Galactic Panspermia: Spreading Life from Star to Star:

[beecee]

https://phys.org/news/2018-10-milky-life-star.html

For almost two centuries, scientists have theorized that life may be distributed throughout the universe by meteoroids, asteroids, planetoids, and other astronomical objects. This theory, known as Panspermia, is based on the idea that microorganisms and the chemical precursors of life are able to survive being transported from one star system to the next.

Expanding on this theory, a team of researchers from the Harvard Smithsonian Center for Astrophysics (CfA) conducted a study that considered whether panspermia could be possible on a galactic scale. According to the model they created, they determined that the entire Milky Way (and even other galaxies) could be exchanging the components necessary for life.

The study, "Galactic Panspermia," recently appeared online and is being reviewed for publication by the Monthly Notices of the Royal Astronomical Society. The study was led by Idan Ginsburg, a visiting scholar at the CfA's Institute for Theory and Computation (ITC), and included Manasvi Lingam and Abraham Loeb – an ITC postdoctoral researcher and the director of the ITC and the Frank B. Baird Jr. Chair of Science at Harvard University, respectively.

As they indicate their study, most of the past research into panspermia has focused on whether life could had been distributed through the solar system or neighboring stars. More specifically, these studies addressed the possibility that life could have been transferred between Mars and Earth (or other Solar bodies) via asteroids or meteorites. For the sake of their study, Ginsburg and his colleagues cast a wider net, looking at the Milky Way Galaxy and beyond.

Read more at: https://phys.org/news/2018-10-milky-life-star.html#jCp

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the paper:

https://arxiv.org/pdf/1810.04307.pdf

Galactic Panspermia:

ABSTRACT

We present an analytic model to estimate the total number of rocky or icy objects that could be captured by planetary systems within the Milky Way galaxy and result in panspermia should they harbor life. We estimate the capture rate of objects ejected from planetary systems over the entire phase space as well as time. Our final expression for the capture rate depends upon the velocity dispersion as well as the characteristic biological survival time and the size of the captured object. We further take into account the number of stars that an interstellar object traverses, as well as the scale height and length of the Milky Way’s disk. The likelihood of Galactic panspermia is strongly dependent upon the survival lifetime of the putative organisms as well as the velocity of the transporter. Velocities between 10 − 100 km s−1 result in the highest probabilities. However, given large enough survival lifetimes, even hypervelocity objects traveling at over 1000 km s−1 have a significant chance of capture, thereby increasing the likelihood of panspermia. Thus, we show that panspermia is not exclusively relegated to solar-system sized scales, and the entire Milky Way could potentially be exchanging biotic components across vast distances.

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Personally, as one who has always found Panspermia as an attractive reasonable proposition, I never had any thoughts of having it exclusively applying to Solar system size scales and saw Galactic Panspermia as a logical extension.

Edited October 15, 2018 by beecee

[StringJunky]

45 minutes ago, beecee said:

https://phys.org/news/2018-10-milky-life-star.html

For almost two centuries, scientists have theorized that life may be distributed throughout the universe by meteoroids, asteroids, planetoids, and other astronomical objects. This theory, known as Panspermia, is based on the idea that microorganisms and the chemical precursors of life are able to survive being transported from one star system to the next.

Expanding on this theory, a team of researchers from the Harvard Smithsonian Center for Astrophysics (CfA) conducted a study that considered whether panspermia could be possible on a galactic scale. According to the model they created, they determined that the entire Milky Way (and even other galaxies) could be exchanging the components necessary for life.

The study, "Galactic Panspermia," recently appeared online and is being reviewed for publication by the Monthly Notices of the Royal Astronomical Society. The study was led by Idan Ginsburg, a visiting scholar at the CfA's Institute for Theory and Computation (ITC), and included Manasvi Lingam and Abraham Loeb – an ITC postdoctoral researcher and the director of the ITC and the Frank B. Baird Jr. Chair of Science at Harvard University, respectively.

As they indicate their study, most of the past research into panspermia has focused on whether life could had been distributed through the solar system or neighboring stars. More specifically, these studies addressed the possibility that life could have been transferred between Mars and Earth (or other Solar bodies) via asteroids or meteorites. For the sake of their study, Ginsburg and his colleagues cast a wider net, looking at the Milky Way Galaxy and beyond.

