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Ian Goddard
2004-Mar-22, 04:08 AM
Here's an interesting theory from the New Scientist:

No Moon, no life on Earth, suggests theory

12:17 18 March 04

Without the Moon, there would have been no life on Earth.

Four billion years ago, when life began, the Moon orbited much closer to us than it does now, causing massive tides to ebb and flow every few hours. These tides caused dramatic fluctuations in salinity around coastlines which could have driven the evolution of early DNA-like biomolecules.

See: Full Report (http://www.newscientist.com/news/print.jsp?id=ns99994786)

Ian Goddard
2004-Mar-22, 04:34 AM
The contraposition of "If life, then Moon" is "If no Moon, then no life." Accordingly, Professor Lathe proposes that since Mars has no satellite sufficiently large to induce sufficient tides, Mars should have never had life. However, I think the evidence for the Martian meteorite ALH84001 having fossilized bacteria is very strong given recent findings (see here (http://www.ansto.gov.au/info/press/2004/p02.html) and here (http://badastronomy.com/phpBB/viewtopic.php?p=200638&sid=d8a8a17e0f0ad8f566dd05b 3aecdebac#200638)). But even if that's the case, Moon-induced tides may have been an important factor in the development of terrestrial life; although Lathe seems to insist that sufficient tidal forces are necessary for life.

Here's the abstract of the thread-leading hyopthesis:

Icarus, 168(1), March 2004, Pages 18-22

Fast tidal cycling and the origin of life

Abstract: Replicating prebiotic polymers are thought to predate the emergence of true life-forms. The initial mode of replication, a prerequisite for Darwinian selection, is unknown, but demands an explanation based on local physicochemistry. Dual consideration of the conditions of the early terrestrial surface, with the unusual physicochemical properties of nucleic acids like DNA, could explain the emergence of nucleic acids as key biomolecules. The early impact that produced the Moon, and fast terrestrial rotation, subjected coastal areas 3.9 Ga ago to rapid tidal flooding (dilution) and drying (concentration), with a likely periodicity in the range of 26 h, and could have provided a driving force for cyclic replication of early biomolecules. Such a mechanism applies only to molecules capable of association/polymerization at high salt concentration, and of dissociation at low salinity. Nucleic acids meet these criteria. It is suggested that tidal cycling, resembling the polymerase chain reaction (PCR) mechanism, could only replicate and amplify DNA-like polymers. This mechanism suggests constraints on the evolution of extra-terrestrial life.

Manchurian Taikonaut
2004-Mar-22, 05:31 AM
sounds like a good theory, but maybe there would be life expect it would be very simple and not grow well without a moon, some life but not like on Earth. Our moon is very important to the natural cycle of life on earth and its climate. Should we now use our furture SETI projects and radio telescope to search for signals from worlds with moons? This could be a better idea.

mike alexander
2004-Mar-22, 06:56 AM
What is the estimated salinity of the primordial oceans? Compared to now?

With such rapid tidal cycling, might not the effects be less likely? Two hours doesn't seem like very long for things to dry out.

I'm also playing with that 'tides several hundred kilometers inland' statement. Say a 4 hour tidal cycle (high-low high). Assume 'several hundred' is four hundred? So you have a tidal bore moving inland at 200 kilometers per hour, then back out again?

Sounds a bit abrasive.

Kaptain K
2004-Mar-22, 11:11 AM
So far, we have a sample size of one. Not very good for extrapolation.

Toutatis
2004-Mar-22, 11:50 AM
Without desire to assume the role of the proverbial 'wet blanket';

Re: Fossils discovered in Martian Meteorite ALH84001

Is it not possible - even *probable* - that said fossils owe to Martian contamination by terrestrial protozoa via similar Earth Ejecta???

I'm no statistician - still it seems a concept beyond credulity that organisms should have evolved in so parallel a fashion sans a 'connection'!!!

My $.02 FWIW :)
Respectfully

Dan Sarandon :-)

Swift
2004-Mar-22, 02:10 PM
An interesting idea, but I'm not completely convinced. The idea that life started at hydrothermal vents would not seem to require tides. I've also heard the idea that the moon acted to shield the Earth from some of the planetary impacts and so helped life by preventing extinction events.

Ian Goddard
2004-Mar-22, 10:11 PM
Is it not possible - even *probable* - that said fossils owe to Martian contamination by terrestrial protozoa via similar Earth Ejecta???
That possibility has been considered as an explanation for apparent fossilized bacteria in ALH84001 (http://rsd.gsfc.nasa.gov/marslife/photos.htm). However, in a paper exploring that question McKay et al (2002) (http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1943.pdf) state: "we conclude that we cannot justify the hypothesis that any of the biogenic magnetite is terrestrial contamination."


I'm no statistician - still it seems a concept beyond credulity that organisms should have evolved in so parallel a fashion sans a 'connection'!!!
But we don't have a priori knowledge of how life should or should not evolve among parallel planets. As such, and given our limited range of knowledge, I don't think there exists sufficient basis upon which to establish credulity criteria.

Ian Goddard
2004-Mar-23, 12:09 AM
Is it not possible - even *probable* - that said fossils owe to Martian contamination by terrestrial protozoa via similar Earth Ejecta???
That possibility has been considered as an explanation for apparent fossilized bacteria in ALH84001 (http://rsd.gsfc.nasa.gov/marslife/photos.htm). However, in a paper exploring that question McKay et al (2002) (http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1943.pdf) state: "we conclude that we cannot justify the hypothesis that any of the biogenic magnetite is terrestrial contamination."
Sorry Toutatis, I think I misunderstood your point, which may be: perhaps the apparent Martian bacteria were initially from the Earth, transported to Mars via Earth-impact ejecta, spread on Mars, then sent back to Earth via Martian-impact ejecta. I don't know. :-?

Brady Yoon
2004-Mar-24, 07:32 AM
I disagree with the article. I believe that they are restricting the boundaries of the formation of life too far. Who says that life can't begin on a somewhat harsh environment?

informant
2004-Mar-24, 11:58 AM
No one, I think. As far as I can tell, they're just placing boundaries on the conditions for life to develop in familiar environments.

Mainframes
2004-Mar-24, 12:33 PM
sounds like a good theory, but maybe there would be life expect it would be very simple and not grow well without a moon, some life but not like on Earth. Our moon is very important to the natural cycle of life on earth and its climate. Should we now use our furture SETI projects and radio telescope to search for signals from worlds with moons? This could be a better idea.

The moon is only important to cycle of life because the life on earth has evolved to take advantage of the moon and then eventually became dependant upon it.

IMO if there was no moon, then life would have found other means of timing cycles.

informant
2004-Mar-24, 12:35 PM
You can't know that. I've read some pretty good arguments for the impossibility of life on Earth without the Moon.

Swift
2004-Mar-24, 01:40 PM
You can't know that. I've read some pretty good arguments for the impossibility of life on Earth without the Moon.
Could you give us some examples? Thanks,

informant
2004-Mar-24, 02:13 PM
What if there was no moon? (http://www.badastronomy.com/phpBB/viewtopic.php?t=9196)