The immense rock sits just inside the edge of an unnamed crater in a region
called Terra Sabaea near the Martian equator. Because of its light colour, most
other researchers thought the rock might be made of calcium sulphate, formed by
the evaporation of water rich in the mineral.

But a team led by Michael Russell, a geologist at the Scottish Universities
Research and Reactor Centre in Glasgow, think the rock might be a
stromatolite— a carbonate mound built by microbes. In The
Journal of the Geological Society of London (vol 156, p 869), they say the
Martian rock resembles some unusual stromatolites that they recently discovered
in Turkey.

Stromatolites are formed when microorganisms—usually single-celled
cyanobacteria—extract calcium carbonate from water saturated with the
dissolved mineral. The bacteria pile up layer after layer of carbonate sediment,
creating mounds that have been likened to high-rise buildings.

Russell and his colleagues were visiting Lake Salda in western Turkey to
study some rare magnesium carbonate sand dunes, when they spotted some curious
small islands in the lake. samples from these islands showed they were rare
living stromatolites. Even more striking, says Russell, they are the only known
stromatolites built with magnesium, rather than calcium. “This is in fact the
really thrilling aspect,” he says.

The existence of magnesium-bearing stromatolites on Earth makes it possible
that the white rock formation on Mars could be a stromatolite. The rocks
surrounding the white rock and its crater look dark and magnesium-rich. There
could have been abundant magnesium in groundwater flowing into the crater for
any Martian microbes to build a mound.

David Wynn-Williams, a microbiologist at the British Antarctic Survey in
Cambridge, thinks Russell has a promising idea. “The trouble is, we don’t know
the composition of the `white rock’,” he says. Russell agrees, but says the NASA
Mars Global Surveyor is expected to do a spectral analysis of the site within
the next year, which should reveal whether or not the surface of the mound
contains large amounts of magnesium carbonate. A definitive answer will require
investigation on the Martian surface, however.

Stromatolites typically grow in distinctive layers, with alternating fine and
coarse bands of sediment. Russell says that although fossils of the tiny
microbes themselves would be unlikely to survive the harsh weathering conditions
on the surface of Mars, the distinctive banding should still be discernible in
the white rock, and could be easily recognised by a rover. If a future rover
mission finds the banding, Russell feels it will be a clear sign that life once
had a hold on Mars.

Given Neanderthals’ wide, heavy bones, most anthropologists had assumed that
their lives were dominated by brute force rather than wits. The popular theory
is that they were supplanted by lithe-limbed hominids who relied on subtle, less
physically demanding behaviours conjured up in their more powerful brains.

But perhaps not, says Christopher Ruff, a physical anthropologist at Johns
Hopkins School of Medicine in Baltimore. He has analysed the skeletons of
various members of the genus Homo spanning the last 2 million years,
employing techniques normally used to calculate strengths of beams and pillars
in buildings.

When the body mass that the bones had to support is taken into account, says
Ruff, there are only slight differences between the robustness of Neanderthal
bones and those of other hominids living around the same time. This suggests
that behavioural differences between Neanderthals and the other hominids were
smaller than many researchers suspected. “What we have evidence for here is for
gradual changes in behaviour that proceeded across the entire Pleistocene,” says
Ruff.

Ruff thinks that the Neanderthals’ stockier bodies may simply have been an
adaptation to living in a cold climate.

Many marine animals produce blue light from organs called photophores. They
can see the light they emit, but cannot see red light. Three species of deep-sea
fish are exceptions to this rule, emitting and seeing both blue and red light.
Two of these have visual pigments that are sensitive to unusually long
wavelengths in their retinas, enabling them to see the red light. This provides
them with a private wavelength for seeking out prey and mates
(This Week, 4 October 1997, p 7).

But the third species of red-seeing fish, the dragon fish Malecosteus niger,
does not have a red-sensitive pigment in its retina that it uses for vision
directly. Instead, Ron Douglas of City University in London and Julian Partridge
of the University of Bristol found that its retina contains a derivative of
chlorophyll which absorbs red light and somehow stimulates the pigments for
seeing blue light (Nature, vol 393, p 423). Douglas says this is “a completely
new form of vision”.

But where does the chlorophyll come from? “There’s no known animal that can
synthesise chlorophyll,” says Douglas. And with such threatening teeth, the fish
is no vegetarian. But in autopsies on M. niger, Tracy Sutton of the University
of South Florida in St Petersburg has discovered that the fish’s stomachs
contain tiny crustaceans called copepods. These copepods eat smaller copepods,
which in turn dine on phytoplankton containing chlorophyll. But how the fish
incorporates the chlorophyll into its retina is “still kind of an enigma”,
Sutton says.

