The surface of the Martian rock target in this stereo, close-up image includes small hollows with a 'swallowtail' shape characteristic of gypsum crystals The shapes left behind will be familiar to geologists who have studied gypsum crystals formed in drying lakes on Earth.
This image shows a mineral vein with bright and dark portions that distinguishes this Martian rock investigated near the upper edge of Vera Rubin Ridge In January 2018, Nasa announced that its Curiosity rover had spotted a set of mysterious ‘stick-like figures’ on the red planet.
Images beamed back from Mars by Curiosity appear to show patterns similar to Ordovician trace fossils Dr Di Gregorio has photographed here on Earth, he says.
Trace fossils are made by animals going about their lives, like footprints, burrows and waste matter, rather than the remains of the creatures themselves.
Speaking to the Daily Express, he said: 'If not trace fossils, what other geological explanations will Nasa come up with?
This image shows a trace fossil from the Logan Formation, found in east-central Ohio and parts of western West Virginia Dr Di Gregorio says fossils on Mars represent signs of soft bodied creatures which once roamed its surface.
This image shows trackways from a slug-like animal, from the Cambrian, found in Blackberry Hill, central Wisconsin'Nasa has turned its back on trying to get the data on this.
The order came down from HQ that they should move the rover on to the next point.'They didn't feel it was important enough to look at, I thought that was very odd, despite the fact Gale Crater was host to probably a series of lakes for billions and billions of years.'We're talking about something that might have been equivalent to the Ordovician period on Earth.' Dr Di Gregorio is not alone in his belief of evidence of life on Mars.
In recent weeks, a European space probe swung into position around Mars in preparation to analyse its atmosphere for possible signs of life The craft was inserted into an elliptical orbit around Mars in October 2016, and performed a series of maneuvers in January 2017 to shift its angle of travel so it can get the best view of Mars.
Further inspection of similar features by the rover elsewhere on Mars may resolve the timing of when the crystal-shaped features formed, relative to when layers of sediment accumulated around them.
Another uncertainty is whether the original mineral that crystallised into these shapes remains in them or was subsequently dissolved away and replaced by something else.
The agency says the orbiter will start looking for trace gases such as methane, which can result from biological or geological activity, in April.
It will also search for ice that could help future Mars landings.