What looked like a piece of metal protruding from a piece of rock had tongues wagging. It turns out, it's a piece of shiny rock — a lot like some we see here on Earth.

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NASA

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NASA

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NASA

The image, taken by Mars rover Curiosity in January has sparked debate because of the shiny object marked by the yellow arrow.

NASA/JPL-Caltech/Malin Space Science Systems

Last week, a blogger at Universe Today began a bit of an Internet frenzy when a reader spotted a shiny object in one of the pictures taken on Mars by the Curiosity rover.

There it was, a piece of what looked like shiny metal sticking out from a rock. It's not the first time the Mars rover Curiosity had spotted a shiny object. The last time around — back in October — a very small, plastic-looking object created the same kind of speculation. (Could it be?) It turned out it, the plastic looking thing was likely a piece of the spacecraft that dropped the rover off in Mars.

Today, NASA sent an analysis of the latest image from Ron Sletten, a team collaborator who studies soils at the University of Washington.

No, Sletten said, this is not a piece of debris from an alien spacecraft. It's actually a piece of rock that is more resistant to erosion than the rock it's embedded in.

"The rock on top of the projection is likely more resistant to wind erosion and protects the underlying rock from being eroded," he writes. "The shiny surface suggests that this rock has a fine grain and is relatively hard. Hard, fine grained rocks can be polished by the wind to form very smooth surfaces."

In some ways, said Sletten, it's a lot like what happens to rocks in Antarctica.

Sletten put together a slideshow that explains his thinking:

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