'Magnetic' Discovery May Reveal Why Earth
Supports Life and Mars Doesn't
by Charles Q. Choi, Live Science Contributor | July 30, 2015 04:33pm ET
An illustration of how Earth's magnetic field
protects the planet from solar radiation.
Earth's magnetic field, which protects the planet from harmful blasts of solar radiation, is much
older than scientists had previously thought, researchers say. In fact, this invisible, protective
shield likely existed shortly after the planet formed — a finding that could shed light on why
Earth is habitable and Mars is not.
Without Earth's magnetic field, solar winds — streams of electrically charged particles that flow
from the sun — would strip away the planet's atmosphere and oceans. As such, Earth's magnetic
field helped to make life on the planet possible, researchers have said.
The magnetic field is generated by swirling liquid metal in Earth's outer core, and this
"geodynamo" requires the release of heat from the planet to drive its churning. Nowadays, this
heat flow is aided by plate tectonics — the movement of the plates of rock that make up the
planet's exterior — which efficiently lets heat transfer from Earth's interior to its surface. [50
Amazing Facts About Planet Earth]
Given the importance of Earth's magnetic field, scientists want to pinpoint when it first
developed, which could, in turn, provide clues about how the planet has been able to remain
habitable and when plate tectonics began. However, when, exactly, plate tectonics originated is
hotly debated, and some researchers argue that the early Earth lacked a magnetic field.
Since 2010, the best estimate of the age of Earth's magnetic field was 3.45 billion years. In
comparison, Earth is about 4.6 billion years old.
Now, scientists have found that Earth's magnetic field could be up to 4.2 billion years old —
about 750 million years older than had been previously thought.
The researchers investigated magnetically sensitive minerals such as magnetite, a naturally
occurring cousin of rust. As molten rock cools, magnetite within it becomes literally set in stone,
pointing to the location of Earth's magnetic poles at the moment it froze. As a result, the oldest
samples of magnetite can reveal the direction and intensity of Earth's magnetic field at the
earliest parts of Earth's history, the researchers said.
The scientists analyzed magnetite samples trapped in tiny, ancient zircon crystals that were
collected from the Jack Hills in Western Australia. To detect the magnetic fields, the scientists
had to have a special magnetic sensor built that was 10 times more sensitive than other
instruments used to make these kinds of measurements.
Isolating the zircons from the surrounding rock was challenging. "Typically, we separate zircons
out using high magnetic fields, but we couldn't do that here, since it would destroy what
information they had," said John Tarduno, a geophysicist at the University of Rochester in New
York and lead author of the new study detailing the findings. "So we had to separate thousands
of zircons out by hand, cleaning them in mild acids, which took a huge amount of time,"
Tarduno told Live Science.
Then, to get reliable measurements, the researchers had to make sure the samples they analyzed
never got hot enough after they formed to allow the magnetic information recorded within to
reset. The researchers found that the minerals were pointed in a variety of magnetic directions,
which suggested the samples were pristine.
"[I]f the magnetic information in the zircons had been erased and re-recorded, the magnetic
directions would have all been identical," Tarduno said in a statement.
The intensity of the magnetic fields that the samples recorded suggests the presence of an ancient
geodynamo, the researchers said.
These findings likely indicate that Earth had a magnetic field, and plate tectonics, since very
early in its history.
"It's surprising, because some of the models of the ancient Earth suggest that a magnetic field or
plate tectonics could not have occurred that early," Tarduno said. "Those models need to be
rethought to include potential ways of cooling Earth's interior early on."
This ancient magnetic field could be a key reason Earth is still habitable and Mars was unable to
sustain life, as far as we currently know.
"The oldest previously known magnetic field from a terrestrial planet was on Mars, which was
older than 4 billion years old," Tarduno said. "But then, sometime after 4 billion years ago, it
died off. If you compare the evolution of Earth and Mars, Mars had a more dense atmosphere,
and water, but it probably lost both to erosion from the solar wind because it didn't have a
magnetic field to protect them, whereas Earth always appeared to have had a strong magnetic
shield."
Earth's Magnetic Field Is Weakening 10
Times Faster Now
by Kelly Dickerson, Staff Writer | July 08, 2014 11:29am ET
Changes measured by the Swarm satellite over the past 6
months shows that Earth's magnetic field is changing. Shades of red
show areas where it is strengthening, and shades of blue show areas
that are weakening.
