NASA’s Curiosity rover, which has been exploring the surface of Mars since 2012, has stumbled upon an unusual object, Aroged reported.

Some of the recent photographs of the rover, which has been transmitting images of Gale Crater to Earth for almost a decade, have caught the attention of writer Paul Scott Anderson. He noticed an unusual object on them, which hastened to share with Twitter users.

“Check out this groovy rock that the Curiosity rover just found on Mars yesterday,” he tweeted on February 15.

His post was the beginning of a lively discussion, during which users offered different options for the origin of such an unusual stone. Since liquid water was abundant on Mars in ancient times, it can be assumed that the smooth lines of the stone were given by liquid billions of years ago. It is also curious that NASA publishes images of Mars in the public domain, but Anderson said that he received a notice to stop illegal actions from a company that claims to own an NFT token confirming the right to own an image of an unusual stone.

Scientists who are exploring Mars have come to the conclusion that billions of years ago, crater lakes were common on the Red Planet. When the water in the crater became too much, it overflowed the edge, resulting in large-scale floods that cut through the river channels. Today, on the wind-dried surface of Mars, one can still see distinct traces of ancient rivers. It may well turn out that the stone found by the rover was polished by one of these currents billions of years ago.