On the horizon: news from the frontiers of science

Astronomers spot hidden galaxies

Astronomers at the European Southern Observatory's Very Large Telescope (VLT) say they have added a new arrow to the quiver of galaxy hunters – an ability to study galaxies that until now could only be detected by their effect on light passing through them.

The background light comes from quasars, the brightest objects in the universe. These are found at distances of up to 13 billion light-years away. Researchers know that "hidden" galaxies exist along quasars' lines of sight. They can tell because the galaxies absorb telltale wavelengths from the spectrum in the light from the quasars behind them. But dimmed by their enormous distances – some 6 billion light-years away, these galaxies vanish into the quasars' glare.

Now, a European and Australian team has used a new detector on the VLT that can "untangle" the galaxy's light from a quasar's. The approach yields enough detail that researchers can measure many of the galaxy's properties.

Out of 20 patches of sky affected by quasars that display the telltale "dips" in their spectra, the team found 14 of these once-hidden galaxies. Those galaxies are forming stars at prodigious rates, the team says, and may open a window on galaxy formation during the earliest stages of the universe.

Does your tap water taste muddy?

Turn a spade in the garden on a summer day, and the smell of moist, fertile soil hits you immediately.

Now scientists at Brown University in Rhode Island say they have unraveled the chemistry behind that odor.

For more than 100 years, scientists have known that soil bacteria, as well as blue-green algae in lakes or ponds, produce a compound called geosmin. It's responsible for the smell of soil – and for an unpleasant, earthy taste in some tap water as well.

Sifting though soil bacteria, the team from Brown found a gene that carries the biological blueprint for a protein that makes geosmin. By understanding how geosmin is made, the researchers say they might be able to find a way to help microbiologists at water-treatment plants remove the muddy taste that affects tap water in some areas. The team's results appear in the current issue of journal Nature Chemical Biology.

Scientists map mercury's spread

Efforts to impose tough controls on airborne mercury pollution have long been contentious. Mercury falls to the ground, gets worked over by bacteria, then moves up the food chain, ultimately to be ingested by unwary humans. If stiff controls are enacted, however, it's quite likely that mercury levels in fish will drop fairly quickly – in a matter of years, rather than decades or longer.

That's the conclusion scientists draw from experiments they are conducting on a small research lake and its watershed in Ontario. The researchers added mercury to uplands and wetlands surrounding the lake, once a year for three years. During that period, they also added mercury once every two weeks to the lake when it was ice-free. Each of the three main watershed zones received a form of mercury with a unique chemical tag to identify its source once it reached fish in the lake. The amount of mercury they added simulated mercury pollution-levels from airborne sources found in many parts of North America. The goal was to track the mercury's movement through the three zones to see which of them had the largest effect on fish.

Over the first three years of this study, virtually all of the spike in mercury contamination found in the lake's fish during that period came from mercury deposited directly into the lake. Less than 1 percent came from the surrounding watershed.

As a result, scientists conclude that sharp reductions in mercury emissions are likely to lead to quick, significant reductions in mercury levels in the food chain. But it will take longer for the entire system to cleanse itself, because the compound moves slowly through the watershed and into the lake. The results appear in the current issue of the Proceedings of the National Academy of Sciences.