Power Surges

The space weather report for Mercury: stormy, with a chance of power surges.

New data from the third and final flyby of the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft have revealed surprisingly intense electromagnetic storms in Mercury's magnetic "tail," part of the planet's magnetic field.

(Related: "Magnetic Twisters 'Dance' Across Mercury, Study Says.")

Such tails form when the solar wind—charged particles streaming from the sun—pushes on a planet's magnetic field. The deformed field flows around the planet in a windsock shape, like river water flowing around a rock.

All eight planets in the solar system except Mars and Venus have magnetic fields and tails, although Mercury's field is the smallest and weakest.

But during a September 29, 2009, flyby of the tiny planet, MESSENGER watched as Mercury's magnetic tail collected enormous amounts of energy from the solar wind.

In just 90 seconds, the tail increased magnetic field power by 200 percent during an event known as a magnetic substorm. The tail then snapped back to normal, dissipating the energy over the next minute and a half.

On Earth, a similar process—called tail loading—takes an hour and increases the magnetic field's energy by only about 10 percent.

"This is all very curious," said Jim Slavin, a solar physicist at NASA Goddard Spaceflight Center and lead author of a new paper describing the finding.

"We have very weak solar wind conditions, yet we're seeing more tail loading than what we see on Earth. What's going to happen when the [solar] wind conditions pick up?"

MESSENGER may have a chance to find out: The space probe will settle into a stable orbit around Mercury in 2011, just in time for a predicted peak in solar activity in 2012 or 2013.

Long odds of finding ET

The odds of successfully eavesdropping on the daily radio traffic of extraterrestrial life forms have been calculated by a pair of UK scientists to be astronomically small.

The calculation is presented in a paper accepted for publication in the International Journal of Astrobiology and appearing on the pre-press website arXiv.org.

Duncan Forgan, from the University of Edinburgh and Professor Bob Nichol from the Institute of Cosmology and Gravitation, used a computer modelling technique, called Monte Carlo Realisation, to simulate the growth and evolution of intelligent life in our galaxy.

They combined this with previous research showing the next-generation Square Kilometre Array (SKA) telescope will be able to pick up radio traffic from ET up to distances of 300 light years from Earth.

They calculated that the probability of picking up such transmissions as being extremely low - 1 in 10 million, to be precise.

Forgan and Nichol assume that ET will only "leak" radio signals for about 100 years of its civilisation.

They say humans have been leaking signals from TV and military radar for that length of time, but are now becoming "radio quiet" as signals move to lower power.

Gorillas learn to play fair by playing tag

There's more to an innocent game of tag than meets the eye. When gorillas play the playground favourite, it teaches them a valuable life lesson about unfairness, social boundaries and retaliation. That, at least, is the conclusion of the first study to observe the primates' reactions to inequity outside a controlled laboratory setting.

Young gorillas often engage in play fights that resemble what children do in a game of tag: one youngster will run up to another and hit it, then run away. The other gorilla then gives chase and hits the first one back (see video, above).

Marina Davila-Ross of the University of Portsmouth, UK, and colleagues studied video footage of six groups of gorillas in zoos. Twenty-one juveniles – both males and females – were observed chasing one another in a total of 86 games.

They found that the gorilla that did the hitting almost always moved to run away before its victim started moving. The researchers argue that this means the hitter is expecting retaliation and has therefore learned something about acceptable social behaviour.

It was a different story, however, when the gorillas played the game more gently, grabbing each other rather than hitting. Then the "grabber" was not the first to run – perhaps because the gorillas saw the gentler act as less aggressive. "Apes use play to explore the ramifications of unfair social situations," says Davila-Ross.

Heart of darkness could explain sun mysteries

IS DARK matter lurking at the centre of our bright sun? Yes, say two research groups who believe the elusive stuff is cooling the solar core.

The insight doesn't significantly affect the sun's overall temperature. Rather, a core chilled by dark matter would help explain the way heat is distributed and transported within the sun, a process that is poorly understood.

Dark matter doesn't interact with light and so is invisible. The only evidence for its existence is its gravitational effects on other objects, including galaxies. These effects suggest dark matter makes up about 80 per cent of the total mass of the universe.

The idea that it might lurk at the heart of the sun goes back to the 1980s, when astronomers found that the number of ghostly subatomic neutrinos leaving the sun was only about a third of what computer simulations suggested it should be. Dark matter could have explained the low yield because it would absorb energy, reducing the rate of the fusion reactions that produce neutrinos.

However, the problem was solved another way when it was found that neutrinos oscillate between three kinds, only one of which was being detected on Earth. As a result, the idea of solar dark matter was dropped.

Now it is being resurrected in the light of recent searches for dark matter, which have put limits on the mass of the particles that it is made of and shown that it interacts only very weakly with ordinary matter. These led Stephen West of Royal Holloway, University of London, and his colleagues to explore what would happen if particles that fell within these limits exist in the sun.

Their simulations show that gravity would pull such dark particles to the centre of the sun, where they would absorb heat. Some of these dark matter particles would then carry this heat from the core to the surface, decreasing the core temperature