Biology

Would we exist if Earth's magnetic field hadn't collapsed 500m years ago?

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An artist's impression of the Ediacaran Period, a time when the Earth's magnetic field was at its weakest
University of Rochester illustration / Michael Osadciw
An artist's impression of the Ediacaran Period, a time when the Earth's magnetic field was at its weakest
University of Rochester illustration / Michael Osadciw
A fossil of Dickinsonia, a bizarre lifeform that lived during the Ediacaran Period
Shuhai Xiao, Virginia Tech

The Earth’s magnetic field is vital for life – without it, the Sun’s radiation would sterilize the planet. But a new study suggests we wouldn’t be here at all if that magnetic field hadn’t almost completely collapsed half a billion years ago.

A lot of factors had to come together just right for Earth to be habitable. Not only did the planet need to be exactly the right distance from the Sun, but it needed to be rocky, watery, contain the right ingredients for life, and of course, have a strong magnetic field that prevents dangerous radiation from the Sun and interstellar space from reaching the surface.

While it’s mostly stable, that magnetic field does fluctuate over time. In a new study, scientists from the University of Rochester identified its weakest point in Earth’s history – but surprisingly, it seems to have happened just before complex life exploded on the scene, rather than coincide with a mass extinction as you might expect.

Ancient minerals can preserve a record of the magnetic field’s strength at the time, thanks to magnetic particles in them. The Rochester researchers measured this magnetization in feldspar and pyroxene crystals, comparing samples from over 2 billion years ago to some from 591 million years ago. They found that the older samples recorded a magnetic field of similar strength to today’s, but the younger samples suggested that the magnetic field at that time was just 3% of its current strength – its weakest point we know about.

It seems that this weaker magnetic field lasted for at least 26 million years, before it started to regain strength. That’s right around the time the Earth’s inner core solidified and stabilized the magnetic field, according to the team’s previous work.

A weaker magnetic field means more cosmic radiation reaches deeper into Earth’s atmosphere, and if that happened today it would likely trigger a mass extinction event. But intriguingly, this historical low point may have helped the ancestor of all animals evolve.

A fossil of Dickinsonia, a bizarre lifeform that lived during the Ediacaran Period
Shuhai Xiao, Virginia Tech

The Ediacaran Period, which lasted from 635 to 539 million years ago, was a key stage in the evolution of life on Earth. This was when complex multicellular lifeforms first emerged, but they barely resemble life as we know it now – they looked like discs, tubes, fans, donuts, or just squishy “mud-filled bags.” In fact, scientists can’t really even figure out if these organisms were algae, fungi, or early versions of plants or animals.

Most of these weirdos seemed to die out by the following period, the Cambrian. But around the same time, there was a massive explosion in the diversity of lifeforms, with almost every modern branch on the evolutionary tree appearing in a relatively short space of time. One of the main triggers for that event is believed to be an increase in oxygen levels in the atmosphere – and according to the new study, we might have that weakened magnetic field to thank.

As mentioned, that dip let more radiation enter Earth’s atmosphere, which allowed more charged particles to strip away atoms like hydrogen. If enough of those are lost to space, then the oxygen atoms in the atmosphere build up, rather than reacting with the hydrogen to form water vapor. Over time, that increases levels of oxygen in the air, giving the burgeoning life a boost.

If the story is true, it goes to show the remarkable luck that advanced life was able to evolve at all. If the magnetic field hadn’t bounced back, Earth might have instead gone the way of Mars.

“If the extraordinarily weak field had remained after the Ediacaran, Earth might look very different from the water-rich planet it is today: water loss might have gradually dried Earth,” said John Tarduno, an author of the study.

The research was published in the journal Nature Communications Earth & Environment.

Source: University of Rochester

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13 comments
christopher
Always amuses me how some folks believe we'd have some chance of making contact with aliens, when it's abundantly clear that it's taken the randomness of the entirety of all space and time to create the conditions we needed to evolve from. The probability that could have happened *again* anyplace within our event horizon is absurd.
Brian M
@christopher - Yes the probability of it happening again is infinitesimally small, but the universe is infinitely large, so the probability of other intelligent life out there heads towards a probability of 1.

Although in practical terms you are right they might be so far away we might never meet them or even detect them!
But who knows where technology might takes us with quantum physics etc.
Andrew Charnley
The opposite argument is interesting and challenging, rather than amusing: Our galaxy, the Milky Way has about 100 billion stars – 100,000,000,000. By multiplying the number of stars in a typical galaxy (100 billion) by the number of galaxies in the universe, scientifically estimated at 2 trillion - this more than suggests there is approximately 200 billion trillion stars in the universe, that is 200 sextillion.

That’s 200,000,000,000,000,000,000,000 meaning the odds are more than favourable for their to be more than one planet like earth proving the opportunity for 'LIFE'. We might not like or appreciate what that life-form is but the odds are more for, than against.
Jose Gros-Aymerich
Yes, the Earth Magnetic Field sometimes reverses polarity, for a while, power of this Magnetic Field goes to zero.
This seems happening right now, an easy to watch consequence is 'Northern Lights', aurora, showing in lower latitudes, even at Equator.
Wait and see!
David F
Whatever the odds, "life finds a way."
lon4
There goes the idea of much life on Mars, since it has no magnetic field!
Sean Reynolds
If this were true then why does Venus (without a magnetic field like ours) still have an atmosphere that is roughly 92x the pressure of Earths?
Sean Reynolds
I guess what I'm trying to say is that life began in the ocean which would also be really effective at blocking the solar radiation. I'm just not buying the premiss. Life finds a way :)
Marty1954
God created the heavens and the earth, he called each step a day. I like to think of it as a “creative period”. I’m sure he knew what he was doing when he turned earth’s magnetic field down.

As for other earths? God’s creations are without number, so, I know that there are other earths out there. We just don’t know how many or how far away they are.
Karmudjun
I enjoy reading these "new" findings. When determining if life started (amino acid presence, ongoing life form lifecycles) on earth or on an asteroid, the scientific thinking goes along the lines of RNA/DNA development in a milieu rich for sustaining life - but with the right amount of irradiation to induce spontaneous RNA/DNA mutations for variety. In grade school, some five decades ago we decided that radiation must have varied on earth - or an Asteroid brought the building blocks to earth - or the combination. And we also believed God had some hand in it all. So the probabilities are enormous, not *absurd*.