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Reuters/Reuters - NASA
undated handout image shows an image of the earth taken from space.
REUTERS/NASA/JHandout
LONDON (Reuters) - The discovery by NASA rover
Curiosity of evidence that water once flowed on Mars - the most Earth-like
planet in the solar system - should intensify interest in what the future could
hold for mankind.
The only thing stopping Earth
having a lifeless environment like Mars is the magnetic field that shields us from deadly solar radiation and
helps some animals migrate, and it may be a lot more fragile and febrile than
one might think.
Scientists say earth's
magnetic field is weakening and could all but disappear in as little as 500
years as a precursor to flipping upside down.
It has happened before - the
geological record suggests the magnetic field has reversed every 250,000 years,
meaning that, with the last event 800,000 years ago, another would seem to be
overdue.
"Magnetic north has
migrated more than 1,500 kilometres over the past century," said Conall Mac Niocaill,
an earth scientist at Oxford University. "In the past 150 years, the
strength of the magnetic field has lessened by 10 percent, which could indicate
a reversal is on the cards."
While the effects are hard to
predict, the consequences may be enormous. The loss of the magnetic Mac Niocaill said Mars probably lost its magnetic field
3.5-4.0 billion years ago, based on observations that rocks in the planet's
southern hemisphere have magnetisation.
The northern half of Mars
looks younger because it has fewer impact craters, and has no magnetic
structure to speak of, so the field must have shut down before the rocks there
were formed, which would have been about 3.8 billion years ago.
"With the field dying
away, the solar wind was then able to strip the atmosphere away, and you would
also have an increase in the cosmic radiation making it to the surface,"
he said.
"Both of these things
would be bad news for any life that might have formed on the surface - either
wiping it out, or forcing it to migrate into the interior of the planet."
RIGHT HERE, RIGHT NOW
Earth's magnetic field has
always restored itself but, as it continues to shift and weaken, it will
present challenges - satellites could be more exposed to solar wind and the oil
industry uses readings from the field to guide drills.
In nature, animals which use
the field could be mightily confused - birds, bees, and some fish all use the
field for navigation. So do sea turtles whose long lives, which can easily
exceed a hundred years, means a single generation could feel the effects.
Birds may be able to cope
because studies have shown they have back-up systems that rely on stars and
landmarks, including roads and power lines, to find their way around.
The European Space Agency is
taking the issue seriously. In November, it plans to launch three satellites to
improve our fairly blurry understanding of the magnetosphere.
The project - Swarm - will
send two satellites into a 450 kilometre high polar orbit to measure changes in
the magnetic field, while a third satellite 530 kilometres high will look at
the influence of the sun.
field on
Mars billions of years ago put paid to life on the planet if there ever was
any, scientists say.
DESCENT INTO CHAOS
Scientists, who have
known for some time the magnetic field has a tendency to flip, have made
advances in recent years in understanding why and how it happens.
The field is
generated by convection currents that churn in the molten iron of the planet's
outer core. Other factors, such as ocean currents and magnetic rocks in the
earth's crust also contribute.
The Swarm mission
will pull all these elements together to improve computer models used to
predict how the magnetic field will move and how fast it could weaken.
Ciaran Beggan, a
geomagnetic specialist at the British Geological Survey in Edinburgh, said
studies have also refined our understanding of how the field reverses.
They have focused on
lava flows. When these cool and form crystals the atoms in iron-rich molten
rock align under the influence of the magnetic field, providing a geological
memory of the earth's field.
But that memory looks
different in various locations around the world, suggesting the reversal could
be a chaotic and fairly random process.
"Rather than
having strong north and south poles, you get lots of poles around the planet.
So, a compass would not do you much good," said Beggan.
While the whole
process takes 3,000-5,000 years, latest research suggests the descent into a
chaotic state could take as little as 500 years, although there are significant
holes in scientific understanding.
"Although
electricity grids and GPS systems would be more vulnerable, we are not really
sure how all the complex things that are linked together would react,"
Beggan said.
(Editing by Dan
Lalor)
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