[ExI] Life must be everywhere!

[Kelly Anderson]

On Fri, Apr 13, 2012 at 4:14 AM, Anders Sandberg <anders at aleph.se> wrote:
> 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.

Anders, while I agree with you that the impact itself would probably
kill a lot of bacteria, microbes are in the rocks a considerable
distance down. Estimates range from 3km at a low (they actually found
stuff at 1.6 miles) to a high of 7km where it would be too hot even
for the most heat loving bacteria we know of. (I wouldn't be surprised
if life surprised us by living deeper than we currently think of as
possible, by the way... as Micheal Crichton said, "Life will find a
way"...)

http://en.wikipedia.org/wiki/Endolith
http://microbewiki.kenyon.edu/index.php/Deep_subsurface_microbes

Some theorists believe this is where life first evolved, in fact. Many
of these microbes have exceptionally slow metabolism, dividing as
little as once per century! They seem therefore very apt to be able to
survive in outer space.

I don't know how deep the crater was... was it over 7 km deep?

In addition to that, if you look at surviving rock from nuclear test
sites, what you find that while there is a core of silica glass near
the impact/explosion zone, that further out you get shocked quartz...
the closer it is to the blast, the more "shocked" it is. One page I
read indicated that shocked quartz is an indication of lots of
pressure, but not as much heat as you might imagine. Think about heat
transferrence through rock... it takes time... we're talking something
that happened in a matter of seconds or a few minutes at most... And
while there was a huge heating effect globally because some rocks were
super heated, many rocks further from the blast zone would not be.

In fact, I hypothesize (without factual basis) that you might even get
some rocks that would be encased with a little bit of a glass or
melted layer, providing further protection for any microbes further
inside a stone.

> I don't think anybody
> knows how to calculate the denaturating effects, but they are likely severe.

Undoubtedly, but we have recently learned that they can withstand
20,000 Gs of shock, which is rather amazing! I would bet if you were
to look back in the atomic underground testing data, you could find
data on the survival of microorganisms, though I don't know if they
knew to look for bugs in rock back then.... so maybe not.

> 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.

The top kilometer should be increased to at least three for your
computation here Anders.

> 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 heard on the radio (Michio Kaku) that Kepler scientists now believe
there is one earth like planet for about every 200 stars... another
element of the equation reduces to scientific knowledge, or at least a
well educated guess.

-Kelly