FOR three hours there was blackness. Then, on their monitors nearly 11
kilometres above the ocean floor, engineers and scientists saw the orange-green
sludge that marked the deepest part of the deepest trench in the world. Sediment
swirled upwards, just as lunar dust had shrouded the Eagle during man鈥檚 first
landing on the Moon, and the tiny craft Kaiko rested its legs on the bottom of
the Marianas Trench in the Philippine Sea. In the control room of Kaiko鈥檚 mother
ship there was unrestrained . . . nonchalance.
The Japanese scientists who had achieved this feat admit that their emotions
were subdued. 鈥淓xploring the oceans is a bit like cooking lunch,鈥� says geologist
Kanataro Fujioka. 鈥淵ou eat one meal, and then you move on and start cooking the
next one.鈥� Senior researcher Shin鈥檌chi Takagawa has an equally unromantic but
more succinct way of summing up the achievement. 鈥淏ottom,鈥� he shrugged, 鈥渋s
bottom.鈥� Such self-effacement may be the Japanese way of not appearing to gloat
over what was a triumph of exploration. Even the unmanned exploration craft
developed by the Japan Marine Science and Technology Centre (JAMSTEC) has an
unromantic name: kaiko simply means trench.
The submersible is part of the Deep Star programme to explore uncharted parts
of the world鈥檚 oceans. Kaiko, which can dive deeper than any of JAMSTEC鈥檚 other
craft, took seven years to develop. It first went to the Marianas Trench in
February 1994, loaded aboard its mother ship Yokosuka, from which it descended
to the depths, sending data via a protected fibre-optic line. At around 9000
metres, Kaiko split into two. The smaller craft slung from Kaiko鈥檚 underbelly
descended further into the blackness. Halogen lights picked up nothing but the
continuous drizzle of submarine snow, detritus from the ocean falling to the
bottom. As the smaller Kaiko continued to descend, the video cameras picked out
a murky desert of sand and mud. Then, with just a few metres to go before
touchdown, disaster struck. 鈥淪uddenly our screens went blank,鈥� says Takagawa. 鈥淚
turned pale. We had lost the signal from Kaiko.鈥�
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The engineers worked frantically to restore contact, but the screens just
flickered with static. Close as the submersible had come to the bottom, they
decided to haul it back up. Despite the lack of a visual signal, they ordered
Kaiko to leave a marker behind. 鈥淚t took six months to identify the problem,鈥�
says Takagawa, 鈥渁nd then another three months to make a new cable. By January,
we were ready to go down again.鈥�
The Marianas Trench is a geological phenomenon, the point at which two parts
of the Earth鈥檚 crust collide. The Pacific Plate dives beneath the Philippine Sea
Plate, dragging part of it down towards the mantle and forming an underwater
valley 4 kilometres deep, in a part of the ocean that is already several
kilometres deep. If Mount Everest were tipped upside down its peak would not
reach the bottom of the Marianas Trench.
With its new cable on board, Kaiko was lowered into the ocean depths for a
second time in March 1995. Once again, the two parts of the craft separated just
above the ocean floor. This time there was no mistake. The bottom loomed into
view, just a few metres from where Kaiko had left its marker the previous year.
The craft landed gently in the deepest depression on the trench floor, a record
10 911 metres beneath the surface. 鈥淭here was no cheer in the control room,鈥�
Takagawa recalls. 鈥淓veryone was very quiet. Personally, I was far too involved
with the engineering to raise a cheer. But we all had a feeling of
yatta!鈥攚e鈥檝e done it.鈥�
Just over a year later, JAMSTEC is disclosing some of the details of what it
found so far below the surface of the Philippine Sea. Sitting in a conference
room at JAMSTEC鈥檚 headquarters in Yokosuka, Takagawa and Fujioka begin to play
videotapes of that first touchdown. Takagawa points at the screen, indicating a
very weak but steady current on the ocean floor, which moves the suspended
detritus slowly across the screen. 鈥淢y greatest hope was that we would see
animals down there, and we did. This was the first thing we saw after Kaiko
touched bottom.鈥� He flattens his finger on the screen below a small, white
object manoeuvring close to a piece of fish bait that Kaiko brought down with
it. The white object turns out to be a sea cucumber. 鈥淲e were very pleased to
see that. We hadn鈥檛 expected it.鈥�
It soon becomes clear that even the deepest part of the deepest ocean
contains life. Kaiko鈥檚 video camera also captured a scale worm drifting slowly
nearby. Despite the presence of two lonely-looking animals, to human eyes the
Marianas Trench looks almost dead. In fact, the sediment is teeming with life,
and the microbiologists had a field day.
鈥淲e brought up six mud samples from the bottom,鈥� says microbiologist Koki
Horikoshi, 鈥渁nd we found that there were about a million bacteria in a gram of
dried mud. That鈥檚 not a small number, even though it鈥檚 about a hundredth or a
thousandth of what you would find in ordinary garden soil. We found conventional
bacteria, but we also found some very interesting microbes.鈥�
Among the surprises, says Horikoshi, were large numbers of thermophilic
bacteria, which, as their name suggests, normally live in much hotter waters
than these. The temperature at the bottom of the trench is a frigid 2.3 掳C.
Horikoshi is now studying the relationship between temperature and pressure at
these depths to find out how such bacteria can thrive. He says the extraordinary
pressure, around 1000 atmospheres, slows the replication of DNA. 鈥淚t means that
under extremely high pressures and low temperatures the generation time is very
long. The high pressure also leads to a much greater rate of mutation.鈥�
But while the microbiologists were over the moon about their finds, Fujioka
found the geology far less exciting. 鈥淢ost of this is sediment,鈥� he says,
indicating the flat, featureless environment recorded by Kaiko鈥檚 video camera.
鈥淚t鈥檚 mainly sands and clays which have been brought down from the upper slopes
of the trench鈥攖he kind of stuff we have seen a lot of in other
expeditions. There鈥檚 also a lot of detritus from the water above.鈥� In the dark
waters of the ocean bottom, where photosynthesis is impossible, animals make a
living by feeding off this detritus.
Before Kaiko left, it placed a marker on the ocean bed, announcing its
accomplishment. For the first time, there was a cheer in the control room. 鈥淲e
were all very pleased we had attained our goal,鈥� said Takagawa. 鈥淲e drank sake
and toasted the achievement with a `kampai鈥欌�擿cheers!鈥�.鈥�
Kaiko is now back in dry dock as the Yokosuka undertakes other exploratory
missions. JAMSTEC has commissioned a new mother ship, the Karei, specifically
for Kaiko, so that the deep-sea craft can devote more time to boldly going where
no marine craft has gone before. By next April, Kaiko should be exploring the
sea floor around Japan. And it may even evoke a greater spirit of romantic
adventure among its masters.
鈥淧erhaps if it were a manned craft and I was on board,鈥� says Fujioka, 鈥渢hen I
might be more excited.鈥�
