Prof John Parnell, 55, has co-written a theory with Dr Joseph Michalski, a planetary geologist at the Natural History Museum, that suggests they have discovered the best signs of life in the huge McLaughlin Crater on the surface of Mars.

The document, published today in Nature Geoscience journal, describes how they assessed the crater, created by a meteorite which smashed into the surface of Mars, flinging up rocks from miles below.

The rocks appear to be made up of clays and minerals which have been altered by water – the essential element to support life.

Speaking from his laboratory at the University of Aberdeen, geochemist Prof Parnell said: “We could be so close to discovering if there is, or was, life on Mars.