For several years, dead otters have been washing up on the central
Californian coast, killed by parasites and other diseases. Kurunthachalam Kannan
of Michigan State University in East Lansing has carried out postmortems on 35
of the corpses and found that many had high levels of tributyl tin (TBT) in
their livers, up to 10 parts per million (Environmental Science and Technology,
vol 32, p 1169). Kannan says that other studies suggest just 1 ppm can kill
cultured fish liver cells.

Tributyl tin was added to marine paint to keep boat hulls clear of barnacles
and slime, but the US banned it from any vessel under 25 metres in 1989 after it
was found to be a potential immunosuppressant. Kannan and his colleagues say
that in the cool waters off central California, TBT should have a half-life of
about 10 years, so concentrations in marine sediments should have dropped since
the ban, and thus the bottom-feeding shellfish that otters eat should be
accumulating less of it. But judging by the high ratio of TBT to its breakdown
products in the otters’ livers, says Kannan, it must somehow still be in the
environment. “The animals were exposed to TBT very recently,” he claims.

Not everyone is convinced that TBT is killing the otters, however. Mark
Stephenson of the California Department of Fish and Game says that studies have
shown TBT does not travel far from harbours—which most otters shun.
“There’s something going on with the otters, but I’d be surprised if it was
TBT,” he says.

The fall of a host of civilisations in the Eastern Mediterranean at the end
of the Bronze Age has often been blamed on seafaring warriors who ransacked the
region around 1200 BC. But Amos Nur of Stanford University in California found
that skeletons of people buried in collapsed buildings had turned up in
excavations at about a dozen sites.

Suspecting earthquake damage, Nur compared the locations of 47 ancient cities
that were destroyed with maps of earthquake epicentres from the past 80 years.
Almost all the cities were in areas that today suffer the most intense seismic
shaking, suggesting that violent quakes could have been to blame.

A complicated junction of tectonic plates, with Africa diving under Europe
and some microplates caught in between, has created a maze of faults that Nur
believes causes periods of intense earthquake storms roughly every 400 years.
“During those storms, all the faults get activated,” says Nur.

In the middle of this century there was a thirty-year earthquake storm along
the North Anatolian Fault in northern Turkey, with magnitudes often reaching
between 7.0 and 7.5 on the Richter Scale. Nur told the AGU meeting that such
storms were common, with examples in the 8th and 15th centuries. The Romans
recorded a cluster in the 4th century.

Nur suspects that earthquake storms might be typical for complicated fault
patterns elsewhere, such as in the western Caribbean. If so, quake storms may
have destroyed civilisations in the Americas. “We are looking now at the
possibility that the Mayas collapsed because of earthquakes.”

THE quest for clean, smog-free air is today pursued with almost religious
zeal in many Western cities. In the US especially, laws on less-polluting fuels
and clean-engine technologies have ensured that several places are
experiencing their cleanest air for years.

But progress in urban air quality has come at a price, and in some US states
it is the groundwater that is picking up the tab. In 1990, the US Clean Air Act
obliged areas with poor air quality to add chemicals called oxygenates to their
petrol to increase its oxygen content and improve combustion, thereby reducing
emissions. However, the most commonly used oxygenate, methyl tertiary
-butyl ether (MTBE), has leaked into groundwater supplies from underground
petrol storage tanks at tens of thousands of sites across the US and
contaminated drinking water in California. It could become one of the US’s most
serious groundwater pollution crises for years.

MTBE tastes and smells like turpentine and because of this makes water
undrinkable in concentrations as low as a few tens of parts per billion. But
there are also serious concerns over its health effects (“Are Oxyfuels Good For
Us?”, żěè¶ĚĘÓƵ, 15 July 1995, p 24). Some scientists claim the
chemical causes cancer in animals, and the US Environmental Protection Agency
(EPA) has classified it as a potential carcinogen. Several pressure groups are
calling for MTBE to be banned, citing anecdotal evidence of breathing
difficulties, headaches and dizziness due to high concentrations of the chemical
in the air at petrol pumps.

Drinking it or breathing it in are not the only ways people can ingest MTBE.
Clifford Weisel, a researcher at the Environmental and Occupational Health
Sciences Institute in New Brunswick, New Jersey, says that based on similar
compounds he has worked with, MTBE can probably penetrate people’s skin during
washing. It could then accumulate in fatty tissues.

What sets the chemical apart as a contaminant is its mobility. Paul Squillace
of the US Geological Survey (USGS) says that it is tens of times more
water-soluble than any other constituent of petrol. It also has little affinity
for soil—once in water, it tends to stay there. So there is nothing to
slow its passage through the ground from leaking petrol tank to aquifer. Indeed,
it moves through the ground at virtually the same rate as the water in which it
dissolves. MTBE is also highly resistant to degradation. It will break down in
sunlight, but hardly at all in soil or groundwater. No one knows how long it
will persist if it is not cleaned up.

Thus any MTBE that leaks into the ground can pollute far larger areas than
other constituents of petrol. Anne Happel, who is studying the biodegradation of
MTBE at the Lawrence Livermore National Laboratory in California, says several
studies suggest that over 9000 petrol storage tanks in California alone have
leaked the chemical into groundwater.

A survey of eight urban areas across the US by the USGS in 1993 and 1994
found that out of 60 volatile organic compounds tested for in groundwater, MTBE
was the second most common after chloroform. If anything, its use has increased
since then. Christine Hawk, an analyst with the EPA, says that just over 30 per
cent of petrol in the US contains oxygenates and of that, 84 per cent contains
MTBE. This means that more than 25 per cent of petrol in the US contains between
11 and 15 per cent MTBE. “Even areas that don’t use the reformulated gasoline
still use MTBE as an octane enhancer, just at lower concentrations,” adds
Hawk.

Oxygenates are not used as extensively in Europe as in the US, but draft
European Union regulations on fuel quality that are currently under negotiation
would change that. Mario Sposini of the Milan-based company Ecofuel, which was
the first in the world to manufacture MTBE, says the new rules would make
less-polluting fuel mandatory, meaning that petrol might have to consist of up
to 15 per cent oxygenates. He adds that contamination should be less of a
problem than in the US because double-walled petrol tanks are common in
Europe.

MTBE contamination from petrol tanks is worst in California. In late 1995,
authorities in the city of Santa Monica detected the chemical in wells that
supplied the city with drinking water. In June the following year they were
forced to shut down some of the wells, and the city eventually lost 71 per cent
of its local water supply—about half its total water consumption.
According to Rey Rodriguez, utilities engineer for Santa Monica, the city now
has to buy 82 per cent of its water from outside sources at a cost of
$3.5 million a year.

Santa Monica is an extreme case, but MTBE has been found in an increasing
number of places in California since 1996, when the state made it compulsory for
all petrol to contain oxygenates. The chemical has turned up in lakes and
reservoirs, deposited by boat engines or carried there in surface runoff. Even
Lake Tahoe, high in the Sierra Nevada, is affected.

Because MTBE has such a strong affinity for water, it is harder and up to
twice as expensive to clean up as petrol that is free of it. There is an entire
industry in the US dedicated to removing petrol spills from soil and water, but
most of the technologies were developed before MTBE was introduced in large
quantities. żěè¶ĚĘÓƵs are looking for bacteria to add to contaminated water to
break down MTBE, but some of its daughter products—such as
tertiary-butyl alcohol—are also toxic, and any treatment would have
to degrade it completely.

In spite of the potential dangers of MTBE and extent of contamination, there
are many who oppose an outright ban— including the government. Lori
Stewart of the EPA says: “If you look at it on a nationwide basis, we’ve had
very little actual drinking water contamination from MTBE.” David Fogarty of the
Western States Petroleum Association points out that although there are other
oxygenates that could be used instead of MTBE, they all have drawbacks. “Ethanol
is simply not available in the quantities that are required in the California
market. You’d have to double the supply, and it’s a known carcinogen and
reproductive toxin.” Janet Hathaway, a senior attorney with the Natural
Resources Defense Council in San Francisco, says that because MTBE appears to be
less carcinogenic than benzene, which MTBE partially replaces in petrol, it is
actually reducing the cancer hazard.

A nationwide project launched by the EPA to upgrade old, single-walled
underground storage tanks or replace them with double-walled ones by the end of
1998 should stop many of the leaks. But that will not solve the problem of the
contamination that has already taken place. Meanwhile, MTBE could yet be banned
because of pressure from the industry that produces it.

Up until recently, oil companies have unanimously supported its use. But in
October, Tosco, the largest independent oil refiner in the US, wrote to the
California Air Resources Board asking it to “take decisive action immediately to
begin to move away from MTBE”. Tosco warned that extensive contamination would
result in huge costs to restore the state’s drinking supplies.

Campaigners hope that Tosco’s surprise move may mark the beginning of the end
for MTBE. But with no obvious alternatives, American cities would have to choose
between smog-free air or safe water. The quest for both remains as elusive as
ever.

According to Dave Sandison at Sandia, most organic materials naturally
fluoresce, but so faintly that the glow is swamped by ambient light. But for any
substance there is a wavelength of light that will make it fluoresce strongly,
and at a longer wavelength than the light that triggers it.

The Sandia detector will exploit this phenomenon by using an adjustable light
source that emits powerful bursts of light designed to trigger strong
fluorescence only in the material being sought. The person wielding the detector
will wear goggles that filter out the triggering wavelengths but not the
fluorescence they produce.

Even when the fluorescence is bright enough to be seen, an investigator still
has to tell it apart from surrounding objects lit by ambient light. For this,
the researchers rely on an effect called heterodyning, which makes the evidence
appear to flash.

