Asteroid Crash May Have Demagnified Mars

[Dover]

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Asteroid Crash May Have Demagnified Mars

July 24, 2008 -- Scientists don't know what happened on Mars that caused its magnetic field to collapse. They suspect the planet's liquid metallic core cooled, ending convective currents that spread magnetic field lines through the planet's rock and soil and out into space.

But that may just be part of the story.

A team of researchers led by Jafar Arkani-Hamed of the University of Toronto in Canada believe a large asteroid circling the planet set up a gravitational tug-of-war that got Mars' core churning. Eventually, the asteroid lost its grip and crashed into its parent planet. Mars paid a dear price as well. Without the tidal forces, the planet's core lost its momentum, killing off the magnetic field.

What remain are patches of strong magnetic imprints in the oldest parts of Mars' crust. Because the fresher surface features are magnetic-free, scientists believe Mars lost its shield about four billion years ago.

Laboratory tests and computer simulations by Arkani-Hamed and colleagues and published in the Journal of Geophysical Research last month show a large asteroid circling about 46,000 miles above Mars could have had a strong enough pull on Mars to coax its liquid core into moving. The dynamic would have lasted about 400 million years before the asteroid crashed, demagnetizing Mars.

cont'd

http://dsc.discovery.com/news/2008/07/24/mars-magnetic-field.html

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Mars Got Slammed by a Big One

June 25, 2008 -- About four billion years ago, scientists believe Earth got smacked so hard by an asteroid or comet that a piece broke off to form the moon. Apparently, things weren't much better on Mars.

Three related studies appearing in this week's edition of the journal Nature provide evidence that Mars bears the biggest scar in the solar system -- an oval-shaped, 6,200-mile long impact crater that shattered half the planet's crust, left its southern hemisphere 2.5 miles taller than the north and possibly created the largest known string of volcanoes.

"Mars wouldn't be the planet it is today had this not happened," lead author Jeffrey Andrews-Hanna, with the Massachusetts Institute of Technology, told Discovery News.

The stark contrast between the hemispheres was first revealed by the Viking missions of the 1970s, which found low-lying plains in the north and older, heavily cratered highlands in the south.

Later studies showed the southern hemisphere had thicker crust than the north as well as some odd magnetic readings...cont'd

http://dsc.discovery.com/news/2008/06/25/mars-impact.html

[elleng]

1. 'Demagnetized?'

.

[RNdaSilva]

4. Degaussed?

[peacetalksforall]

2. Dontcha know that you're not supposed to refer to billions of years ago?

[Dover]

3. I really don't think I can take another sarcastic reference to creationism in this forum.

Been there, done that a thousand times already.

[Indenturedebtor]

5. So what your telling me then is that as part of our terraforming

We need to park a big asteroid in orbit :D

[Esra Star]

6. Well isn't that interesting

Demagnetising size asteroid impacts Mars 4 billion years ago.
Obviously masses of ejecta blasted into space. Most of this dislodged material which escaped Mars' gravity would have rained downhill (towards the Sun).
Magically life shows up on Earth 3 billion years ago. Hmmm, I wonder?

[Wilms]

7. I was thinking we're all "star stuff".

Perhaps we are Mars stuff.

[Esra Star]

8. Of course, ultimately, every atom in our bodies

was created in a supernova. Except, maybe, for any hydrogen.
Boggles the mind.