for National Geographic News
The planet Mars may well have a liquid center, scientists say.
That's a surprise because Earth's core, which contains similar elements as Mars, has a solid, metal interior surrounded by a layer of molten metal.
The discovery was made by a team of European scientists using a device called a high-pressure anvil, which is capable of producing pressures of up to 6 million pounds per square inch (40 Gigapascals).
In experiments, the authors squeezed together high-temperature mixtures of iron, nickel, and sulfur to replicate conditions found on Mars. The researchers were able to determine that the Martian core is still mostly, if not entirely, liquid.
(See related: "Mars Has Liquid Water, New Photos Suggest" [December 6, 2006].)
They were also able to predict what will happen as Mars continues to cool.
Depending on the precise mix of nickel, iron, and sulfur, said study lead author Andrew Stewart, a geochemist at the Swiss Federal Institute of Technology in Zurich, two scenarios are possible.
The Martian core could solidify from the outside in.
This will cause nickel-iron crystals to slowly rain toward the center like metallic snowflakes, accumulating in what Stewart pictures as a giant metallic snowball.
The other prospect is that the Martian core would solidify from the inside out, but that the interior would be comprised of sulfides, or compounds containing sulfur, rather than metal.
"Both of these are completely different from what the Earth does," Stewart said. "Which will occur depends on how much sulfur is in there."
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