Flakes of iron snow could be falling inside the planet Mercury, according to a new experiment. This hot metal snowfall might help generate Mercury鈥檚 puzzling magnetic field.
Researchers in the US have attempted to recreate the likely conditions within Mercury鈥檚 liquid outer core, which is thought to be a mixture of iron and sulphur.
They used an arrangement of magnesium-oxide blocks, called a multi-anvil cell, to squeeze their iron and sulphur mixture to immense pressures, at temperatures above 2000 掳Celsius. Iron crystals formed in the mixture.
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鈥淲e saw iron crystals gathered at the bottom of the sample, while the liquid phase stayed on top,鈥� says team member Jie Li of the University of Illinois in Urbana-Champaign. Mercury鈥檚 iron snow should form simple cubic crystals, rather than the intricate hexagonal patterns of water-ice snowflakes on Earth.
Convection patterns
The detailed weather forecast for Mercury鈥檚 interior depends on exactly how much sulphur is added to the mix. There may even be two layers of snow clouds, each slowly sprinkling iron crystals down onto the solid inner core.
This process is likely to affect patterns of convection in the core, and therefore the magnetic field.
In Earth鈥檚 liquid iron outer core, convection currents generate our planet鈥檚 relatively strong magnetic field in a process called the geodynamo. The mercurodynamo must work a little differently, as Mercury鈥檚 field is probably less than 1% as strong as Earth鈥檚.
鈥淣o one knows how exactly this influences the magnetic field, but a snowing core is certainly different from the Earth鈥檚 core,鈥� which is solid from the bottom up, Li told New Scientist.
Mercury鈥檚 inner structure and the nature of its magnetic field should become clearer after NASA鈥檚 Messenger mission arrives at the innermost planet in 2011.
Journal reference: (vol 35, page L07201)
