: 13 Apr 2012, 1:17:30 UTC
Last modified: 13 Apr 2012, 1:20:09 UTC

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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Message 1217489 - Posted: 13 Apr 2012, 2:11:51 UTC
Last modified: 13 Apr 2012, 2:26:32 UTC

The special element which is abundant in meteorites and asteroides is Nickel (or Nikkel in my own language).

Atomic number is 28. Checking out with http://en.wikipedia.org/wiki/Nickel gives me this correct syntax for this element.

It is now late night here and I am relaxing right now after a somewhat bad day.

So, therefore, I also could have said "probably" rather than "possibly" in my previous posting.

Anyway, when digging (or making excavations) into the soil, this element is being found as making up a white line of some thickness (a couple of centimeters/decimeters).

This tells us how much of this periodic element which was deposited across the Earth as a result of this impact
(and other impacts in the past).

Similarly, another periodic element which is NOT found in meteorites or asteroides is Cadmium, Atomic number 48.

Check out http://en.wikipedia.org/wiki/Cadmium for this periodic element.

My best guess is that this element is poisonous to humans.

But to be honest, why not stick to the question of the original poster (OP)?

Organic molecules, if possibly brought through space by means of "meandering" metorites are indeed acid molecules.

Why is it not so when it comes to bases as well or instead of acids?

Does there exist a similar base alternative for DNA which is itself an acid and the basis for both life and possibly intelligent life (by means of the ability of thinking as well as dreaming)?

Also trees are having a very complex organic molecule (even bigger than DNA) in its organic structure. Plants are green in color because of Magnesium rather than Iron in its molecule core.

Sugar is an acid. What about the salt which you may put on your breakfast egg?

Salt is NaCl (Natrium/Chloride)or KCl (Kalium/Chloride). Calcium (or Ca) you get inside your body when you drink a glass of milk in the morning.

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Message 1217622 - Posted: 13 Apr 2012, 12:11:31 UTC - in response to Message 1217489.
Last modified: 13 Apr 2012, 12:12:33 UTC

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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Message 1217641 - Posted: 13 Apr 2012, 14:17:32 UTC

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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Message 1217770 - Posted: 13 Apr 2012, 19:40:51 UTC

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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Message 1217793 - Posted: 13 Apr 2012, 20:29:05 UTC - in response to Message 1217622.
Last modified: 13 Apr 2012, 20:36:29 UTC

Yes, skildude. Apparently you corrected my mistake here. I don't think it happens too often, though.

As long as we are able to both think as well as dream and also learn something, we trust our brain cells for this capability.

Then it is time to consult the doctor or at least a medical book which may be dealing with the relevant subject.

The neurological functions of a human brain, which except for the possible ear disturbances you may be having from time to time due to possible illness is created by means of electricity.

Also these functions may be creating waves on their own.

Do we ever think of electricity as consisting of waves?

If someone had the capability of traveling between the stars, one way of surviving such a long journey (except for the constant ageing which may still be occurring) is living in hibernation.

Which really is a little more than just a deep sleep. I guess you will not be able to dream very much in such a state.

Remember that you still may be traveling at nearly the speed of light. You are not supposed to become very much older during such a long journey.

In order to get back up again when you finally arrive at your final destination, you may need to get some kind of a wake-up call.

Also you will have to go the same way back again, when you are returning home.

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Message 1217812 - Posted: 13 Apr 2012, 21:22:51 UTC - in response to Message 1217362.

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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Message 1218255 - Posted: 14 Apr 2012, 15:00:50 UTC
Last modified: 14 Apr 2012, 15:07:07 UTC

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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Message 1218431 - Posted: 14 Apr 2012, 21:55:48 UTC

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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Message 1218448 - Posted: 14 Apr 2012, 22:45:45 UTC
Last modified: 14 Apr 2012, 22:46:11 UTC

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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Message 1220323 - Posted: 19 Apr 2012, 15:40:11 UTC - in response to Message 1218448.

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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Message 1220503 - Posted: 20 Apr 2012, 4:11:58 UTC - in response to Message 1220323.

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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Message 1221281 - Posted: 21 Apr 2012, 17:54:14 UTC - in response to Message 1220503.
Last modified: 21 Apr 2012, 17:59:02 UTC

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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Message 1221374 - Posted: 21 Apr 2012, 20:55:41 UTC - in response to Message 1221281.

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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