Read more at: https://phys.org/news/2018-10-milky-life-star.html#jCp

<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

the paper:

https://arxiv.org/pdf/1810.04307.pdf

Galactic Panspermia:

ABSTRACT

We present an analytic model to estimate the total number of rocky or icy objects that could be captured by planetary systems within the Milky Way galaxy and result in panspermia should they harbor life. We estimate the capture rate of objects ejected from planetary systems over the entire phase space as well as time. Our final expression for the capture rate depends upon the velocity dispersion as well as the characteristic biological survival time and the size of the captured object. We further take into account the number of stars that an interstellar object traverses, as well as the scale height and length of the Milky Way’s disk. The likelihood of Galactic panspermia is strongly dependent upon the survival lifetime of the putative organisms as well as the velocity of the transporter. Velocities between 10 − 100 km s−1 result in the highest probabilities. However, given large enough survival lifetimes, even hypervelocity objects traveling at over 1000 km s−1 have a significant chance of capture, thereby increasing the likelihood of panspermia. Thus, we show that panspermia is not exclusively relegated to solar-system sized scales, and the entire Milky Way could potentially be exchanging biotic components across vast distances.

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

Personally, as one who has always found Panspermia as an attractive reasonable proposition, I never had any thoughts of having it exclusively applying to Solar system size scales and saw Galactic Panspermia as a logical extension.

Until the evidence suggests life couldn't happen on Earth, I'm not interested in panspermia.

[beecee]

9 minutes ago, StringJunky said:

Until the evidence suggests life couldn't happen on Earth, I'm not interested in panspermia.

That certainly would be ground breaking convincing evidence for Panspermia. 

 

[StringJunky]

7 minutes ago, beecee said:

That certainly would be ground breaking convincing evidence for Panspermia. 

 

Aye.

[Kevin Keogh]

On 10/15/2018 at 1:30 PM, StringJunky said:

Until the evidence suggests life couldn't happen on Earth, I'm not interested in panspermia.

Unfortunately, this bizarrely close-minded opinion is all too prevalent among scientists.

"Until the old way I learned this long before a lot of new evidence was discovered is totally disproven, I am simply not interested in weighing any new evidence objectively." 

Nobody has ever come close to creating life on earth. Nobody understands the the mechanisms that could create life on Earth. However, viable microbes could easily have arrived on Earth from elsewhere by known and well-demonstrated mechanisms.

I cannot fathom why so many scientists imagine the manner in which we know for certain things work on Earth (life always comes from previous life) somehow defies Occam's Razor when the concept is expanded to include extraterrestrial environments. Is this simply a pre-Copernican mentality that Earthly biochemical processes must be uniquely complex compared to those that exist in the rest of the universe?

I mean, if you found a colony of microbes on living on the Space Station or the Moon, would you simply assume that they spontaneously assembled themselves there until it was proven otherwise?

[StringJunky]

21 minutes ago, Kevin Keogh said:

Unfortunately, this bizarrely close-minded opinion is all too prevalent among scientists.

"Until the old way I learned this long before a lot of new evidence was discovered is totally disproven, I am simply not interested in weighing any new evidence objectively." 

Nobody has ever come close to creating life on earth. Nobody understands the the mechanisms that could create life on Earth. However, viable microbes could easily have arrived on Earth from elsewhere by known and well-demonstrated mechanisms.

I cannot fathom why so many scientists imagine the manner in which we know for certain things work on Earth (life always comes from previous life) somehow defies Occam's Razor when the concept is expanded to include extraterrestrial environments. Is this simply a pre-Copernican mentality that Earthly biochemical processes must be uniquely complex compared to those that exist in the rest of the universe?

I mean, if you found a colony of microbes on living on the Space Station or the Moon, would you simply assume that they spontaneously assembled themselves there until it was proven otherwise?

Start with the simplest scenario. Coming in from outside there are added difficulties. This does not presuppose that Earth is unique in its ability to start life. If life can start here, it can start anywhere that has the necessary conditions. It is an unnecessary complication to factor in how the building blocks landed on Earth when you haven't first eliminated that they were created here. Does that make sense?

Edited October 16, 2018 by StringJunky

[beecee]

21 minutes ago, Kevin Keogh said:

 Nobody has ever come close to creating life on earth. Nobody understands the the mechanisms that could create life on Earth. However, viable microbes could easily have arrived on Earth from elsewhere by known and well-demonstrated mechanisms.

I mean, if you found a colony of microbes on living on the Space Station or the Moon, would you simply assume that they spontaneously assembled themselves there until it was proven otherwise?

Obviously, scientifically speaking, Abiogenesis is the only answer as to how life arose in the universe...whether that was first on Earth and via Panspermia transported to other places,  whether somewhere else and transported to Earth, or whether and in my opinion far more likely, arose on more then one planet and and is still arising when conditions are suitable enough, with again Panspermia taking place. Take your pick.

[Kevin Keogh]

4 hours ago, StringJunky said:

Start with the simplest scenario. Coming in from outside there are added difficulties. This does not presuppose that Earth is unique in its ability to start life. If life can start here, it can start anywhere that has the necessary conditions. It is an unnecessary complication to factor in how the building blocks landed on Earth when you haven't first eliminated that they were created here. Does that make sense?

