A donut-shaped rock showed one of the images of Mars sent by NASA’s Perseverance rover. Strange objects have been spotted on Mars from time to time, but this time the new image really tested the inspiration of Twitter users.

Baffled Twitter users have suggested a number of ideas for what the rock could be, including an alien toilet or “an egg of some sort”.

However, experts believe there may be a more reasonable explanation, and think it’s more likely a meteorite that fell to Mars from the sky.

Perseverance took the photo on June 23 and was shared on Twitter by the SETI (Search for Extraterrestrial Intelligence Institute). NASA’s Mars 2020 mission launched in 2020 to search for signs of ancient life on the red planet. The $2.5 billion Mars 2020 spacecraft launched on July 30 with the Perseverance rover and the Ingenuity helicopter on board and landed successfully on February 18, 2021.

The car-sized rover is exploring an ancient river delta inside Jezero Crater, which was once filled with a 1,600-foot-deep lake. The region is believed to have hosted microbial life around 3.5 to 3.9 billion years ago, and the rover will examine soil samples to look for evidence of life.