Nasa Curiosity mission finds book-shaped rock on Mars

In a rare discovery made on the Martian soil, Nasa's Curiosity rover found a rock which looked like a book on its 3,800th day on the red planet.

The close-up view was captured by Nasa Mars Mission on April 15 and dubbed "Terra Firme".

According to Nasa officials: "The strange shape of Mars rocks like this one are usually due to water trickling in the area billions of years ago when the Red Planet was much wetter."

According to a Nasa blog post, rocks with unusual shapes are common on Mars and often were formed by water seeping through cracks in a rock in the ancient past, bringing harder minerals along with them.

After eons of sand-blasted by the wind, softer rock is carved away and the harder materials are all left, it added.

Curiosity mission — led by NASA's Jet Propulsion Laboratory (JPL) — took the selfie using a camera called the Mars Hand Lens Imager (MAHLI), located on the end of its robotic arm. MAHLI was built by Malin Space Science Systems in San Diego.

JPL said: "Curiosity has been exploring Mars' Gale Crater since August 2012, with key results in science papers including the discovery of persistent liquid water on ancient Mars, potential evidence of ancient life through organics, and examinations of radiation at the surface."

Another Nasa's Mars mission Preservance Rover is continuing its work in the Jezero Crater area of Mars and caching tubes of samples for bringing it back to Earth for further investigations.

The return of the samples from Mars is likely to be at the end of 2020s with the launch of a set of relay spacecraft and a couple of mini-helicopters.