Mars Missing Magnetic Field -Was It Destroyed by a Massive Asteroid Impact?


If you've seen The Core then you that the only thing between us and instant space-death is a magnetic field.  You also know that's the only thing that's even heard of real science in the entire movie, but it's a pretty important one – and could explain why the otherwise eminently habitable Mars is such a barren wasteland.  Scientists think the Martian magnetic field might have been hammered into submission by strikes from space. (The image above shows the the Syria, Sinai, and Solis Planum impact areas).

Planetary magnetic fields are created by massive molten metal currents within the planet's core.  A flowing current creates a magnetic field, even when the current is massive volumes of charged liquid metal moving under the influence of temperature gradients (convection) – in fact, especially then.  But magnetic analysis of Martian sites by Berkeley researchers show that the red planet's protective field was switched off half a billion years ago, and now some scientists say they know why.

All was pure speculation until data came back from the Mars Global Surveyor and other recent spacecraft. In 2009, planetary scientists Robert Lillis and Michael Manga, both of the University of California, Berkeley, linked age estimates of impact basins with magnetic field strength to show that the previously established date of heavy bombardment, about 3.9 billion years ago, corresponds to the death of Mars's dynamo.

Lillis, Manga, and planetary geophysicist James Roberts of John Hopkins University Applied Physics lab in Laurel, Maryland, modeled the effects of heat produced by impacts and calculated that a period of massive asteroid impacts, known to have happened around the same time, could not only have massively impacted on the surface Deep Impact-style (with all the atmospheric alteration and great-big-crater-making that entails) but added enough energy to the planet to heat up the outer layers of the planet.

Without the huge temperature difference between the core and mantle, the mega-magnetic dynamo convection currents would be switched off – and unable to start up again when things cooled down.  Remember, planetary core behavior is still carrying on from when the planets first formed – as far as they're concerned the whole "crust" thing and all life as we know it is just a cooling scum on the surface.  If you break something from back then you just don't have the juice to start it up again.

Without the magnetic field Mars is defenseless against the radiation that constantly pours in from space (never mind the Fantastic Four, the only superpower cosmic rays'll give you is decomposition).  Earth is thought to have survived the same space-bombing because of our superior size, with our dynamo maybe stuttering a little but – very importantly – not stopping.

As you can maybe tell by the fact you exist.



Luke McKinney and Casey Kazan.

Did Mars' Magnetic Field End With A Bang Or A Whimper? 


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