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a spacecraft
cruises silently through the outer
spiral arm
of the milky way
these voyages from lands far away aren't
in a hurry
traveling at just 60 000 miles an hour a
crawl
by cosmic standards
but they've kept their pace for a
million years
journeying by several thousand star
systems
over a distance of a hundred light years
and each new star system they pass they
scan
searching for the perfect combination
that they're looking for
a lifeless new planet around a young
yellow sun
circling in on their long sought after
quarry
passing close by to the planet's surface
they deploy their ancient
payload
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dropping shielded through the atmosphere
to land on the surface
disgorging its contents
inside is a 1 000 kilogram payload of
bacterial samples
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100 different types each varied and
suited
to a different environment
a few immediately perish on the surface
of this new planet
the chemistry and conditions all wrong
but the ones that survive find a habitat
ripe for the taking they not only
survive
but thrive quickly moving to colonize
the surface
and they evolve adapting to new niches
exploiting brand new environments
over the next four billion years or so
while the yellow sun
brightens overhead they evolve into ever
more
complex forms
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until eventually they evolve into
conscious
creatures beings that are self-aware
with culture and philosophy science
mighty civilizations rise and fall eons
and golden ages coming and going
until finally for the first time these
colonists
can give their home a name
earth
this origin story might sound like
science fiction
but it's a real credible scientific
theory
first proposed in the 1970s by one of
the discoverers
of dna francis crick
it's just one of the options for the
phenomenon known as
panspermia an alternative
extraterrestrial hypothesis for how life
on earth began
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panspermia a term stemming from ancient
greece
directly translates to all seeds
it describes the idea that the seeds of
life spread by distribution
throughout the universe either
accidentally
or manually driven germinating and
spreading wherever it finds
a likely host planet
it's more than a fringe theory too and
not considered
pseudoscience
panspermia is something scientists have
been coming back to
for hundreds of years
in 1903 it was swedish chemist svante
arenas
who first suggested that spores could be
driven across the expanse of space
by the pressure of solar radiation
and by 1957 it was again suggested that
life on earth
came from another planet as an
aggressive
infection
an alternative concept was proposed in
1960
that earth life was the byproduct of
cosmic garbage
organic detritus left behind by an older
much more advanced
civilization and as we have learned
in the 1970s francis crick entertained
the possibility
of intentional directed panspermia
it's something we can imagine doing
ourselves to seed other planets with the
template
of our own ecosystems
finally by the 1980s eminent
mathematician
chandra wikramsing went so far as to
suggest that
viruses might have rained down from
interplanetary space
and thus responsible for brand new
epidemics on the one hand
and boosts in evolution on the other
theories of panspermia find credence in
the evidence from the early earth
by all reckoning our planet's first half
billion years or so
were a violent tumultuous time
it was a truly inhospitable place for
life to begin
and yet begin it did
remarkably rapidly after the end of the
hellish haitian
certain compounds like sugars and amino
acids require the conditions of a solar
nebula to form
and are delivered to a planet's surface
by the relentless solar wind
undoubtedly some of the ingredients for
life did come
from space in what is sometimes known as
soft
panspermia
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in 2004 the stardust mission
flew a special sample collecting gel
through the tail of a comet
and returned it to the earth inside that
gel
scientists found amino acids and other
organic compounds essential to life
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it's likely that these cosmic chemicals
accreted
along with the earth and have been
raining down gradually
ever since
but although modern scientists can begin
to identify
parts of the molecular puzzle and
describe how life could have arisen from
the basic building blocks available at
the planet's surface
that puzzle has yet to be fully solved
the true origin of life on earth is
still a mystery
so then it seems almost natural to ask
could it have originated
somewhere else
could microorganisms have been seeded on
the earth
not long after its formation either
intentionally
or accidentally the directed panspermia
posited by crick
is certainly possible our earth is just
four and a half billion years old but
the universe
is more than three times as ancient
star systems that formed early on in the
universe's history could host
civilizations much older and more
advanced
than our own
so while we don't yet have the
technology for an interstellar seeding
mission
it's conceivable that such a technology
could be developed
with time
and yet with only one living planet that
we know of right now
evidence for directed panspermia is
lacking
instead passive panspermia is a
hypothesis we can give substance to
with our knowledge of physical processes
ongoing in the solar system
today
there is evidence that life could
accidentally have been seeded across the
cosmos
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for a living being to travel from one
celestial body to another
they must survive three trials
escape transit
and delivery
first they must escape their host planet
while we are firmly rooted to the ground
or the lower layers of the atmosphere at
least
microorganisms are more flighty
small enough to be moved by atmospheric
forces
moved upwards by thunderstorms and
volcanic eruptions
they can travel right to the top of the
atmosphere where
it's assumed it's easier for them to be
whipped away by the solar wind
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beginning what could be a near endless
journey
through the heavens
or they could escape by the catastrophic
forces that jeopardize life on the
surface
large enough asteroids can shatter
surface rocks
scattering them upwards out into space
if those rocks contain microbes then
they could very well become
tiny spacecraft manned by a bacterial
crew
the next challenge is to survive the
journey through space
a cold dry vacuum awash with deadly
radiation
space is not a friendly place for life
and the sheer distance between planets
and near endless void of inhospitable
wasteland
means that any bacterial travelers face
a long
journey depending on their heading and
destination the trip could last millions
of years
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over the last few decades since humanity
took to the solar system
scientists have conducted plenty of
experiments on board satellites and
spacecraft
to see how well earth's bacteria could
survive
in the vast reaches of space
it turns out that many microbes are able
to protect themselves against the cold
and dry conditions
in a primitive form of cryostasis
as inactive spores
but uv and cosmic radiation remains a
threat
even to dormant spores
having the power to break and distort
the genetic material
inside the cells killing them outright
or mutating them beyond recognition
so some shielding is needed
and if not in a specially designed
spacecraft then a simple rock
will suffice
the radiation cannot pass far through
solid rock
so microbial passengers contained within
could weather the cosmic storm
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but these interplanetary voyagers have
one final challenge
before they can become the colonists of
a new world
they must survive the landing
meteors raining down on earth experience
intense heating
and a shock of impact that is enough to
melt solid rock
could a simple life form possibly
survive
this too has been tested by modern
scientists by shooting bacterial samples
through a powerful
air cannon the survival of these spores
suggests that under the right conditions
microbes could indeed survive a landing
encased in their protective rock armor
for a million years
and when the dust finally clears the new
world
is theirs to call their own
so evidence on earth suggests that life
could indeed have survived a trip
through space but evidence that it
actually did
and this is how the seeds of life were
delivered to earth almost 4 billion
years ago
is lacking the potential evidence
has simply been lost to the mists of
time
to plate tectonics and the recycling of
the earth's surface
some would argue that this is a moot
point anyway
if during the first years of our world
some four billion years ago
living beings arrived on earth from
another planet it only shifts the
question
of the origin of life to a different
location
and one we know even less about than the
early earth
life must have begun somewhere
but since we still don't have all of the
answers for how life got started here
then another planet another environment
could hold the key
another planet could be host to some
factor that makes the spontaneous
generation of life
much more likely
and today we are discovering thousands
of new exoplanets in orbit around alien
stars
for the first time we can probe these
extraterrestrial environments
in search of answers
we may yet find francis crick's advanced
civilization
as gods creating species in their image
throughout the cosmos
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but until life is found on another
planet
we will never truly know whether we are
children of the earth
or of the universe
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