[meteorite-list] Did Life Arrive Before the Solar System Even Formed?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed May 4 17:33:26 2005
Message-ID: <200505042132.j44LWrk14429_at_zagami.jpl.nasa.gov>

http://www.universetoday.com/am/publish/lithopanspermia.html

Did Life Arrive Before the Solar System Even Formed?
Written by Jeff Barbour
Universe Today
May 4, 2005

Summary - (May 4, 2005) The theory of panspermia proposes that life
really gets around, jumping fron planet to planet - or even from star to
star. Life might be everywhere! Assuming this is true, how do
single-celled bacteria make the journey through the vacuum of space?
Easy, they use chunks of rock as space ships, in a process called
lithopanspermia. And now, researchers from Princeton and the University
of Michigan think that life carrying rocks might have been right there
at the beginning of our solar system, keeping their tiny astronauts safe
and sound, frozen in statis until the planets formed and the right
conditions let them thaw out, stretch their proteins, and begin a
process leading from microbe to mankind.

Full Story - Things seem to start simple then get more complex. Life is
like that. And perhaps nowhere is this notion truer than when we
investigate the origins of life. Did the earliest single cell
life-forms coalesce from organic molecules here on Earth? Or is it
possible that - like dandelions wafting spore above spring grass -
cosmic winds carry living things from world to world later to take root
and flourish? And if this is the case, how precisely does such a
"dia-spora" occur?

450 years before the common era, Greek philosopher Anaxagoras of Ionia
proposed that all living things sprung from certain ubiquitous "seeds of
life". Today's notion of such "seeds" is far more sophisticated than
anything Anaxagoras could possibly envision - limited as he was to
simple observations of living things such as budding plant & flowering
tree, crawling & buzzing insect, loping animal or walking human; not too
mention natural phenomena like sound, wind, rainbows, earthquakes,
eclipses, Sun, and Moon. Surprisingly modern in thought, Anaxagoras
could only guess as to the details...

Some 2300 hundreds years later - during the 1830s - Swedish chemist J?ns
Jackob Berzelius confirmed that carbon compounds were found in certain
meteorites "fallen from the heavens". Berzelius himself however, held
that these carbonates were contaminates originating with the Earth
itself - but his finding contributed to theories propounded by later
thinkers including the physician H.E. Richter and physicist Lord Kelvin.

Panspermia received its first real treatment by Hermann von Helmholtz in
1879, but it was another Swedish chemist - 1903 Nobel Prize winning
Svante Arrhenius - who popularized the concept of life originating from
space in 1908. Perhaps surprisingly, that theory was based on the notion
that radiation pressure from the Sun - and other stars - "blew" microbes
about like tiny solar sails - and not as the result of finding carbon
compounds in stony meteorite.

The theory that simple forms of life travel in ejecta from other worlds
- embedded in rock blasted from planetary surfaces by the impact of
large objects - is the basis for "lithopanspermia". There are numerous
advantages to this hypothesis - simple, hardy forms of life are often
found in mineral deposits on Earth in forbidding locales. Worlds - such
as our own or Mars - are occasionally blasted by asteroids and comets
large enough to hurl rock at speeds exceeding escape velocities. Mineral
in rocks can shield microbes from shock and radiation (associated with
impact craters) as well as hard radiation from the Sun as stony meteors
move through space. The hardiest forms of life also have the ability to
survive in a cold vacuum by going into stasis - reducing chemical
interactions to zero while maintaining biological structure well enough
to later thaw and multiply in more salubrious environs.

In fact several examples of such ejecta are now available on earth for
scientific analysis. Stony meteors can include some very sophisticated
forms of organic materials (carbonaceous chondrites have been found that
include amino and carboxylic acids). Fossilized remnants from Mars in
particular - though subject to various non-organic interpretations - are
in the possession of institutions such as NASA. The theory and practice
of "lithopanspermia" looks very promising - although such a theory can
only explain where the simplest forms of life come from - and not how it
originated to begin with.

In a paper entitled "Lithopanspermia in Star Forming Clusters" published
April 29, 2005, cosmologists Fred C. Adams of the University of Michigan
Center for Theoretical Physics and David Spergel of the Department of
Astrophysical Sciences of Princeton University discuss the probability
of carbonaceous chondrite distribution of microbial life within early
star clusters. According to the duo, "the chances of biological material
spreading from one system to another is greatly enhanced ... due to the
close proximity of the systems and low relative velocities."

According to the authors, previous studies have looked into the
likelihood that life-bearing rocks (typically exceeding 10 kgs in
weight) play a role in the spread of life within isolated planetary
systems and found "the odds of both meteroid and biological transfer are
exceedingly low." However "odds of transfer increase in more crowded
environments" and "Since the time scale for planet formation and the
time that young stars are expected to live in birth clusters are roughly
comparable, about 10 - 30 million years, debris from planet formation
has a good chance of being transferred from one solar system to another."

Ultimately Fred and David conclude "young star clusters provide an
efficient means of transferring rocky material from solar system to
solar system. If any system in the birth aggregate supports life, then
many other systems in the cluster can capture life bearing rocks."

To arrive at this conclusion, the duo performed "a series of numerical
calculations to estimate the distribution of ejection speeds for rocks"
based on size and mass. They also considered the dynamics of early star
forming groups and clusters. This was essential to help determine rock
recapture rates by planets in neighboring systems. Finally they had to
make certain assumptions about the frequency of life-encapsulated
materials and the survivability of life-forms embedded within them. All
this led up to a sense of "the expected number of successful
lithopanspermia events per cluster."

Based on methods used to arrive at this conclusion and thinking only in
terms of present distances between solar systems, the duo estimated the
probability that Earth has exported life to other systems. Over the age
of life on Earth (some 4.0 Byr) Fred and David estimate that the Earth
has ejected some 40 billion life-bearing stones. Of the estimated 10
bio-stones per annum, nearly 1 (0.9) will land on a planet suitable for
further growth and proliferation.

Most cosmologists tend to address the "hard-science questions" of the
origin of the Universe as a whole. Fred says that "exobiology is
intrinsically interesting" to him and that he and "David were summer
students together in New York in 1981" where they worked on "issues
related to planetary atmospheres and climate, issues that are close to
questions of exobiology." Fred also says that he "spends a healthy
fraction of research time on problems associated with star and planet
formation." Fred acknowledges David's special role in thinking "up the
idea of looking at panspermia in clusters; when we talked about it, it
became clear that we had all the pieces of the puzzle. We just had to
put them together."

This interdisciplinary approach to cosmology and exobiology also led
Fred and David to look at the question of lithopanspermia between
clusters themselves. Again using methods developed to explore the
proliferation of life within clusters, and later applied to the
exportation of life from the Earth itself to other non-solar system
planets, Fred and David were able to conclude that "a young cluster is
more likely to capture life from outside than to give rise to life
spontaneously." And "Once seeded, the cluster provides an effective
amplification mechanism to infect other members" within that cluster itself.

Ultimately however, Fred and David can not answer the question of where
and under what conditions the first seeds of life took form. In fact,
they are willing to admit that "if the spontaneous origin of life were
sufficiently common, there would be no need for any panspermia mechanism
to explain the presence of life."

But according to Fred and David, once life gets a foothold somewhere, it
manages to get around quite handily.
Received on Wed 04 May 2005 05:32:53 PM PDT