Scientists claim to have found fossils in rocks from southwest Greenland that are the oldest physical evidence of life on Earth and raise questions of life on other planets during that period, The Guardian reported on Thursday. The scientists believe that the fossils, formed 3.7 billion years ago, are stromatolites – layered formations produced by microbial activity.

The report quoted co-author of the paper, Clark Friend, who said, “Up until now, the oldest stromatolites have been from Western Australia and they are roughly 3,500 million years old. What we are doing is pushing the discovery of life earlier in Earth’s history. If we have got life at 3,700 million years on Earth, did it exist on other planets – because Mars, for example, 3,700 million years ago was wet.”

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The report also quoted Lewis Dartnell, an astrobiologist at the University of Westminster, who said that this discovery could prove to be pathbreaking in the study of life on other planets as stromatolites are normally destroyed by plate techtonics and the metamorphism of rocks. Dartnell said, “The Martian surface today is very cold and dry, but around the time that these ancient layered rocks formed in Greenland, Mars was itself a much warmer and wetter, and thus habitable planet.”

Friend and his Australian team’s article in the journal Nature, says their discovery in Greenland's Isua supracrustal belt was a surprising one. They said such fossils, formed from sedimentary rocks that have undergone extreme heat and pressure, generally get deformed as a result. The melting of a snow patch led to their discovery.

The formations, visible on the rock's surface, are peak-like structures 1-4 cm in height, and bear resemblance to a shark's tooth. Nick Lane, an evolutionary biochemist at London's University college, said the study indicates that the planet, during that period, was not as inhospitable as it was previously thought to be.