The Origins of Directed Panspermia
Scientific American
Guest Blog
January 9, 2013
By Christian Orlic
The Earth is beaming with life and yet there is no consensus on how
life arose or what life is. The origin of life is `one of the great
unsolved mysteries of science’ (Crick, F. Life Itself). While there
is no accepted definition of life, most of us [humans] can easily
discriminate the living from the non-living (IrisFry’s Book is a good
primer on ideas regarding the origins of life). Questions about the
origin of life became more prevalent after Pasteur and others showed
that life did not arise spontaneously.
The discovery that the raw components of life are present throughout
the universe suggests that life could exist elsewhere, and that the
origin of life as we know it may have depended on materials that
arrived on Earth via inter-stellar travel. Some scientists have
speculated that life itself originated elsewhere and made its way to
earth.
In 2012 a movie called Prometheus was released. In this stunning movie
human scholars find similarities between archeological sites from
ancient civilizations separated by centuries have drawn the same
pictogram. The archeologists conclude that the pictogram must be a
map, an invitation, from the `engineers’ who not only designed us but
have intervened in our affairs. The movie is set in 2093 and
researchers decide to go and find them in a quest to further
understand the origins of mankind. Despite its several and severe
scientific flaws, Prometheus is an interesting film because it
addresses that ever mysterious quest to unveil not only how we came to
be but how life began.
Life in space has been making the news, and on November 20th 2012, NPR
reported that NASA’s Mars Curiosity rover had gathered important
data. Mars holds a special place in our world. The principal Mars’
rover investigator, John Grotzinger claimed `This data is gonna be one
for the history books. It’s looking really good,’. He refused to give
any more details because his team had to confirm their findings. In
general, this is good practice because scientists want to avoid
finding superfluous results and correlations; however, in this case,
it heightened suspicion.
Shortly thereafter NASA tried to downplay Grotzinger’s statements,
pointing out that it was the mission which was historic rather than a
specific finding. Despite this backtracking some speculated that
organic compounds had been found, some claimed that it was life that
had been discovered. On December 3rd NASA confirmed, Curiosity had
found Organic compounds but it was uncertain whether they were
indigenous to Mars (or had been brought by Curiosity).
Most of the speculation had suggested that organic compounds were the
`historical finding’. These are also important because they confirm
that the stuff of life, the raw materials, are far more common than
originally thought (as corroborated by the discovery of signs of water
and organic molecules in mercury), or the finding of organic molecules
in meteorites. Like the discovery of extremophiles which showed that
once life got started it could be found in unexpected places; the
advances in the search for extraterrestrial life suggest that the
stuff of life, and hence life, could be commonly found throughout the
universe.
Francis Crick (who co-discovered the structure of DNA with James
Watson) and Leslie Orgel once proposed that life on Earth was the
result of a deliberate infection, designed by aliens who had purposely
fled mother nature’s seed to a new home in the sun. Crick repeatedly
addressed the question of the origin of life between 1971 and 1988 (I
am currently working on a historical study of Crick and Orgel’s theory
of Directed Panspermia and its reception).
Crick and Orgel proposed their Directed Panspermia theory at a
conference on Communication with Extraterrestrial Intelligence,
organized by Carl Sagan and held at the Byurakan Observatory in Soviet
Armenia in 1971. This theory which they described as an `highly
unorthodox proposal’ and `bold speculation’ was presented as a
plausible scientific hypothesis. Two years after the conference they
published an article in Icarusin 1973
().
Crick and Orgel
were careful to point out that Directed Panspermia was not a
certainty; but rather a plausible alternative that ought to be taken
seriously. In the paper Crick and Orgel recognised that they `do not
have any strong arguments of this kind, but there are two weak facts
that could be relevant’. The 1973 paper focuses on the universality
of the genetic code and the role that molybdenum plays in living
organisms (I am likewise working on a history of molybdenum and the
origins of life) which is more than one would expected given the
abundance of molybdenum on the earth’s crust.