Heterodyning works this way. The light source will rapidly switch on and off,
while the goggles will have a shutter that opens and shuts at a slightly
different rate. According to Colin Smithpeter of Sandia, the shuttering will be
too fast to be detected by the eye, so most of the view will appear perfectly
normal. But the fluorescence will be visible only when the light and the shutter
of the goggles are in sync. This will happen just a few times per second, so the
evidence will appear to flash.

Police searching for evidence already use lights, goggles, powders and dyes,
but most of these only work in the dark, which is a problem outdoors.

The police department at Albuquerque, New Mexico, will test the new system.
Ann Talbot, the department’s crime laboratory director, says: “It will
definitely make a difference in our work, if it works as they’re hoping.”

Tiltmeters of various simple designs have long been used to study volcanoes
on land. But these designs cannot be used on the seabed. The new tiltmeter has
two fluid reservoirs, one filled with ethylene glycol, the other with
isopropanol. These sit side-by-side on the ends of the branches of an elongated
U-shaped arrangement. Some 100 metres of copper alloy tubing runs out of each
reservoir and connects to a single sensor, which forms the bottom of the U. The
sensor measures pressure differences between the two fluids. Because the
reservoirs are next to each other, fluctuations in the local density of the
surrounding seawater should not affect the findings. Using two fluids also
filters out noise from temperature variations over time.

The results of a test on the Juan de Fuca Ridge in the Pacific, published in
the Journal of Geophysical Research, vol 102, indicate that the
tiltmeter can detect changes caused by a swelling magma chamber several days
ahead of an eruption, says Gregory Anderson, a student on the project.

But David Clague, director of research and development at the Monterey Bay
Aquarium Research Institute in Moss Landing, California, says tiltmeter data is
limited. “You don’t actually know whether the ground to the left went down or
the ground to the right went up,” he says. “All you know is that the ground
łŮľ±±ôłŮ±đ»ĺ.”

“You need to have more than one type of instrument in the area,”agrees
Anderson. He thinks the tiltmeter should be used in conjunction with instruments
such as seismographs.

TOXIC leftovers from illegal drugs labs that manufacture methamphetamine have
become a multimillion dollar headache for California, and the problem is
spreading to other parts of the US.

Hazardous materials specialists in California estimate that cleaning
abandoned labs will cost $7.65 million this year, nearly 85 per cent of
the state’s emergency cleanup budget. “It’s a booming business for us,
unfortunately,” says Don Plain of the California Environmental Protection Agency
in Sacramento.

Methamphetamine manufacture usually begins with a cold remedy—such as
ephedrine or pseudoephedrine—or a compound with a similar chemical
structure. The reagents used to transform these raw materials to methamphetamine
are often highly toxic, flammable, explosive or carcinogenic. The production of
1 kilogram of methamphetamine generates 7 kilograms of leftovers including
hydriotic acid, red phosphorus, benzene, freon, hydrogen chloride gas, ethyl
ether and sodium hydroxide.

“The common scenario is you go in there and you can’t believe they haven’t
blown themselves up,” says Donn Zuroski of the Office of Emergency Response of
the federal government’s Environmental Protection Agency in San Francisco, which
is called in whenever groundwater is contaminated. “There are a lot of dangerous
and toxic chemicals stored haphazardly.”

Plain says the fumes in one house were so strong that paint on the walls
liquefied. Sometimes buildings have to be demolished. Although the problem is
particularly acute in California, where cleanup teams are being called out twice
as often as two years ago, Zuroski says that problems with methamphetamine labs
are rising all across the US, as illicit consumption of the drug increases.

OFF the west coast of North America, a vast triangle of warm water has lured
tropical fish hundreds of kilometres northwards. El Niño, the disruption
of ocean currents now gripping the Pacific, has been held to blame. But this is
one climate anomaly that can’t be laid at El Niño’s door.

The triangle of warm water stretches from British Columbia in Canada to Baja
California in Mexico and out to Hawaii. In some places, the sea surface is 6
°C above normal for the time of year.

In an El Niño, trade winds that normally blow east to west slacken,
allowing warm surface waters to pool in the eastern Pacific. But Tom Murphree, a
climate physicist at the US Naval Postgraduate School in Monterey, California,
says that the triangle of water has been unusually warm for over a year, and
really started warming in earnest in April, before El Niño could have had
an effect.

Murphree says sea surface temperatures in the region are normally controlled
by a high-pressure system that settles off the coast of northern California,
pulling in wind and cool water from the north. This year, that high was much
weaker and smaller than usual, he says, and this led to warmer water flowing
into the area.

Huug van den Dool of the Climate Prediction Center in Washington DC, agrees.
“It’s sort of a coincidence that we have had all this warm water,” he says.