NASA's Curiosity rover has just drilled its first hole in the foothills of Mount Sharp, the 3-mile-high (5-kilometer-high) mountain on Mars that's the primary destination for the six-wheeled machine's $2.5 billion mission. The 0.63-inch-wide (1.6-centimeter-wide) hole looks perfect for a game of super-miniaturized golf — and if Curiosity's handlers ever want to play a round, they know just where to look for a ball.
A couple of weeks ago, while Curiosity was making its way toward the Pahrump Hills outcrop on the base of the mountain, the rover snapped pictures of the surrounding landscape. One weird feature sparked attention across the Internet — a seemingly perfect sphere sitting on the rocks. Nearby, Curiosity's camera caught a view of an even stranger formation that looked like a string of balls or an alien "traffic light."
As mysterious as they look, the formations have a straightforward explanation: They're concretions similar to the "blueberries" that NASA's Opportunity rover came across 10 years ago on Mars — only larger.
The spherules were formed billions of years ago when mineral-rich water seeped into pores within sedimentary rock. Layers of an iron mineral known as hematite built up gradually to fill the space in the pores. Later, when the softer rock eroded, the hematite spherules were left out in the open. It's a process similar to the one that created the weird "moqui marbles" seen in Utah and Arizona.
The "traffic light" formed as a dendrite — a tree-like branching structure that's bound together with mineral deposits.
"By investigating the shapes and chemical ingredients in these features, the team hopes to gain information about the possible composition of fluids at this Martian location long ago," NASA said in a statement on Friday.
As big as they look in Curiosity's pictures, the Martian spherules are smaller than golf balls. The lone spherule sitting on the rock is about a half-inch (a centimeter wide) — which makes it as big as a garden-variety toy marble, perfect for shooting into the hole that Curiosity just drilled.
For better or worse, Curiosity's science team won't be playing games anytime soon: The powder that was drilled out from the hole on Wednesday, at a place nicknamed Confidence Hills, is being held within the sample-handling mechanism on the rover's robotic arm. Eventually the sample will be subjected to chemical analysis in the rover's onboard mini-labs.
Similar tests revealed the geological history of Yellowknife Bay, an area that scientists now say could have sustained life billions of years ago. Curiosity's team hopes the samples from Confidence Hills will yield further insights about Mars' transition from a potentially habitable planet to an inhospitable one.
"This drilling target is at the lowest part of the base layer of the mountain, and from here we plan to examine the higher, younger layers exposed in the nearby hills," Ashwin Vasavada, the Curiosity mission's deputy project scientist, said in Friday's update. "This first look at rocks we believe to underlie Mount Sharp is exciting, because it will begin to form a picture of the environment at the time the mountain formed, and what led to its growth."