Mars
On August 7, 1996, NASA announced a
startling discovery by examining a meteorite that originated on Mars,
they found what they believe is evidence for a primitive form of life that
may have existed on Mars 3.6 billion years ago. More work needs to be done
to confirm this preliminary result, and many scientists remain unconvinced
by the present evidence. But if this preliminary result is confirmed, if
the structures inside the meteorite turn out to be fossil evidence for cellular
organisms, then some important steps can be taken.
First, we would need to launch a mission to Mars, manned
or unmanned, to secure and return to earth core samples that might provide
evidence for or against DNA as the organizing scheme for the Mars life form.
Having accomplished the return of a biological sample and determined the
presence or absence of DNA, we are then faced with a quandary.
If the Mars life form is not based on DNA, it supports
the hypothesis that life is a likely outcome for a planet with the correct
temperature range, atmospheric pressure, liquid water, and sufficient time
with these conditions. This would be a very important finding two
planets with different histories, temperatures, atmospheric makeups and
surface gravity, both producing life through random processes life
based on different models, but life nevertheless.
We could use this result to reinforce the theory that
life is common in the universe. This single data point, the existence of
life of a different form on our sister planet, would greatly aid the theory
that life may be a likely event in a reasonably wide range of planetary
conditions. This finding would re-energize our search for evidence of alien
civilizations.
But if the Mars life form is based on DNA, this is an
equally interesting result, for a different reason because of the
peculiar and ad hoc nature of DNA, and the number of equally viable alternatives
to its specific structure, this outcome would strongly argue for a common
origin for life on Earth and Mars.
It is hard to imagine two independent processes producing
a mechanism such as DNA, especially if the two DNA forms turn out to be
alike in their essential characteristics. It is much more likely that the
two planets somehow shared some early organisms.
This conclusion leads to three likely
hypotheses for DNA sharing:
1. Earth's DNA got to Mars.
2. Mars' DNA got to Earth.
3. Both Mars and Earth were seeded by
some unknown third source.
The third of these alternatives has existed as a theory
for some time. It is called "Directed Panspermia" it proposes
that all life originated from some extraterrestrial source, and (in some
forms of the theory) that life was placed on earth for a reason. This theory
has everything going for it except plausibility and evidence.
The first of these alternatives (Earth to Mars) suffers
from two problems. One, the Mars sample is 3.6 billion years old, earlier
than any direct fossil evidence for life on earth. Two, Earth's atmospheric
pressure prevents an incoming meteorite or asteroid from throwing surface
materials entirely out of the atmosphere and into interplanetary space.
There is evidence that Earth's atmosphere has had similarly high pressures
for a long time period. Thus, it is not obvious how Earth's genetic material
could get into interplanetary space.
The second alternative (Mars to Earth) is the most likely.
Mars may have developed life in an early era of high atmospheric pressure,
relatively high surface temperatures and liquid water. There is abundant
evidence for all these characteristics except conclusive evidence for life.
In this hypothesis, around 3.5 billion years ago Mars'
atmospheric pressure began to drop, and established life forms continued
to exist only below the surface in pockets of liquid water. Then a meteorite
or asteroid impacted on Mars' surface, expelling a large amount of material
from the surface into interplanetary space carrying viable organisms
with it.
The final step in this theory is that some of the Martian
surface material fell into Earth's early oceans, and either successfully
competed with, or provided, Earth's first cellular organisms.
This theory is consistent with the relative age and
conditions of both Earth and Mars, and it is consistent with the age of
the NASA sample, which may, with further work, show that organisms existed
on Mars at a time, 3.6 billion years ago, before there is firm fossil evidence
for life on Earth.
Here are some findings that would be fatal to this hypothesis:
1. If there is firm evidence that Mars' atmospheric
pressure remained high until relatively recently, it would be hard to imagine
how genetic material could leave the surface of Mars in time to provide
Earth with its first DNA.
2. If it turns out that Earth's and Mars' cellular life
forms are based on different principles, this theory has no purpose and
can be set aside.
3. If the ongoing work with the Mars meteorites shows
that there are no cellular structures inside the teasingly shaped cylinders
seen in news photographs, that would also make this theory unnecessary.
If all these dominoes fall, however
if it turns out that there was early Martian cellular life based on
a familiar form of DNA, then it may be that we are all descended from an
ancient Martian cellular life form.
Credits and Biographical note: Paul Lutus has a wide background in engineering
and science. He designed part of the NASA Space Shuttle, then began to develop
computer software. His best-known program was "Apple Writer,"
an early word processor. In research and articles he has explored such topics
as computer mathematics and graphics, and in 1985 he was named Scientist
of the Year by the Oregon Academy of Science.
