"An Impact Basin as Deep as Mount Everest" --Was Mars' Magnetic Field Destroyed by a Colossal Asteroid?

 

          

An impact basin deep enough to swallow Mount Everest and surprising slopes in Valles Marineris highlight what might be the results of a ancient asteroid collision with the Red Planet. 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 NASA scientists say they know why. 

"The full range of topography on Mars is about 19 miles (30 kilometers), one and a half times the range of elevations found on Earth," noted Dr. David Smith of NASA's Goddard Space Flight Center, Greenbelt, MD, the principal investigator for MOLA. 

"The most curious aspect of the topographic map is the striking difference between the planets low, smooth Northern Hemisphere and the heavily cratered Southern Hemisphere," which sits, on average, about three miles (five kilometers) higher than the north, Smith added. The MOLA data show that the Northern Hemisphere depression is distinctly not circular, and suggest that it was shaped by internal geologic processes during the earliest stages of martian evolution. 

The massive Hellas impact basin in the Southern Hemisphere is another striking feature of the map. Nearly six miles (nine kilometers) deep and 1,300 miles (2,100 kilometers) across, the basin is surrounded by a ring of material that rises 1.25 miles (about two kilometers) above the surroundings and stretches out to 2,500 miles (4,000 kilometers) from the basin center. 

This ring of material, likely thrown out of the basin during the impact of an asteroid, has a volume equivalent to a two-mile (3.5-kilometer) thick layer spread over the continental United States, and it contributes significantly to the high topography in the Southern Hemisphere. 

The difference in elevation between the hemispheres results in a slope from the South Pole to North Pole that was the major influence on the global-scale flow of water early in martian history. Scientific models of watersheds using the new elevation map show that the Northern Hemisphere lowlands would have drained three-quarters of the martian surface. 

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. 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.

John Hopkins University scientists 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.

The Daily Galaxy via http://science.nasa.gov/science-news and sciencemag.org

Video of Hellas Basin

Image credit: With thanks to http://jules.unavco.org/Voyager/Docs/ImageGallery

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Comments

[dr burke]

Would a neutron bomb re-energize it? Like jump starting Mars magnetic field?

[Harkabir]

Very important topic this. Thanks for writing on it.

I would like to suggest cutting back on the pop culture and Hollywood references. Some key concepts/events in the article haven't been explained. Rather the writer assumes that the reader has seen the referenced movies and understands or remembers the events in them. I have seen all the movies mentioned above, I like all of them (particularly Deep Impact) for their entertainment value and could even recommend a few more (go here http://marsmovieguide.com/). However I do request you to re-think this path as it is disservice to those who haven't seen these movies.

Thanks again and look forward to reading more on this topic.

[A paulo]

. Venus could've done with one of those to shut down the ridiculous volcanism.(without throwing molten material at earth). Earth must have copped some of that planet killer event of Mars.

Question is will Venus eventually cool itself down or blow apart?

[Velocity_Wave]

@A Paulo:
Interesting point: I wonder how Venus' evolution would be, if it's core had been shut down in a similar way as to Mars? In Venus' case it may have been a positive, and actually made the planet more habitable to life than it is now.

Going forward, I suspect the future of Venus depends upon the future of human civilization.

If civilization continues to evolve at it's current rate, I would not be surprised if humans begin (sometime in the next 50 to 100 years) to make efforts to cool Venus.

Giant solar shades and reflectors in orbit around Venus (based upon nano-engineered materials) could do the trick nicely and very rapidly bring down the temperature.

[Rowhider]

Maybe, but what doing of sulfuric acid oceans?! To get Venus habitable, we shall completly change the athmosphere composition to have something less aggressive to our technologie. Secondly I beleive the pressure is very high... Mars is far more freindly for humans.

[Cameron]

The author refers to MOLA like we know what it is. At the first introduction of an acronym, please write out the full text and put the acronym in parentheses (or the opposite).

[Mark T]

It's interesting to see the other comments. I suspect that humans or our machine surrogates, if we manage to get off-world in the next 100-200 years, and then manage to build up substantial industrial power in space, will start engineering most of the bodies of the inner solar system.

Mars - by comparison is the training wheels world, terraforming Mars is trivial when comparing to Venus, since lower gravity means that we have the materials know-how to build a space-elevator on Mars , today.

Venus seems to be a mega-engineering project in comparison, nearly the size of Earth, a hostile/toxic high-pressure atmosphere, totally jacked up rotation and not a drop of water anywhere.

[Quenton Gaspari]

I think that an idea would be to mine the material from the Hellas Basin and use explosions to dislodge the material inside to turn on Mars magnetic field...much like a sliver in a foot sort of speak. the only worry if this theory turns out to work is ...olympus Mons & other volcanoes get back pressure or set off , and the amount of danger from the dynamo that close to the core where the miners & drills are would be attempting to turn-on mar magnetic field...and the reverse impact or positive cataclysm event that would change Mars to a planet more similar to Earth then it is now...... hopefully Im right with the theory , it would make no need or less work for terraforming.