I am concerned that the trend of establishing
quantitative targets or assessments for academic research
results, such as "Japan should win a certain number of Nobel
Prizes in the following XX years," is increasing too much
in our society today. Therefore, I hesitate to start with
numbers, but I have counted and classified the scientific
fields on the pictures of front covers of sixty copies, published
in about one year, of "Science" and "Nature", magazines that
cover a wide range of scientific fields. Weighing the value
by the number of front cover pictures is not consistent with
my daily approach where I loudly scold my own child for being
carried away with comic books, and encourage my child to read
real books. Nevertheless, my results are 60% for biology;
23% for space/planets/earth; 9% for material science/chemistry/material;
and 4% for fundamental physics. Biological sciences in space
are related to two fields, biology and space/planet/earth,
and I would insist on its importance by citing the front covers.
But, rethinking that biological sciences in space can be the
product set of these two fields, I would like to explain what
its central themes are. The title above is a catchphrase using
simple words that modify the main theme, "Exploring Extraterrestrial Life and Understanding Life with
Different Principles", of the opening lecture of the Japanese
Society for Biological Sciences in Space (JSBSS) held in November
2003.
Search for life in space
All living things have parents, and their
parents have parents. In this way, there is no spontaneous
generation. If this is true, we must draw a picture of how
life first originated on earth or other celestial bodies as
a process following chemical evolution in space history and
interstellar space. The artificial synthesis of parasitic
viruses has already been reported, but the perfect synthesis
of cellular life forms, which can maintain their own autonomous
lives, has not yet been achieved. The more the life mechanism
of cells is elucidated, the more a major missing link between
pre-biotic precursors and primitive cells is recognized. As
for the origin of life, there is a hypothesis that meteorites,
which were generated in interstellar space and contained many
precursors, landed on earth and, then, reacted with water,
creating all the components of life forms at once in a high
density. Also, research is now being carried out seeking a
model of life in the highly specific physical and chemical
environment around the deep-sea hydrothermal vents. Earth¬s
very active crustal movements have erased information about
the primitive life forms and the environment that generated
primitive life. The reason why we search for life in space
is to answer the question whether or not life forms exist,
or existed, on celestial bodies other than Earth, and to respond
to expectation of discovering life¬s origin and its environmental
conditions.
Living things on Earth, which have evolved
into many kinds of life in a variety of forms, can be traced
back to common ancestor. Living things on Earth have conservatively
inherited mechanisms and biochemical materials that were once
obtained. There are cases as if living things arbitrarily
select, for example, which optical isomer should be selected
to form their bodies and what combination of amino acids should
be used. Concerning the elements composing living things,
we can find the composition corresponding to the solar system
and its planet, Earth. The COSPAR life science section called
the study to explore if the principle of life on Earth is
limited to Earth with focusing on defining factors which Earth
as a planet has given for the origin and evolution of living
things as Planetary Biology. Even if the combination of elements
composing living things varies, species and evolution, which
are the fundamental concepts of biology, may be the universal
principles for life from the viewpoint of space. It is effective
to search for life on other celestial bodies and compare it
with life on earth in order to scientifically verify this
hypothesis. For this purpose, it may be a faster way to discover
living species, of which ancestors are different from other
living things, in the isolated environment on earth.
Sensation of Mars meteorites
The report on meteorites estimated to have
originated on Mars, which were collected in Antarctica, has
provided a major impact on research and caused us to think
this over. Some new findings indicating the possibility of
life on Mars were found in the meteorites. One finding is
the structure, which looks like a trace fossil of microorganism,
shown in the cleaved surface of the meteorites. Many scientists
pointed out that the physical size of the structure is far
smaller than that of bacteria on earth. The biggest focus
of our research is to explore living things that stand on
different principles from living things on earth. So, it is
ironic that scientists criticize that living things on Mars
are different from those commonly seen on earth.
With this argument continuing, a workshop was held in the
U.S.A. to conjecture the size of the smallest living things.
The information amount required for autonomous, not parasitic,
living things to maintain their life and make autoreproduction
was estimated, and then translated to the amount of molecular
coding such information. Further, mechanisms to develop information
and cell membranes, boundaries for dividing oneself from others,
were added, and the limits on the sizes of living things were
examined. The work was to inversely assemble life, to build
living things from information already known. The estimated
size was not largely different from that of mycoplasma, which
is the smallest autonomous living thing known. Cellular organs
constructing cells were once independent living things respectively.
Some time in the past they were taken in and began to live
symbiotically. The workshop concluded that, if we seek small
living things, we should envision a world where cellular organs
were independent living things and some living things symbiotically
maintained life. In order to discover and understand living
things standing on entirely different principles, needless
to say that we should base our work on an in-depth understanding
of life, we should maintain free thinking that is not constrained
by established knowledge.
|