Search This Blog

Thursday, 23 October 2014

Tiny Space Magnets!!

So, what's it all about?

Tiny space magnets, you say?
Since doing an MSci project and starting a PhD, it's become increasingly apparent that it's really hard to explain to other people what my research is actually about.  I still don't really understand what some of my closest friends did for their masters, even the ones doing Earth Sciences.  Graduate fresher's week was a mine field of all the usual questions: 'Where are you from?', 'How long have you been here?', 'Where are you living?' and of course 'What do you study?' (ensue polite nodding and 'how interesting' comments accompanied by blank expressions).  My parents also have no idea what I do, despite many attempts to explain, which usually result with 'That's nice dear, we're very proud' followed by my work being quietly shuffled to the bottom of a pile of I Love my Cat and Help I'm Middle Aged articles.  As far as everyone else is concerned, I may
 as well be studying the dynamics of tiddlywinks on Mars.

I now just resort to telling people I study 'tiny space magnets', but here's an elaboration.  I'm working as part of a research group studying nanopaleomagnetism.  Nanopaleomagnetism isn't a particularly helpful term, unless you're trying to end conversations very quickly at dinner parties.  To translate, it basically means we look at very small scale structures on the scale of a billionth of a metre to try and understand what rocks can remember about magnetic fields they've been exposed to over geological time.  I am currently looking at meteorites and the magnetic fields they remember from the early solar system, when they were part of planets or asteroids, before they were smashed to pieces and found their way to Earth.

A stony-iron meteorite made up of olivine gems surrounded by
iron-nickel metal which contains tiny structures recording ancient
magnetic fields.

Some of the tiny structures we look at in the search for ancient magnetic fields.  These photos were taken using a reflected light microscope.

Why are we interested?

The Earth has its own magnetic field, which is why we have a north and south magnetic pole and you can navigate using a compass.   This magnetic field is generated by the Earth's core which is metallic, and has an outer, liquid region which is vigorously mixing - it's essentially the same as passing a current through a coil to generate a magnetic field.

The Earths' magnetic field is very important for many reasons:

- It shields us from harmful cosmic rays
- It holds onto our atmosphere, allowing life to develop
- It provides invaluable dating information when looking into the geological past
- It helps us to understand the dynamics of our core, which we can't directly observe

Shielding provided by the Earth's magnetic field

The magnetic field also flips, so the north pole becomes the south pole and this occurs with a varying frequency but usually every few hundred thousand years.  The dynamics of this are still poorly understood, but it this flipping provides a unique record for understanding past plate tectonic motions.

This shows sea floor spreading, where oceanic crust is created when tectonic plates pull apart.  The black and white stripes show the magnetic field switching which is remembered by the crustal rocks.  Look how symmetric the stripes are around the spreading centre - this was an important clue when people were looking for evidence of plate tectonics.

  The magnetic fields that meteorites have been exposed to may have been generated by the planets or asteroids they were a part of generating their own magnetic field; this means they probably had a partially molten metal core, much like that of the Earth.  By studying these fields we can start to constrain things like how planets collided and interacted when they were hurtling around in space before everything settled down to orbit the sun as it does today.  We can also think about how planets formed; Did they cool quickly?  Did they form in one go, or were bits added later?  Did it separate out into layers with a metal core?  Since we can't travel back in time, launch ourselves into space and look at these planets (and even if we could, we couldn't see inside them) tiny space magnets are one of our best bets for figuring out how our solar system and planet formed.

Tiny space magnets can help us to understand planetary collisions and
formation in the early solar system.

No comments:

Post a Comment