Features of the comet, named 67P/Churyumov-Gerasimenko, such as its organic-rich black crust, are most likely explained by the presence of living organisms beneath an icy surface, the scientists have said.
Rosetta, the European spacecraft orbiting the comet, is also said to have picked up strange clusters of organic material that resemble viral particles.
The European Space Agency pulled off a sensational feat of engineering and captured the imagination of space-travel enthusiasts across the world when Philae landed on the comet in November. Since then, the lander has undergone a period of hibernation from which it awoke in June, having recharged its solar panels.
Neither Rosetta nor Philae are equipped to search for direct evidence of life after a proposal to include this in the mission was allegedly laughed out of court. Maverick astronomer and astrobiologist Prof Chandra Wickramasinghe, who was involved in the mission planning 15 years ago, believes people should be more open to the possibility of alien life.
Wickramasinghe said: "Five hundred years ago it was a struggle to have people accept that the Earth was not the centre of the universe. After that revolution our thinking has remained Earth-centred in relation to life and biology. It's deeply ingrained in our scientific culture and it will take a lot of evidence to kick it over."