You may have heard that Mars doesn’t have a magnetic field. But that’s not true!
Now, thanks to data from NASA’s MAVEN satellite,
researchers at the University of Colorado, Boulder
have created the very first detailed map of the electric currents responsible for shaping
the magnetic field that wraps around Mars.
Not only are the visualizations stunning,
but they provide clues of how we can make this inhospitable planet one we can live on...maybe.
Let’s start with what we know so far. The region of space around a planet that’s
dominated by that planet's magnetic field is known as its magnetosphere.
Earth’s magnetosphere is driven by an internal dynamo,
a rotating mass of molten iron that’s located in our planet’s outer core.
The energy generated by the rising, cooling, and sinking of that molten iron
gets converted into a powerful magnetic field, which shields Earth from
the charged particles of solar and cosmic radiation and protects our atmosphere.
Unlike Earth, Mars doesn’t have a dynamo — and as a result, no intrinsic magnetic field
to stop charged particles from stripping away its atmosphere.
But this wasn't always the case.
Turn back the clock to about 4.3 billion years ago and Mars might have looked a lot more Earth-like.
It had a thick atmosphere and warm climate
capable of sustaining bodies of water like rivers, lakes, and even oceans!
All of this would have been possible if Mars once had a working dynamo of its own to protect its atmosphere.
But somehow, Mars transformed from a warm and wet place
into a cold, inhospitable desert.
There are a couple of leading theories as to what might have caused this dramatic transformation.
Some scientists believe that a series of giant asteroid impacts bombarded Mars over a period
of 100 million years. The idea goes that these impacts overheated the planet’s mantle
and stopped the dynamo, effectively killing off the planet’s intrinsic magnetic field.
Certain evidence suggests that Mars might have had a dynamo in only a single hemisphere.
And in fact, missions to the red planet have found remnants of a stronger magnetic field
in its southern hemisphere.
With a lopsided energy field, the planet’s atmosphere
would have been left vulnerable to erosion from the solar wind,
allowing it to collide with atoms in the upper atmosphere and eject them into space through a process
called “sputtering.”
As its atmospheric gas was slowly stripped away,
Mars’ atmosphere eventually became depleted enough to transform the planet into a cold, arid place.
Today, signs of Mars’ ancient intrinsic magnetic field still exist.
Since 2018, NASA’s InSight lander has been on the ground measuring the strength and direction
of the planet’s magnetic field and collecting detailed measurements of magnetic fields in the crust.
Because most of the rocks at Mars’ surface
are too young to have been magnetized by the planet’s former field, scientists speculate
that the sources of these crustal magnetic fields are rocks buried deep underground.
Located anywhere from a couple of hundred meters to several kilometers below the ground,
these older rocks formed before the planet’s dynamo shut down and remain magnetized,
acting as local mini-magnetospheres today.
By combining the measurements collected by InSight with satellite data,
researchers hope to identify exactly which rocks carry magnetism
and figure out how old they are.
While on the ground, InSight has also recorded
mysterious fluctuations in the strength and direction of the magnetic field between day and night.
Here’s how it works. The charged particles that make up the solar wind are
highly conductive, inducing electric currents that shape how energy flows into Mars’ atmosphere.
These currents cause a ‘pile-up’ of the magnetic field in the planet’s upper atmosphere,
until they become strong enough to create an induced magnetosphere.
By analyzing five years of data from MAVEN, researchers were able to piece together the
electric current systems in Mars’ atmosphere.
The initial results show how these electric currents
interact with the solar wind, causing it to wrap around the planet and form an induced
magnetosphere that offers Mars some protection.
Because while MAVEN and other previous missions
have seen hints of these currents before, this is the first time we’ve been able to map the complete circuit.
MAVEN’s goal is to explore the upper atmosphere,
and it’s not alone. Along with five other current Mars missions,
it’s trying to understand the potential for life to exist on Mars.
If we ever plan to put boots down on the red planet,
we’ll need to understand how important a magnetic field is for regulating climate.
Because while this work won’t bring back Mars’ thick atmosphere,
it may help us determine if Mars ever hosted life and if it could again.
Mars isn’t the only misfit without an intrinsic magnetic field.
Venus doesn’t have one either!
If you wish you had an interplanetary zip code of your own,
why not check out this video on terraforming Venus and Mars!
Is there any cool space phenomena you’d like to see us cover?
Let us know down in the comments below.
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