Could invisible aliens really exist among us? An astrobiologist explains
They probably won’t look anything like this. Martina Badini/Shutterstock By Samantha Rolfe, University of Hertfordshire Life is pretty easy to recognise. It moves, it grows, it eats, it excretes, it reproduces. Simple. In biology, researchers often use the acronym “MRSGREN” to describe it. It stands for movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. But Helen Sharman, Britain’s first astronaut and a chemist at Imperial College London, recently said that alien lifeforms that are impossible to spot may be living…