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t’s the smallest planet in our solar system, and it might be getting even smaller. New research suggests that Mercury is shrinking!

Messenger, a NASA spacecraft, recently flew within 125 miles of Mercury’s surface to take photos of the planet. The spacecraft will pass the planet twice more and eventually enter the planet’s orbit. Messenger will collect information about Mercury’s core.

Messenger has already sent back more than 1,000 pictures. By studying the photos, scientists determined that Mercury once had many active volcanoes on its surface. They suspect that the planet’s outer core, an area deep under the surface, is made of magma. As the magma gradually cools, it contracts. That causes the planet to shrink.

“It’s a pretty cool thing,” says Mark Robinson, a researcher at Northwestern University who is studying Mercury. “When I first heard it, I thought it was weird.”

The photos also reveal Mercury’s more colorful side. In the past, Mercury has been compared to Earth’s gray, crater-covered moon. But the new pictures show that the planet has colorful craters. “It has very subtle red and blue areas,” says scientist Louise Prockter of Johns Hopkins University.

Scientists are also seeing a pattern of ridges on Mercury’s surface that looks like a giant spider. It’s “unlike anything we’ve seen anywhere in the solar system,” says lead researcher Sean Solomon. He says the ridges may be further proof that the planet is shrinking. As the planet contracts, parts of the surface are pushed on top of one another, causing ridges to form.

Mercury is 3,031 miles in diameter, which makes it a little larger than Earth’s moon. The little planet is a big mystery to scientists. Researchers believe the inner core is made of iron. However, they do not know how large the core is or whether it rotates. Messenger will track how the planet wobbles to find out more about the core.

The last NASA spacecraft sent to Mercury was the Mariner 10 in 1975. It took pictures of only 45 percent of the planet. So far, the $446 million Messenger mission has taken pictures of 30 percent of Mercury, but it will take pictures of the whole planet by the end of the project. Mercury, say cheese!

Why, do you think, is so little known about Mercury?

Learn more about Messenger and Mercury here.

Are you an ace when it comes to space? Test your
solar system smarts and find out!



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