The claim that alien bacteria had been found high up in the Earth’s atmosphere was greeted with a large degree of scepticism on Tuesday. Professor Chandra Wickramasinghe, from Cardiff University, UK, told a weekend conference that a balloon flight at an altitude of 41 kilometres had recovered clumps of microbes that most probably had their origin in outer space. But scientists working in the field of astrobiology – the study of life in the Universe – said they had yet to be convinced by the Cardiff evidence.