NASA's Curiosity rover captures dawn on Mars

NASA has released a striking image of dawn on the Martian surface taken by its Curiosity rover, showing sunlight bathing jagged crags formed billions of years ago.

Curiosity, which is about the size of a Mini Cooper, landed in 2012 in Gale Crater near the Martian equator, and since 2014 has been climbing Mount Sharp, a 5 kilometre-tall mountain rising from the crater floor. 

The image was taken by the six-wheeled rover's Mastcam camera about an hour after the sun rose above a landscape featuring wind-carved cliffs in the distance, in August.

"The bright craggy peaks in the distance are a rock layer that is quite different in appearance from all the layers the rover has driven through so far," said planetary scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory in California.

"We think it once was wind-blown sediment, maybe sand or maybe even ash that blew into the crater from nearby volcanic activity. 

"After the sediment hardened into rock, eons of wind carved up the rock layer into ridges called yardangs," the Curiosity project scientist said.

The yardang layer most likely formed about 3 billion years ago, around the same time as the rest of the mountain, according to Mr Vasavada.

This layer spans about 16 kilometres across the north-western reaches of Mount Sharp.

"However, the yardang layer doesn't appear to be part of the continuous stack of layers that make up the layer-cake of Mount Sharp. It was added on a little later. It's above what geologists call an unconformity: a gap in time where previous layers eroded down before new layers were deposited on top," Mr Vasavada said.

'You can almost feel the silence'

The rover on its gradual ascent up the mountain has gained upwards of 1km in elevation, the most ever climbed on Mars, according to NASA.

Mount Sharp is built of layers, each recording a period of the planet's geological past. In studying these layers, scientists have learned more about bodies of water — lakes and streams — that long ago covered this region, at a time when Mars was wetter and warmer than the cold and desolate place it is today.

Mr Vasavada said NASA hopes Curiosity will reach the yardang layer in 2027 or 2028, at which time it will use its instruments to scrutinise the geology there.

Curiosity has been studying the geology and climate of Mars and examining whether it once bore conditions conducive to harbouring microbial life. 

It is one of two NASA rovers operating on Mars. 

The Perseverance rover is currently traversing the margins of Jezero Crater in the northern hemisphere.

Curiosity's new image of Martian dawn is certainly otherworldly.

"This scene has a wildness that reminds me of a road trip through Monument Valley, Arizona," Mr Vasavada said.

"You can almost feel the silence and the endless open space under the sky. But as familiar as that sounds, the sky is orange and the sunrise has shades of blue. It's like Earth, but it's definitely Mars."