Earth’s Magnetic Field Is 3.5 Billion Years Old
- By Lisa Grossman
- March 5, 2010 |
- 2:29 pm |
- Categories: Earth Science
Evidence for the existence of Earth’s magnetic field has been pushed back about 250 million years, new research suggests. The field may therefore be old enough to have shielded some of the planet’s earliest life from the sun’s most harmful cosmic radiation.
Earth’s magnetic field was born by 3.45 billion years ago, a team including researchers from the University of Rochester in New York and the University of KwaZulu-Natal in South Africa report in the March 5 issue of Science.
That date falls during life’s earliest stages of development, between the period when the Earth was pummeled by interplanetary debris and when the atmosphere filled with oxygen. Several earlier studies had suggested that a magnetic field is a necessary shield against deadly solar radiation that can strip away a planet’s atmosphere, evaporate water and snuff out life on its surface.
“I think it’s a magnificent piece of work, a real landmark,” says geophysicist David Dunlop of the University of Toronto, who was not involved in the research. “It pushes the boundary back about as far back as you could reasonably expect to measure on Earth.”
The researchers measured the magnetic strength of certain rocks found in the Kaapvaal craton of South Africa, a geologic region known to date back more than 3 billion years.
Just finding old rocks wasn’t enough, though. “It’s a Goldilocks theory of finding rocks,” says John Tarduno of the University of Rochester, a coauthor of the new study. Iron minerals record the strength and direction of the magnetic field that was present during their formation. But when rocks are heated in subsequent geological processes, they can lose or overwrite that record.
“We had to find a rock that had just enough iron to record a magnetic signature, but not so much that it would be affected by later chemical changes,” Tarduno says.
The Greenstone Belt in South Africa had rocks that were just right: crystals of quartz less than two millimeters long with nanometer-sized bits of iron-containing magnetite embedded in them.
“Quartz is the perfect capsule,” Tarduno says. “It’s not affected by later events, but it has these [iron] inclusions in it.”
Tarduno and his colleagues had studied similar rocks in 2007 and found that a magnetic field half as strong as today’s was present 3.2 billion years ago. Using a specially designed magnetometer and improved lab techniques, the team detected a magnetic signal in 3.45-billion-year-old rocks that was between 50 and 70 percent the strength of the present-day field, Tarduno says.
“When we think about the origin of life, there are two threads to follow,” Tarduno says. “One obviously is water. But you also have to have a magnetic field, because that protects the atmosphere from erosion and the complete removal of water.” Mars may be dry today because it lost its magnetic field early on, he adds.
To determine if the early magnetic field was enough to hold back the rain of radiation, the team needed to know what the sun was doing. Tarduno and Eric Mamajek, an astronomer at the University of Rochester, used observations of young sunlike stars to infer how strong a solar wind the Earth was up against.
The young sun probably rotated more quickly than it does today, Tarduno says. This quick rotation powered a strong magnetic field, which heated the sun’s atmosphere and carried away mass and angular momentum in a strong solar wind of charged particles. The team calculated that the point where the Earth’s magnetic field cancels out the solar wind would be only about five Earth radii above the planet’s center, less than half of the 10.7 radii it is today.
The amount of radiation regularly reaching Earth from the sun 3.45 billion years ago would be comparable to what rains down on the planet during the most powerful solar storms today, Tarduno says. The aurora borealis, caused by solar wind particles accelerating along Earth’s magnetic field, would have been visible as far south as present-day New York City.
The study “can be used to guide our searches for other life-bearing planets” as well, says astronomer Moira Jardine of the University of St. Andrews in Scotland. Astronomers might want to focus more on older, less active stars or search for planets with their own magnetic fields, she says.
Despite the fact that no extrasolar planets with magnetic fields have ever been detected, Jardine and Tarduno remain optimistic. “It’s just another parameter we need to think about,” Tarduno says.
Images: 1) J. Tarduno, R. Cottrell. 2) NASA.
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That’s old. Got a question for the math space buffs. If the world were only 6 thousand years old (as some folks say). Given that light travels at 186 thousand miles per second. How big would the universe be if the furthest stars light was only 6 thousand years away? My guess - WAY TOO CROWDED. I suppose people could start disputing the speed of light too.
And she doesn’t look a day over 2 billion!
@GLacy, the universe would be 3.52 to the 16th power miles in radius and that is not crowded!
@GLacy
Or just that the light was created it the same time as the star emitting it.
I love all the Theories and evidences of the origins of the universe, it’s age and all that. I’m also intrigued at how many times in past history that the science books “Now Know” xyz, only to rewrite the books years later.
250 million years older? Yup, for about the next 10 to 50 years and they’ll rewrite about it again to fix todays’ “oops! We didn’t know about that….”
I love this stuff, can’t get enough
Gary Anderson
ala- @GanderCo
I love all the Theories and evidences of the origins of the universe, it’s age and all that. I’m also intrigued (at the historical fact) at how many times in past history that the science books write how they “Now Know” xyz, only to rewrite the books years later.
250 million years older? Yup, for about the next 10 to 50 years, and they’ll rewrite about it again to fix todays’ “oops! We didn’t know about this new evidence….”
I love this stuff, can’t get enough
Gary Anderson
ala- @GanderCo
“Despite the fact that no extrasolar planets with magnetic fields have ever been detected”
As far as I am aware, we don’t currently have the technology to detect a magnetic field around an extra solar planet. The magnetic fields around planets in our own solar system have almost exclusively been studied using probes such as voyager etc.