If microbial life started on Earth, it must have since spread and must continue to spread elsewhere in the solar system simply because it clearly has had both the time and the capability to do so. What could possibly sterilized all the trillions of Earthly microbe that have been launched outside the Earth's gravity well over the last 4+ billion years? I suppose other terrestrial bodies may have their own competitors, but microbial life on Earth is clearly well adapted to both space transport and subsurface survival elsewhere. Why would this be so were Earth the only habitat it had ever encountered? 

What makes life assembling itself from non-life in any specific location "simpler" than life arriving from another location? Don't we assume that all current life on Earth comes from previous life on Earth? So why stop this logical chain of reason at the Earth? Why assume the Earth is a closed system vis a vis the transfer of microbial life when it is clearly anything but? Once a self-replicating chemical system capable of interplanetary travel evolves, what stops it from colonizing nearby terrestrial bodies? Microbes don't need the sun, gravity, low radiation, or any environmental aspect unique to Earth. So why assume they are must be native to Earth when they obviously could have from elsewhere? Again, if we found a colony of microbes on the Moon, or the Space Station would it be "simpler" to assume that their first primordial ancestors evolved here or there?

[StringJunky]

6 hours ago, Kevin Keogh said:

What makes life assembling itself from non-life in any specific location "simpler" than life arriving from another location? 

Gravity  on a large body like Earth is not a trivial hurdle for life to escape, survive space and survive re-entry on another hospitable body, which would also likely be large. I'm not saying it's impossible but it's not a simpler solution than life starting on Earth. Executing Occam's Razor would tell us to start here, on Earth, for signs of the abiogenesis of life on Earth.

[DrP]

6 hours ago, Kevin Keogh said:

What makes life assembling itself from non-life in any specific location "simpler" than life arriving from another location?

5 minutes ago, StringJunky said:

Gravity  on a large body like Earth is not a trivial hurdle for life to escape, survive space and survive re-entry on another hospitable body, which would also likely be large. I'm not saying it's impossible but it's not a simpler solution than life starting on Earth. Executing Occam's Razor would tell us to start here, on Earth, for signs of the abiogenesis of life on Earth.

Also - if for arguments sake it did come from space....  then where did that come from?  You have the same problem of abiogenesis happening somewhere else. It clearly isn't any simpler.

 

[StringJunky]

3 minutes ago, DrP said:

Also - if for arguments sake it did come from space....  then where did that come from?  You have the same problem of abiogenesis happening somewhere else. It clearly isn't any simpler.

 

Exactly. One is just moving this puzzle to a more difficult starting place.

[DrP]

I read last year somewhere that regulated repeated assembly of certain polymeric units could have been influenced by the clays found on earth at the time it would have happened. The assembly can take place in the layers between the clay structures which can influence things like selective chirality and alignments. It wasn't 100% but was an interesting theory. Some post docs in my group a couple of decades ago were using similar catalysts (graphite not clay) to 'force' or favour certain alignments for their own polymerisations.  They found they could increase the yield of their desired chirality with the presence of graphite - they assumed or concluded that the polymerisation was taking place in between the plates/layers of graphite which was forcing a certain molecular orientation. Something similar could have happened in the layers in silicate clays to help get more regular repeatable arrangements and additions of the early building blocks for repeat units.   Still speculation as far as I am aware - but made a lot of sense.

[mistermack]

8 hours ago, Kevin Keogh said:

What could possibly sterilized all the trillions of Earthly microbe that have been launched outside the Earth's gravity well over the last 4+ billion years?

Cosmic rays. And Solar wind.

Also, while I can see how microbes can get lifted high up in the atmosphere by turbulence, I don't see how they can get any further. To avoid being pulled back down to Earth, the space station has to orbit at nearly 30,000 km per hour. Once a particle got away from any trace of atmosphere, it would accelerate downwards till it met other some gas. And size doesn't matter. It would fall as fast as the space station would fall, without it's orbital velocity. Even if it got as far away as the Moon, it would still be pulled straight back, without orbital speed. 

Then of course, if it somehow got away from Earth's gravity, it would still be orbiting the Sun. Solar storms and mass ejections regularly cause bursts of radiation that are even more damaging to life. A particle of living matter would probably be well and truly sterilised before it managed to float away from the Sun's gravity. Maybe the Solar Wind might help it on it's way a bit though?

And then of course, it would need energy to nip from the Solar System to the next star. I can't see where that's coming from.

So I can't see panspermia happening without intelligent action of some sort. The environment is too hostile and the distances are too great.