3 December 2011| NewScientist | 5

Perhaps no longer. Phil Lester and colleagues at the Victoria University of Wellington say that alien ant colonies in 60 locations are collapsing on their own (Biology Letters, DOI: 10.1098/ rsbl20111014). Lester thinks low genetic diversity, which is associated with reduced disease resistance, is the most likely reason for the ant’s demise.

Lori Lach at the University of Western Australia, Perth, warns that other alien species won’t be so easily dealt with. “For thousands of other invasive species around the world we’ve seen no such collapse,” she says.

Some dark secretsDESPITE making up 80 per cent of the universe, dark matter is maddeningly elusive. Now it is giving up a few secrets – although not its full identity.

Dark matter provides the gravity that stops galaxies from flying apart, but interacts so weakly with ordinary matter that it is unclear what it is. Now two separate analyses of gamma rays in space, some of which formed in dark-matter collisions, give a clue. They suggest that if dark matter is made up of particles, as leading theories suggest, these must be at least 44 times as heavy as protons. “This is the strongest limit to the mass that we have so far,” says Savvas Koushiappas of Brown University in Providence, Rhode Island, part of one of the teams.

The studies, due to appear in Physical Review Letters, contradict three earlier findings that dark matter particles have less than a quarter of that mass, but are not the final word. For instance, Dan Hooper of Fermilab in Batavia, Illinois, who was behind one of those findings, says the new work assumes a certain decay path for dark matter but the particles could be lighter if the true path is different. “They’re ruling out certain kinds of particles, but they’re not ruling out mine.”

Nano killer futureFORGET antibiotics, let’s try nanoparticles. That’s according to DARPA, the US military’s research arm, which says that rather than spend money on new antibiotics, which only work until bacterial strains grow resistant, “readily adaptable nanotherapeutics” can fight infection instead.

The agency has called for proposals to find ways to use small interfering RNA (siRNA) to fight bacteria. These scraps of genetic code seek out their mirror image within cells, such as bacteria, and silence them. This

stops protein production and leads to cell death.

DARPA is seeking ideas for adaptable nanoparticles that can be “reprogrammed on the fly” by loading up specific siRNA to deal with outbreaks among troops.

As with GPS systems and the internet, this innovation might benefit the military initially, but eventually become a model for mainstream medication.

“The US military is seeking adaptable nanoparticles that can be reprogrammed on the fly to fight bacteria”

IT READS like a fairy tale from the brothers Grimm: a giant US state is planning a giant hydroelectric dam that could flood a tiny shrew out of its idyllic home.

Next month, Alaskan authorities will file plans in Washington DC for a 213-metre megadam on one of the country’s last remaining wild rivers: the Susitna (pictured below). If approved, it would be the country’s first hydroelectric megadam for 40 years, and its fifth tallest, just 8 metres shy of the Hoover dam.

In 1995, Daniel Beard, head of the US Bureau of Reclamation, the nation’s main constructor of dams, declared the US dam-building era over. He cited growing environmental concerns. Dozens of dams have

since been torn down to revive fisheries and reinstate river habitats. But after years in the environmental doghouse, large dams are being promoted as a source of low-carbon energy, and the 600-megawatt Susitna project looks like it could be the first to get the green light.

Opponents say the project is a $4.5 billion boondoggle, and the state should tap its abundant tidal, geothermal and wind power instead. But the icon for protest against it may turn out to be the country’s most secretive shrew. Weighing in at just 1.5 grams, Sorex yukonicus lives on a bank 10 kilometres downstream of the proposed site for the dam. Extensive searches have turned up just 38 individuals so far.

The giant dam and the tiny shrew

–May not be idyllic for long–

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Rover en route to Mars“I’m feeeeelin’ good,” tweeted NASA’s Mars rover Curiosity after its launch on Saturday. After a planned landing in August, it is set to search for signs of life. Meanwhile, Russian ground control have been unable to establish a link to their stalled Mars probe Phobos-Grunt.

Climatic ironyThe tiny, super-rich gulf state of Qatar will host UN climate negotiations COP 18 in 2012. Qatar has the world’s highest per capita carbon emissions. At more than 50 tonnes a head, emissions are seven times those of the UK and more than triple those of the US.

Eat less to save forests Growing demand for vegetable oil is destroying tropical forests by driving the expansion of oilseed plantations. If everyone in Europe and the US cut their daily consumption of the oil by 25 grams – equivalent to one large helping of fries – 70 per cent less forest would be lost (Biological Conservation, DOI: 10.1016/j.biocon.2011.10.029).

Land gone to seedWe have trashed a quarter of the Earth’s land surface, according to the first global survey of land resources, by the UN Food and Agriculture Organization, which blames the damage on unsustainable farming. Food production grew 150 per cent between 1961 and 2009 through intensive farming that damaged soil and depleted water supplies.

Killer “insane”Anders Breivik, the Norwegian gunman who killed 77 people, was insane when he committed the acts in July, says a psychiatric report. Norway’s state prosecutor says the report concludes that Breivik was “psychotic” during the attacks, and had paranoid schizophrenia. If the Oslo district court backs the report’s findings, Breivik may escape criminal accountability.

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