The only way that a magnetic field could be detected around an extra solar planet would be if an aurora could be detected/seen around its poles. Given that current telescopes cannot even provide a picture of an extra-solar planet, it would be impossible to detect a particular feature on a planet.
It’s a little disingenuous to say that none have been found, we just don’t have that information yet.
Who the f&#k thinks the world is 5K years old? Madness! WTF!? Question is retorted and retarded!
“I suppose people could start disputing the speed of light too”
Been done. Google speed of light creationist or Settlesfield. Quite easy to prove “scientifically”–just throw out any results you don’t like.
Proves how the rate of decay of radioactive elements changes over time too.
yeah, sure Gander–250 million out of 3.5 billion is about a 7% error. Surely the foundations of science have been shaken. Wadda maroon.
Why do the Jesus folks even both reading Wired, a decidedly scientific web site. Go to your freaking Jesus sites and leave the rational people alone!
The Planet Earth is not what we have been made to believe,only six thousand(6,000)years old.It(the Earth)is more than six trillion(6,000,000,000,000)years old,and it(the Earth)will be here for a long,long,time yet to come.According to my studies,the age of the Earth is around seventy-six trillion(76,000,000,000,000)years old.These years(seventy-six trillion)were divided into periods of six trillion years,beyond sixty-six trillion years,which would make the figure seventy-six trillion actually be seventy-eight trillion years.This is the age of the Earth.Or rather the oldest record that we have the Earth.No one knows exactly the age of the Universe,because there was no diameter measured through the darkness.In common words,there was no one there to record the movements,which brought about time.Ponder over these words……..
I would love to someday witness an aurora borealis!
This article seems to imply that the Earth’s magnetic field is a contributing factor to life’s formation and evolution on the planet. This is a well known fact nowadays. Nonetheless, it does coincide (and perhaps confirm) the timing of the appearance first life forms.
-PTS
http://www.parttimescholar.com
Out of curiousity and having no knowledge in the subject matter, how is a planetary magnetic field made in the first place? For example, why do we have one buy Mars does not?
I think there is no such thing as gravity it all pressured gases that keep everything bound to earth. gas pressure from space that formulate everything into pyramid molecules. at least that’s what this stuff is telling me Phoooot phooot phooooooot. where’s my roach container.
I don’t think Arnelle is claiming the Earth is 6,000 years old. Who ever he is pretending to talk would believe that, and then the rest of his comment is just gibberish.
But yes, I doubt there is anyone who is that evangelical that reads anything on this website.
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Arnelle, the universe is proven to be 13.5 billion (with a b) years old. This was done with multiple experiments using different methodology. One experiment, a spacecraft designed to map universal background radiation even created a picture of the universe at a few hundred million years old.
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the “earth is 6,000 years old” guys are trolls; calling them idiots just makes them feel like they’re significant–”Look! I got them stirred up! Someone noticed me!”
OTOH, Arnelle is simply unhinged. I do wonder how he/she measures a multitrillion year interval before time began. But I really don’t care.
Its more like, the world is 3000 years old. Considering we are in 2010, giving jesus teh benefit of the doubt, lets give the era named before him 1000 years of existence.
LOL
You DumbFaucks crackle me up. Sheesh, the world is 6000 years old. So what you are saying is that it took 2000 years for the dinosaurs to go extinct? Or do you not believe in the fossils that we find and then by using radio isotopes we can determine pretty much the time frame.
You should tell your god to have saved teh dinosaurs on his 7th day instead of resting. Well i guess he could have rested considering it takes a snap of his finger to save or destroy everything.
@martiannz - Actually, astronomers *can* measure magnetic fields from distant objects by measuring the polarization of light. We have been able to do this with many objects that are vast in size. However, I believe you are still correct; we cannot currently measure this in planets.
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@Glych - We’re not really 100% sure how Earth’s magnetic field was generated. We believe it has something to do with a dynamo generated by having a rotating, molten interior surrounding a solid iron core. Mars’ molten core is now solid, which probably contributed to its current lack of a strong magnetic field.
I do so love how people get stuck on 6000 years, last time I read the bible I did not see dates in there, just human guesses on that number. Like the same human guesses that beleive in the big bang (you know the theory that everything exploded out of nothing and defying the whole sum cant be greater than its parts theory) or the ever expanding universe (aka the world is flat theory just change ocean to space and ship to spaceship) Kinda wonder if you get to drink the “science” fiction koolaid in hell?
wow“““this is so beautiful….3.5 Billion Years Old…my god..how long earth can go on???prom dresses
@falconman: Given that the furthest known galaxy is 13 Billion light years away (if you pulled everything into the time frame of only 6 thousand years away) I would think that would “tighten” things up considerably. Just my guess.
All of the Young Earth Creation Scientists, repeat after me: “The Bible is not a science book.” Thank you. (By the way, I’m a Christian.)
@imaduck
Thank you, for your informative reply.
I wonder whether it would be possible to detect the magnetic field of an extra-solar planet by measuring changes in the polarisation of light coming from a star, and seeing if those fluctuations coincide with the orbit of the planet…..?
The “hot Jupiter” like planets should be good candidates for this, they are large, likely to have magnetic fields, close enough to influence their starts magnetic fields, and have a short enough “year” to produce results quickly.
Could that even work, or am I barking up the wrong tree?
I’ve just been reading about the NARVAL spectropolarimeter, and the work that has been done studying the light emitted by the star Vega.
Even if my suggestion theoretically has some merit, the sensitivity required is probably beyond the limits of current technology.