Scientists studying rocks from the Western Isles say their work could provide clues to the existence of life on Mars.

Aberdeen University researchers have shown hydrogen, one of the essential building blocks of life, can be produced by earthquakes.

They believe tremors on the Red Planet may have the same effect after studying the process in rocks from Barra and Uist.

Nasa plans to study seismic activity during its InSight mission to Mars in 2018.

Professor John Parnell, from Aberdeen University's School of Geosciences, said: "Earthquakes cause friction and our analysis of ancient rock in the Outer Hebrides has demonstrated how this creates hydrogen.

"Hydrogen is a fuel for simple microbes, so microbes could live off hydrogen created in the Earth's subsurface as a result of seismic activity.

"This is a model that could apply to any other rocky planet, and on Mars there are so-called 'Marsquakes' that may produce hydrogen and therefore could feed life in the Martian sub-surface."

He added: "Our analysis finds that conservative estimates of current seismic activity on Mars predict hydrogen generation that would be useful to microbes, which adds strength to the possibility of suitable habitats that could support life in the Martian sub-surface.

"Nasa has plans to measure seismic activity on Mars during its 2018 InSight mission, and our data will make those measurements all the more interesting."

The results of the study, which was carried out alongside experts at Yale and Brock universities, has now been published in the journal Astrobiology.

Last year, scientists at the University of Aberdeen managed to extract methane from a volcanic Martian rock which arrived on Earth as a meteorite.

They say the gas could be used as a food source by simple life living beneath the planet's surface.

Nasa's InSight project will study the deep interior of Mars in an attempt to understand the processes which formed the rocky planets of the inner solar system four billion years ago.