There's an old penny on Curiosity that the robotic probe uses to calibrate the Mars Hand Lens Imager at the end of its arm. The rover recently took a hi-res close-up of the coin, and as you can see, it's getting a little dusty.

This is the most expensive penny in the Universe. It's now on Mars, after an exciting $2.5 billion ride. Previously, the most expensive Lincoln penny in history was a 1943 copper-alloy cent that was sold for $1.7 million in a 1996 auction. That's peanuts compared to the cost of putting this coin up there, however.

The Mars Science Laboratory — also known as MSL, or Curiosity — is the most sophisticated Martian vehicle that NASA has ever built. And it's set to launch for the Red Planet tomorrow.