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.