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Author Topic:   Extraterrestrial Origins Of Life on Earth
BeagleBob
Member (Idle past 5676 days)
Posts: 81
Joined: 11-21-2007


Message 4 of 21 (471141)
06-15-2008 4:43 AM
Reply to: Message 3 by Fosdick
06-14-2008 4:12 PM


Re: Biospheres and ET origins
I'd say that given the recent evidence on amino acids being formed in space, the chances that it was stardust that synthesized the amino acids that gave rise to life on earth is quite high.
This model would help solve the problem of chirality very elegantly.

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 Message 3 by Fosdick, posted 06-14-2008 4:12 PM Fosdick has not replied

Replies to this message:
 Message 5 by Dr Jack, posted 06-15-2008 7:24 AM BeagleBob has replied
 Message 8 by Straggler, posted 06-17-2008 9:08 AM BeagleBob has not replied

  
BeagleBob
Member (Idle past 5676 days)
Posts: 81
Joined: 11-21-2007


Message 10 of 21 (471532)
06-17-2008 10:34 AM
Reply to: Message 5 by Dr Jack
06-15-2008 7:24 AM


Re: Biospheres and ET origins
quote:
The trouble is that amino acids don't often survive impact. When Bada et al investigated this by studying the Tunguska impact site for alpha-amino-isobutyric acid - which is common in interstellar space but extremely rare on earth - they didn't find any. (Here, page 12 - couldn't find a link to the research itself, sorry).
Some amino acids created in space probably do reach the Earth but it is extremely unlikely that they ever did so in anywhere near the concentrations that would be necessary to explain the origin of life.
I was referring to interstellar dust, not to asteroids.

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 Message 5 by Dr Jack, posted 06-15-2008 7:24 AM Dr Jack has replied

Replies to this message:
 Message 13 by Dr Jack, posted 06-17-2008 5:30 PM BeagleBob has replied

  
BeagleBob
Member (Idle past 5676 days)
Posts: 81
Joined: 11-21-2007


Message 12 of 21 (471557)
06-17-2008 12:34 PM
Reply to: Message 11 by Fosdick
06-17-2008 12:14 PM


Re: Biospheres and ET origins
quote:
Chirality suggests to me a single origin of life, rather than a multi-regional outbreak. But it suggests nothing about where that single origin occurred. If it happened extra-terrestrially and migrated to Earth, then we are caught by Mr Jack's assertion that organic molecules with chirality couldn't survive a panspermatic impact.
On the other hand, a rare survival can't be ruled out, given what little we know about abiogenesis.
”HM
Life as we know it uses only left-handed amino acids. If you had a bunch of right-handed amino acids tossed into the mix it'd be much, much, much harder for proteins made from purely left-handed amino acids to arise. So a primordial earth couldn't have a collection of amino acids that was a decent mixture of left and right-handed amino acids.
Also, why in the world are people bringing up asteroid impacts? Not everything that falls to the earth are large, solid masses. The most likely explanation is an accretion of interstellar dust earlier in Earth's history, when planets were still mopping up remaining residues.

This message is a reply to:
 Message 11 by Fosdick, posted 06-17-2008 12:14 PM Fosdick has replied

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BeagleBob
Member (Idle past 5676 days)
Posts: 81
Joined: 11-21-2007


Message 18 of 21 (471731)
06-17-2008 8:54 PM
Reply to: Message 13 by Dr Jack
06-17-2008 5:30 PM


Re: Biospheres and ET origins
quote:
Interstellar dust does not fall in sufficient quantities to create a high enough concentration to acount for the origin of life.
Well certainly not 5 billion years after the formation of the planet.
I will of course admit that I'm not a cosmologist so I don't know the rates of dust accretion 4 billion years ago. However, the hypothesis is so very compelling given the fact that it would solve the problem of chirality.
Edited by BeagleBob, : No reason given.
Edited by BeagleBob, : Word substitution: "hypothesis."

This message is a reply to:
 Message 13 by Dr Jack, posted 06-17-2008 5:30 PM Dr Jack has replied

Replies to this message:
 Message 20 by Dr Jack, posted 06-18-2008 4:45 AM BeagleBob has replied

  
BeagleBob
Member (Idle past 5676 days)
Posts: 81
Joined: 11-21-2007


Message 21 of 21 (471834)
06-18-2008 4:09 PM
Reply to: Message 20 by Dr Jack
06-18-2008 4:45 AM


Re: Biospheres and ET origins
Well now that's fascinating. I hope you brought enough sources to share with the rest of the class.

This message is a reply to:
 Message 20 by Dr Jack, posted 06-18-2008 4:45 AM Dr Jack has not replied

  
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