When we consider the development of planets, we tend to visualise heat, turmoil, and time lingering for billions of years. But Mars, as it turns out, did not require so much time. In a new study, scientists discovered that the Red Planet developed its core at a much quicker pace than Earth. The scientists came to the conclusion after conducting experiments at NASA's Johnson Space Centre.
Core of Mars developed in a few million years
New science indicates that Mars' core formed rapidly. The evidence puts it at just a few million years after the solar system started. That's faster than Earth, whose core formed in a billion years or more.
This is based on how molten metal migrated. In early Mars, molten iron and nickel sulphides migrated in solid rock. They went down to the centre of the planet prior to the time the interior became completely molten. This was never directly evidenced before but has been proven now.
The theory, known as planetary differentiation, describes how planets differentiate. The heavy metals, such as iron and nickel, descend to the core. Lighter elements stay closer to the surface and mantle. But until recently, researchers assumed molten interiors must be formed first. Radioactive decay would heat up the rock, melting it typically. Then metals would be able to flow down.
That is how Earth's core probably came about. But Mars did it quicker, it appears. Scientists looked to Martian meteorites for answers. The meteorites contain radioactive material, providing a window into Mars' early core.
NASA team puts new theory to the test
To prove their hypothesis, researchers simulated early Martian environments in a laboratory. The research was led by Sam Crossley, who is currently at the University of Arizona. In NASA's Experimental Petrology Lab, the team heated up rock samples to more than 1,020°C. That's hot enough to melt sulphides, but not silicates.
They next imaged the samples with 3D X-ray. This revealed molten sulphides flowing through cracks in solid rock. These melts penetrated to the core rapidly, even in a solid centre.
Crossley explained that the team observed these flows in the 3D images. The molten metal flowed through the sample, as they would have predicted.
To verify that the process occurred in space, the researchers examined meteorites. They looked for platinum-group metals such as iridium, ruthenium, and platinum. These metals serve as fingerprints of molten sulphide movement.
Jake Setera, another researcher at ARES, employed laser ablation methods. His technique followed traces of the unusual metals without destroying samples. He detected patterns of metals in lab specimens that were similar to actual meteorites. That proved that sulphides migrated through solid rock during early Mars.
Setera's study bridged laboratory results with cosmic data. The results correlated with metal traces in oxygen-rich meteorites. That provided solid evidence for the team's hypothesis.
A model for other worlds as well
The evidence indicates that Mars developed its core quicker because of where it was. In the early days of the solar system, planets developed within a disc-shaped cloud of dust. The inner part contained heavier metals such as iron and nickel. The outer part contained lighter elements such as hydrogen and water.
Mars developed between those two zones. It had light elements and heavy metals such as sulphur available. That accelerated the process. Molten sulphides could travel relatively fast, creating a sulphur-dense core.
This would also be the case for other bodies in that mid-zone. Not only Mars, but any planet developing in this kind of position.
The research, which was published on 4 April in Nature Communications, predicts that Mars' core ought to have high levels of sulphur. And what does sulphur smell like? Rotten eggs.
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