[meteorite-list] Panspermia and Mars back contamination

[Chris Peterson]

Our bodies are extremely difficult environments for microbes- much worse 
than, say, a geothermal vent a few miles down. Your suggestion that Martian 
microorganisms might have a feast when presented with humans should apply 
equally well to Earth organisms, most of which have never encountered us and 
could potentially use us as hosts. But in fact, Earthly microorganisms 
normally don't do that. We can enter all sorts of unusual environments here, 
and be exposed to millions of new kinds of microbes, and not encounter any 
that are pathogenic.

I think (and I know its a pretty commonly held opinion by exobiologists) 
that the likelihood of a microbe that evolved on another planet being 
pathogenic is extremely small. But not zero, of course, which is why the 
possibility shouldn't be ignored.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "Mexicodoug" <mexicodoug at aim.com>
To: <clp at alumni.caltech.edu>; <meteorite-list at meteoritecentral.com>
Sent: Saturday, June 06, 2009 2:20 AM
Subject: Re: [meteorite-list] Panspermia and Mars back contamination


"Pathogens and their hosts are, quite literally, made for each other."

I understand this statement but disagree with it in the terms of the
current debate. It presupposes our thoughts from our experience with
life on earth and the equilibrium life has here. At a basic level we
are just bags of sugars, proteins and fats. Detritus on earth can be
eaten by millions of organisms - just about any organic materials and
then there are even critters that can deal with sulfur and nitrogen
bases in extreme environments.

How many microorganisms can live in detrital composts on Earth? What
prevents them from eating organisms that are alive? It is more a one
way protection developed by the living host in this convergence, but
not necessarily a handicap for the invasive. If the host had no basis
for an immune response, microorganisms would eat people alive just as
easily as detritus on Earth, like the massacre that happened during the
Spanish Conquest of Native America.

I guess the question you might raise is: But if Martian microbes had
nothing like flesh to eat how would they suddenly become human
flesh-eating nanobacteria or whatever, here? Given the harsh Martian
environment they ought to be fairly omnivore and if we are presupposing
some kind of cellular life (this being subject to another debate) I
don't see it as far fetched. Really, if the "Martian pathogen" found
anything at all to eat on the smorgasbord of
 earth it could trash our
ecosystem by hitting any level of our equilibrium without being harmful
at all directly to humans. It might even be passive and like our oceans
and be super-photosynthetic, and as an example peacefully co-exist
except for non-stop peeing of cyanide or something such, into the
oceans...a la movie Sunshine (2007), the greenhouse in the Icarus 1.

Best wishes,
Doug

PS, the good thing is ... scientists, instead of our immune systems,
probably could devise treatments fairly easily, pretty much due to the
absence of "being made for each other" (= able to fight back via
convergent evolution) cited.