On the origin of life

On the origin of Life:  
An interesting news item popped up this morning. A Professor Chandra Wickramasinghe, Director of the Cardiff Centre for Astrobiology, who first propounded the theory of panspermia with Sir Fred Hoyle, claims absolute proof that the first microbes were deposited on Earth 3,800m years ago.  

He's not the only one to hold this belief. The venerable Francis Crick also held the idea that life was seeded from "out there". You can check it out at: 

http://news.bbc.co.uk/2/hi/uk_news/wales/south_east/8491398.stm  
 
The idea is not so far out actually. Astronomers have confirmed that gas clouds out there do contain organic molecules, and biologists keep finding extremophiles here on earth all the time.  I find it very curious that virtually ALL life on earth is based on the one blueprint... DNA. You'd think that more than one mechanism would have evolved, but not so, on this world so full of diverse life, DNA is all there is. Of course, pushing the problem out into outer space doesn't really solve it. If the first DNA molecules came drifting down from some interstellar gas cloud, why wouldn't some other kind of "life molecules" drift down as well? or is there only one kind out there too? or is it such a rare event that it only happened once in our 4 billion year history? 

Since it did apparently happen 3.8 billion years ago, rather early in the earth's history, one would rather expect it to have happened again, or is it just coincidence that it happened early in our history? The Drake Equation would indicate that such an event is very rare (although it refers to intelligent life only, and is, at best, just a guess).


The Drake equation states that:

where:

N = the number of civilizations in our galaxy with which communication might be possible;

and

R^* = the average rate of star formation per year in our galaxy

f_p = the fraction of those stars that have planets

n_e = the average number of planets that can potentially support life per star that has planets

f_ℓ = the fraction of the above that actually go on to develop life at some point

f_i = the fraction of the above that actually go on to develop intelligent life

f_c = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L = the length of time such civilizations release detectable signals into space.