While the rest of us were on vacation over the holidays, the Mars Curiosity rover kept plugging away at its mission of exploring the Red Planet. It put some of the time into inspecting and photographing a set of fascinating stick-like formations on the Martian ground.

The rover team tweeted a good look at the small objects on Wednesday:

Meanwhile, back on Mars... I’m checking out these stick-like figures. Each is about a quarter-inch long. Maybe they're crystals? Or they could be minerals that filled spaces where crystals dissolved away. Stay tuned! Science continues. pic.twitter.com/4oR70BVht3 — Curiosity Rover (@MarsCuriosity) January 4, 2018

The rover's Mars Hand Lens Imager captured a whole series of images of the intriguing figures on Tuesday.

NASA scientists speculate the angular formations may be crystals or minerals that filled in spaces where crystals once formed, but then dissolved. We don't have any definitive answers yet, but it's another delightful example of how fascinating the small details of the Mars landscape can be.

Twitter users were eager to chime in with their own thoughts about what the formations might be. Snarky suggestions included tire tracks, the fossilized remains of a space dinosaur, sandworms, Viking runes or signs of Bigfoot.

As always, Mars offers plenty of fodder for the imagination, but the stick-like figures are no more signs of an alien civilization than this Martian pebble is a cannonball.