Credit: ESA/DTU
View full size image
Earth's magnetic field, which protects the planet from huge blasts of deadly solar radiation, has
been weakening over the past six months, according to data collected by a European Space
Agency (ESA) satellite array called Swarm.
The biggest weak spots in the magnetic field — which extends 370,000 miles (600,000
kilometers) above the planet's surface — have sprung up over the Western Hemisphere, while
the field has strengthened over areas like the southern Indian Ocean, according to the
magnetometers onboard the Swarm satellites — three separate satellites floating in tandem.
The scientists who conducted the study are still unsure why the magnetic field is weakening, but
one likely reason is that Earth's magnetic poles are getting ready to flip, said Rune Floberghagen,
the ESA's Swarm mission manager. In fact, the data suggest magnetic north is moving toward
Siberia.
"Such a flip is not instantaneous, but would take many hundred if not a few thousand years,"
Floberghagen told Live Science. "They have happened many times in the past."[50 Amazing
Facts About Planet Earth]
Scientists already know that magnetic north shifts. Once every few hundred thousand years the
magnetic poles flip so that a compass would point south instead of north. While changes in
magnetic field strength are part of this normal flipping cycle, data from Swarm have shown the
field is starting to weaken faster than in the past. Previously, researchers estimated the field was
weakening about 5 percent per century, but the new data revealed the field is actually weakening
at 5 percent per decade, or 10 times faster than thought. As such, rather than the full flip
occurring in about 2,000 years, as was predicted, the new data suggest it could happen sooner.
Floberghagen hopes that more data from Swarm will shed light on why the field is weakening
faster now.
Still, there is no evidence that a weakened magnetic field would result in a doomsday for Earth.
During past polarity flips there were no mass extinctions or evidence of radiation damage.
Researchers think power grids and communication systems would be most at risk.
Earth's magnetic field acts like a giant invisible bubble that shields the planet from the dangerous
cosmic radiation spewing from the sun in the form of solar winds. The field exists because Earth
has a giant ball of iron at its core surrounded by an outer layer of molten metal. Changes in the
core's temperature and Earth's rotation boil and swirl the liquid metal around in the outer core,
creating magnetic field lines.
The movement of the molten metal is why some areas of the magnetic field strengthen while
others weaken, Florberghagen said. When the boiling in one area of the outer core slows down,
fewer currents of charged particles are released, and the magnetic field over the surface weakens.
"The flow of the liquid outer core almost pulls the magnetic field around with it," Floberghagen
said. "So, a field weakening over the American continent would mean that the flow in the outer
core below America is slowing down."
The Swarm satellites not only pick up signals coming from the Earth's magnetic field, but also
from its core, mantle, crust and oceans. Scientists at the ESA hope to use the data to make
navigation systems that rely on the magnetic field, such as aircraft instruments, more accurate,
improve earthquake predictions and pinpoint areas below the planet's surface that are rich in
natural resources. Scientists think fluctuations in the magnetic field could help identify where
continental plates are shifting and help predict earthquakes.
Read each article. Answer the following question in COMPLETE SENTENCES.
Article 1 – Magnetic Discovery May Reveal Why Earth Supports Life and Mars Doesn’t
How does Magnetite form?
How can scientists use magnetite to determine the age of the Earth’s magnetic field?
What type of crystals did the magnetite form in? What were the requirements for them to be used to
know the information they held was accurate?
What happens to the surface of a planet if there is not magnetic field to protect it?
What created the Earth’s Magnetic field?
How old is the Earth?
How old is the Earth’s Magnetic Field? How old did scientists believe the Earth’s magnetic field was
BEFORE finding this information?
Article 2 – Earth’s Magnetic Field is Weakening 10 times Faster Now
How far does Earth’s Magnetic Field extend?
What causes some areas of Earth’s magnetic field to weaken/strengthen?
Would there be long-term effects of a polarity flip? What has happened in the past?
How long does a polarity flip take?
How fast is the Earth’s Magnetic field weakening (compared to the past)?
The Magnetic North pole is now moving towards __________________.
Write a paragraph (At LEAST 8 sentences) describing whether you think the Polarity of the Earth will flip,
when you think it will flip, and what will happen to the Earth if it flips or if the Magnetic Field disappears.
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________