Crick and Orgel used the universality of the genetic code to support
the theory of directed panspermia because if life had originated
multiple times or evolved from a simpler genetic code one could expect
living things to use a slew of genetic codes. Further, if there was
only one code, Crick and Orgel reasoned that as organisms evolved they
should evolve to use the same codons to code for different amino
acids.
We can draw a parallel to language: while many human populations use
the same symbols (letters), they combine them in different ways. These
different languages use the same alphabets but different combinations
of the same symbols to denote different objects (French, Italian,
Spanish, Portuguese, Catalan) as opposed to different codes (languages
which uses different alphabets like Spanish and Mandarin); however,
what we find is analog to a single universal language.
Their most convincing argument was the importance of molybdenum in
organic processes and its relative scarcity on Earth. They had argued
that living organisms should bare the stamp of the environment in
which they originated. Organisms, Crick and Orgel held, would be
unlikely to develop a dependency on elements that were extremely rare
as organisms that relied on elements which were more abundant would be
favored by selection. An organisms that was able to substitute the
rare element for one which has similar biochemical properties but is
more frequent would have a clear advantage.
Crick and Orgel pointed out the `anomalous abundance of molybdenum’
in organisms made it possible that life arose in an environment rich
in molybdenum. The abundance of molybdenum in living organisms
suggested that life started in a molybdenum rich environment and they
found that the Earth is not sufficiently rich in molybdenum (this was
later challenged as the amount of molybdenum found in the ocean is
higher than in the Earth’s crust). Thus, they suggest that this
difficulty could be resolved if life began in a molybdenum rich
environment. Likewise, the fact that all organisms use the same codons
for the same amino acids could be explained if life had arisen
elsewhere and the organisms which were used to infect lifeless planets
shared a language.
Crick and Orgel also suggest that the universe is sufficiently old
that other intelligent civilizations could had arisen elsewhere. One
of these other intelligent civilizations could have built a spaceship
and seeded the universe with life. One can easily imagine a not too
distant future where humans accept that our planet and all that lives
within it will perish. In the unlikelihood that this is the only
planet that harbors life in the universe its demise would leave a
lifeless universe.
The demise of our kind is hard enough to accept but the prospect of a
lifeless universe, a universe that could never come to know itself, a
universe so grand and yet with no one to admire it or even dwell in it
could be too much to bare. In order to save our kind we can envision
our zealous and hard working descendants endeavoring to colonize other
worlds (by sending microbes through interstellar
journeys). Microorganisms are easier to transport and could more
readily adapt to new conditions; sending larger organisms would be too
difficult (Crick and Orgel pointed out).
The origins of life remains an unresolved mystery. I argue that Crick
and Orgel’s paper was meant both as a serious and plausible scientific
alternative and as a means to criticize concurrent origins of
life. Considering that life arose elsewhere could also free scientists
studying the origin of life from trying to imitate the alleged
conditions of a pre-biotic Earth. My ongoing research suggests that
while Orgel abandoned Directed Panspermia, Crick continued to advocate
for its viability and to argue in its favor. Our continued exploration
of space will, presumably, continue to reveal the existence of organic
compounds in space (and quite possibly life) and hence suggest that
the universe may be beaming with life.
Images: Mars Curiousity by NASA; Molybdenum by Alchemist-hp at
Wikimedia Commons; Francis Crick and Leslie E Orgel from FASEB
journal.
About the Author: Christian Orlic is currently a graduate student in
Zoology and he is study experimental evolution at Michigan
State. Christian has a BSc in Zoology and one in the History of
Science. Christian is currently working on an extended history of
Crick and Orgel’s theory of Directed Panspermia and its reception by
the scientific community. (I do not quite know what to do for an
author bio). Follow on Twitter @christian_orlic.
From: A. Papazian
http://www.sciencedirect.com/science/article/pii/0019103573901103