Marine Ecosystems Research Department - jamstec japan agency ...

JAMSTEC 2002 Annual Report
Marine Ecosystems Research Department
veyed the state of the current to determine the process of
seawater exchange in Sekisei Lagoon. From this, we
estimated that the exchange of seawater takes about ten
days. Our survey on the current carried out during the
coral spawning period suggests that it takes several days
for coral eggs and larvae to flow out to the open ocean
from within the lagoon depending on the spawning area.
At the same time, we were able to ascertain the synoptic
circulation pattern of Sekisei Lagoon. These results
were presented in Japanese scientific journals, and at
international conferences and symposiums.
Search for micro-pore filters available for use under
high temperature and high pressure conditions
Period: FY-FY
"Chemical Evolution" is the process of chemical
changes from inorganic to organic substrates prior to
the origin of life.
Various experiments have been done to show certain
aspects of this process; the first of which is called
Miller's experiments done by Miller in . In this
experiment, water (H O), methane (CH ), ammonia
(NH ) and hydrogen (H ) were used as the gaseous
components that were believed to be present on the
early earth. These chemicals were all sealed inside a
sterile array of glass tubes and flasks, and were heated
(in place of volcanic activities) and subjected to electrical
discharges (in place of lightning). This experiment
showed that organic compounds such as amino
acids, which are essential to cellular life, could be
made easily under the conditions that were believed to
be present on the early earth. However, recent studies
showed that the atmosphere of the early earth was an
oxidizing environment unlike Miller's experiment conditions
and that in such oxidizing conditions, it is quite
difficult to synthesize any organic substrates.
Since the discovery of deep-sea hydrothermal vents
in the Galapagos Rift in , many scientists have
been considering that such an environment could be a
possible candidate for Chemical Evolution. The reasons
are as follows:
() High temperature energy for chemical reactions
() Reducing environment required condition for
inanimate syntheses of organic substrates
() High concentration of heavy metals catalysts
for chemical reactions
A large number of in vitro experiments have been
conducted to investigate this possibility. Several types
of amino acids were synthesized under artificial
hydrothermal vent conditions. Spherical structures
composed of membranes also appeared under such
conditions. However, these experiments were performed
using limited trace elements under limited
fluctuation conditions within a limited time frame.
In situ experiments on Chemical Evolution at deepsea
hydrothermal vents are expected to show novel
reaction processes and products but there has been
no previous attempt because of the difficulty of
access to deep-sea vents and in developing an in situ
experimental device. Here we began to search for
micro-pore filters that are the most important components
of the in situ device. The filters must have tolerance
to high temperature and high pressure, be permeable
to small molecules like the inorganic substrates
derived from vent fluid, and prevent synthesized
large organic molecules from flowing out of the
reaction chambers.
In fiscal we carried out in situ experiments on
micro-pore filters at hydrothermal vents on Hatoma
Knoll in the Okinawa Trough. We positioned the test
devices at the hydrothermal vent with a maximum
temperature of ˚C. We recovered the devices about
a week later and found a large amount of hydrothermal
deposits we assume to be sulfide attached to the
inside of the filter chambers (Fig.). We also found
that the titanium parts making up the devices had not
corroded at all.
The silicon nitride filters in the in situ testing units
showed no noticeable deformation, and had uniformly
turned black. Internally, the eight filter units were
deformed in that they all showed signs of partial
fusion (Fig.).
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