Aug 27, 2015 11:39 PM
Life May Have Spread Through the Galaxy Like a Plague
http://www.smithsonianmag.com/science-na...180956425/
EXCERPT: [...] Panspermia is the theory that the seeds of life somehow came to our planet from another world. The idea is controversial at best—most biologists would tell you that it just pushes the problem back a step, because we still wouldn't know what sparked life in the first place. And so far, there’s little reason to think life on other planets should be anything like what we see on Earth.
Now Henry Lin and Abraham Loeb of Harvard University say that if we do see evidence of alien life, the distribution of inhabited planets would be a “smoking gun” for panspermia. According to their model, if life arises on a few planets and spreads through space to others, inhabited planets ought to form a clumpy pattern around the galaxy, with voids between roughly spherical regions. This bubble pattern appears no matter how the distribution happens, whether its aliens traveling by spaceship or comets carrying life’s building blocks....
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Interstellar seeds could create oases of life
http://www.eurekalert.org/pub_releases/2...082715.php
RELEASE: We only have one example of a planet with life: Earth. But within the next generation, it should become possible to detect signs of life on planets orbiting distant stars. If we find alien life, new questions will arise. For example, did that life arise spontaneously? Or could it have spread from elsewhere? If life crossed the vast gulf of interstellar space long ago, how would we tell?
New research by Harvard astrophysicists shows that if life can travel between the stars (a process called panspermia), it would spread in a characteristic pattern that we could potentially identify.
"In our theory clusters of life form, grow, and overlap like bubbles in a pot of boiling water," says lead author Henry Lin of the Harvard-Smithsonian Center for Astrophysics (CfA).
There are two basic ways for life to spread beyond its host star. The first would be via natural processes such as gravitational slingshotting of asteroids or comets. The second would be for intelligent life to deliberately travel outward. The paper does not deal with how panspermia occurs. It simply asks: if it does occur, could we detect it? In principle, the answer is yes.
The model assumes that seeds from one living planet spread outward in all directions. If a seed reaches a habitable planet orbiting a neighboring star, it can take root. Over time, the result of this process would be a series of life-bearing oases dotting the galactic landscape.
"Life could spread from host star to host star in a pattern similar to the outbreak of an epidemic. In a sense, the Milky Way galaxy would become infected with pockets of life," explains CfA co-author Avi Loeb.
If we detect signs of life in the atmospheres of alien worlds, the next step will be to look for a pattern. For example, in an ideal case where the Earth is on the edge of a "bubble" of life, all the nearby life-hosting worlds we find will be in one half of the sky, while the other half will be barren.
Lin and Loeb caution that a pattern will only be discernible if life spreads somewhat rapidly. Since stars in the Milky Way drift relative to each other, stars that are neighbors now won't be neighbors in a few million years. In other words, stellar drift would smear out the bubbles.
http://www.smithsonianmag.com/science-na...180956425/
EXCERPT: [...] Panspermia is the theory that the seeds of life somehow came to our planet from another world. The idea is controversial at best—most biologists would tell you that it just pushes the problem back a step, because we still wouldn't know what sparked life in the first place. And so far, there’s little reason to think life on other planets should be anything like what we see on Earth.
Now Henry Lin and Abraham Loeb of Harvard University say that if we do see evidence of alien life, the distribution of inhabited planets would be a “smoking gun” for panspermia. According to their model, if life arises on a few planets and spreads through space to others, inhabited planets ought to form a clumpy pattern around the galaxy, with voids between roughly spherical regions. This bubble pattern appears no matter how the distribution happens, whether its aliens traveling by spaceship or comets carrying life’s building blocks....
- - - - - - - - -
Interstellar seeds could create oases of life
http://www.eurekalert.org/pub_releases/2...082715.php
RELEASE: We only have one example of a planet with life: Earth. But within the next generation, it should become possible to detect signs of life on planets orbiting distant stars. If we find alien life, new questions will arise. For example, did that life arise spontaneously? Or could it have spread from elsewhere? If life crossed the vast gulf of interstellar space long ago, how would we tell?
New research by Harvard astrophysicists shows that if life can travel between the stars (a process called panspermia), it would spread in a characteristic pattern that we could potentially identify.
"In our theory clusters of life form, grow, and overlap like bubbles in a pot of boiling water," says lead author Henry Lin of the Harvard-Smithsonian Center for Astrophysics (CfA).
There are two basic ways for life to spread beyond its host star. The first would be via natural processes such as gravitational slingshotting of asteroids or comets. The second would be for intelligent life to deliberately travel outward. The paper does not deal with how panspermia occurs. It simply asks: if it does occur, could we detect it? In principle, the answer is yes.
The model assumes that seeds from one living planet spread outward in all directions. If a seed reaches a habitable planet orbiting a neighboring star, it can take root. Over time, the result of this process would be a series of life-bearing oases dotting the galactic landscape.
"Life could spread from host star to host star in a pattern similar to the outbreak of an epidemic. In a sense, the Milky Way galaxy would become infected with pockets of life," explains CfA co-author Avi Loeb.
If we detect signs of life in the atmospheres of alien worlds, the next step will be to look for a pattern. For example, in an ideal case where the Earth is on the edge of a "bubble" of life, all the nearby life-hosting worlds we find will be in one half of the sky, while the other half will be barren.
Lin and Loeb caution that a pattern will only be discernible if life spreads somewhat rapidly. Since stars in the Milky Way drift relative to each other, stars that are neighbors now won't be neighbors in a few million years. In other words, stellar drift would smear out the bubbles.
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