Two recent deep-sea explorations have paved the way for our understanding of our planet's extreme environments and what life forms might be like on other planets and moons within our Solar System and beyond.
In an engineering triumph that makes Captain Nemo look like a fat kind with water wings, the Nereus (rhymes with "serious") has plumbed the very depths of the ocean. The Nereus, named after a mythical Greek god with a fish-tail and a man's torso, dove to 10,902 meters (6.8 miles) on May 31 in the
Challenger Deep in the Mariana Trench in the western Pacific Ocean. The über-aquatic
probe has recovered rocks from the very bottom of the trench,
proving that there is absolutely nowhere we can't get if we set our
minds to it.
"The team is pleased that Nereus has been successful in reaching the very bottom of the ocean to return imagery and samples from such a hostile world," reported Andy Bowen, project manager and principal developer of Nereus at the Woods Hole Oceanographic Institution (WHOI). "With a robot like Nereus we can now explore anywhere in the ocean. The trenches are virtually unexplored, and Nereus will enable new discoveries there. Nereus marks the start of a new era in ocean exploration."
The Mariana Trench forms the boundary between two tectonic plates, where the Pacific Plate is subducted beneath the small Mariana Plate. It is part of the Pacific Ring of Fire, a 40,000-kilometer area where most of the world's volcanic eruptions and earthquakes occur.
Plumbing the ultimate depths of the ocean is a major engineering challenge, with the Nereus
probe specially constructed to survive one thousand atmospheres of
pressure. That's enough to crush any other human construction, even
submarines which are - when you think about it - ultra solid metal
cylinders propped up with more metal. The Nereus
is a three-ton robot containing specially-designed ceramic flotation
spheres and pressure-adapted cellphone-style lithium-ion batteries.
The
main problem is one you wouldn't even think of - the control cable.
Ten kilometers of cable simply doesn't work, with even the strongest
chain snapping under its own weight at such scales, so the engineers
instead used an ultralight fibreoptic cable - the width of a human hair but seven miles long - to communicate with their exploring robot.
The aquatronics
didn't just adventure beyond the bounds of human travel, it brought
some samples back. Chunks of sediment and rock samples were recovered
from this unique environment, where the landscape is affected by
exposure to the Earth's mantle, promise priceless information about
plate tectonics and the construction of this rock ball we live on.
Future
underwater adventures will use a new hybrid control mode. The first
tests were entirely pilot-controlled, but the ocean is pretty big so
the Nereus is designed with an automatic
reconnaissance mode to survey swathes of subaqua territory, switching
over to human control when something interesting is observed. So at
least if it goes insane, it won't be able to hurt anyone but Aquaman.
One of the most fascinating examples of what future deep-sea exploration may reveal occurred on an earlier expedition off the coast of Peru. The expeditions' objective was to research tiny ancient microbes beneath the sea floor that influence the Earth's
long-term carbon cycle.
Distinct from life on the Earth's surface,
these microbes may account for one-tenth of the Earth's living biomass,
according to an interdisciplinary team of researchers who looked at
sediment samples from a variety of depths at the The Peruvian Margin,
but many of these minute creatures are living on a geologic timescale.
The team examined how the microbial world differs in the sub-sea floor
from that in the surface waters, with profound implications for our
understanding of possible lifeforms elsewhere in the Solar System.
"Our first study, back in 2006, made some estimates that the cells
could double every 100 to 2,000 years," said Jennifer F. Biddle, PhD. in biochemistry and former postdoctoral fellow in
geosciences, Penn State. "Now we have the first comprehensive look at
the genetic makeup of these microbes."
"The Peruvian Margin is one of the most active surface waters in the
world and lots of organic matter is continuously being deposited
there," says Christopher H. House, associate professor of geoscience.
The researchers used a metagenomic approach to determine the types
of microbes residing in the sediment 3 feet, 53 feet, 105 feet and 164
feet beneath the ocean floor. The use of the metagenomics, where bulk
samples of sediment are sequences without separation, allows
recognition of unknown organism and determination of the composition of
the ecosystem.
"The results show that this subsurface environment is the most
unique environment yet studied metagenomic approach known today," says
House. "The world does look very different below the sediment surface."
The researchers found that a large percentage of the microbes were
Archaea, single-celled organisms that look like bacteria but are
different on the metabolic and genetic levels. The percentage of
Archaea increases with depth so that at 164 feet below the sea floor,
perhaps 90 percent of the microbes are Archaea. The total number of
organisms decreases with depth, but there are lots of cells, perhaps as
many as 1,600 million cells in each cubic inch.
If the rest of the world is like the Peruvian Margin, then at least
one tenth and as much as a third of the Earth's biomass could be these
tiny microbes living in the dark mud. However, this population lives at
an unusual rate. Single-celled organisms usually consume food for
energy and then rather than grow larger, simply divide and reproduce
themselves. While the Bacteria Escherichia Coli, as an example, doubles
its numbers every 20 minutes, these Archaea double on the order of
hundreds or thousands of years and consume very little energy.
"In essence, these microbes are almost, practically dead by our
normal standards," says House. "They metabolize a little, but not much."
According to House, organisms metabolizing at such slow rates is
what we could expect to find in other areas of our solar system because
such environments have much less energy available than on Earth.
Perhaps, similar organisms may be in hydrothermal vents beneath the ice
of Europa — the second moon of Jupiter — or in subsurface aquifers of
Mars.
"We do not expect the microbes in other places to be these microbes
exactly," says House. "But, they could be living at a similar slow
rate."
Biddle notes that these microbes could survive major Earth impacts
by asteroids, so the subsea floor could be a refuge for life during
extinction events. Now this study shows they may be a reservoir of
novel genetic material as well. Her future research will focus on
understanding the lifestyle of the microbes.
"For example, how do they die?" asks Biddle. "It is a simple question that we cannot answer."
Posted by Casey Kazan.
Nereus Probe http://www.nsf.gov/news/news_summ.jsp?cntn_id=114913&govDel=USNSF_51
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