[ExI] Life must be everywhere!

Tomasz Rola rtomek at ceti.pl
Sat Apr 14 16:29:31 UTC 2012

On Fri, 13 Apr 2012, Anders Sandberg wrote:

> ? wasn't too convinced by the paper because it mostly counted rocks rather
> than cells. The authors were much more interested in how many pebbles could
> get from point A to B than what was in them.
> Let's assume 90 kg/m^2 of biomass (double a tropical forest; I am assuming
> just as much biomass in the lithoautotropic ecosystem as on the surface to be
> optimistic). They suggest that ejecta amounting to 30% of mass of the impactor
> (sounds *very* optimistic!). So some 0.3*pi*5000^2*90=2.1e9 kg of biomass ends
> up in space (5000 from the radius of the impact site). The ejected total mass
> is 3*10^14 kg, so the fraction that is biomass is 7e-6 - that would indeed
> allow a few hundred million bacteria on each 1 cm pebble.
> However, much of this material will be subjected to denaturating temperatures
> (it was a 96 teraton explosion), and worse, the distribution of cells is
> uneven: the vast majority of material will be from deep crust and the impactor
> itself, both which are likely cell-free. I don't think anybody knows how to
> calculate the denaturating effects, but they are likely severe. The uneven
> distribution on the other hand might be roughly approximated: if we assume the
> ejecta is an equal mix of impactor and the same volume of Earth, that only the
> top kilometer of rock is life-bearing, and that pebbles keep together, the
> fraction of ejecta that is from the life layer is (pi*5000^2*1000) /
> (4*pi*5000^3/3)=0.15 - just 15% of the pebbles will have cells, the rest are
> from impactors or deep crust.
> I certainly cannot rule out panspermia this way; life can be amazingly hardy,
> and it is enough to just get a few cells into a survivable environment for
> them to spread. But I suspect the denaturation of impact is a massive factor
> that reduces the viability of launched pebbles even before they are subjected
> to space conditions. If the denaturation reduces the number of viable pebbles
> by just two orders of magnitude (which sounds eminently likely), then a
> thousand pebbles reaching Gliese 581 will not transfer life. The numbers
> within the solar system still seem to be high enough to allow transfer (and KT
> was just one recent big impact), so if it is possible I expect local
> panspermia to have occurred.

I was thinking of the other end of this "pan-sperm adventures", i.e. 
landing on a remote body. Escape velocity for Solar System is 525 km/s. 
This is how fast - at a minimum - an ejecta will have to go to make it 

One can play with impact effect calculator, here:


to see how hard (or maybe easy) actually it is going to be for any life to 
survive an impact with Earth-like planet. I assume if I could got burned 
alive standing at 100 km distance from impact of 1km-radius iron body 
running at 525 kmps, the effect is like quite a big nuclear weapon blast. 
How much life survived at test epicenters? Without looking for data, I 
guesstimate everything close to impact will get sterilized.

So much about naturally happening panspermia.

Tomasz Rola

** A C programmer asked whether computer had Buddha's nature.      **
** As the answer, master did "rm -rif" on the programmer's home    **
** directory. And then the C programmer became enlightened...      **
**                                                                 **
** Tomasz Rola          mailto:tomasz_rola at bigfoot.com             **

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