NASA’s Curiosity rover captured an intriguing image of a minuscule Martian boulder that resembles a fossilized book on the Red Planet’s surface.

The image was acquired by the Mars Hand Lens Imager (MAHLI) on the end of the rover’s autonomous arm on April 15 — the 3,800th Martian day, or sol, of the mission, according to NASA(opens in new tab). The red rock resembles two halves of an open book with one page that has suspended in the middle of being turned.

The object may resemble a book, but it is significantly smaller. NASA reports that the fossilized pageturner measures only 1 inch (2.5 centimeters) in diameter.

On Mars, the rover found a little rock that resembles a preserved book.

“Rocks with unusual shapes are common on Mars,” NASA representatives wrote. The peculiarly shaped boulders are composed of minerals left behind by ancient water. They added that these minerals were once concealed beneath softer sediments, but billions of years of wind erosion have swept away everything else.

In February 2022, Curiosity noticed a branched “mineral flower” that measured approximately 0.4 inches (1 centimeter) across. And on February 16, the rover captured images of boulders imprinted with minuscule ripples or waves from an extinct lake.

Scientists have also observed larger-scale shapes chiseled out by ancient water on Mars, including a large rock formation that resembles the visage of a teddy bear and another that resembles the Muppet Beaker.

A few images captured by curiosity are more striking than puzzling. The rover captured the first images of “sun rays” on Mars on February 2, which occur when sunlight penetrates through cloud openings during sunsets or sunrises when the sun is below the horizon.