Re: SETI ET lefthanded or righthanded?


Chris Boyce (cb@ndirect.co.uk)
Fri, 11 Jun 1999 07:49:36 +0100


John & all, Re: 1) The complexity of DNA suggests it evolved from another form, that it is the end result of a series of organochemical evolutionary steps, likewise RNA. Accordingly, if we find nucleic acids closely similar to these in the Solar System there may be a case to be made for some kind of limited 'panspermia'. By this I mean that life - or at least the nucleic acids - may have evolved in one place so early in the history of the System that the frequency of impacts scattered it amongst the planets and other bodies. Re: 1) I would anticipate a predominantly right-handed biology, since we are the evidence for it. If there is a proportional relationship between right and left handed biologies, then, unless it is exactly equal, our own experience indicates that the probability is right-handedness predominates. Should there be left-handed biologies, the probability is still that in our section of space there are more right than left. Anyway a universally right handed biological cosmos would not be all that surprising as the universe is replete with broken symmetries. Best regards Chris Boyce ET-Presence - http://www.et-presence.ndirect.co.uk/ HOGMANAYCON - http://www.ndirect.co.uk/~cb/conpage.htm ----- Original Message ----- From: John Bush <jebush@ridgecrest.ca.us> To: <seti@sni.net> Sent: 09 June 1999 23:46 Subject: SETI ET lefthanded or righthanded? > Two questions, assuming ET life is based on carbon: > > 1) We know that except for very minor differences, the genetic code is the > same for all species on earth, from the simplest bacterium to the most > complex radio astronomer. A most intriguing question in my view is: "is the > genetic code universal?" If we find life-as-we-know-it (carbon-based) on > Mars, Europa, a nearby star system, another galaxy, will we find it to have > the same genetic code, the same 20 amino acids as earth based life? What are > the implications if we all use the same code? > > 2) Life on earth is based on left-handed amino acids, right-handed sugars > (e.g. dextrose). There's some evidence of preferred -handedness or > chiriality from some of the carbon compounds found in certain meteorites > (carboniferous chrondites?) but I'm not sure how compelling it is. Anybody > know? Anyway whether the answer to 1) is yes or no, it's still probable that > any carbon-based life-as-we-know-it will involve the manufacture of sugars > for the basic energetics of life. So the question is will the sugar be > right-handed? What are the implications if half the worlds are left-handed > and half are right-handed? > > Too bad there aren't more biologists interested in SETI - perhaps they would > have more insight into these matters than the astronomers. > > __jeb >



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