20 aprile 2016. ESA’s Asteroid Impact Mission, currently under study for launch in 2020 and arrival in 2022, would be humanity’s first probe to a double asteroid system. Targeting an approximately 180-m diameter asteroid – around the same size as the Great Pyramid of Giza – AIM would spend a busy six months gathering data on its surface and inner structure.It would then perform before-and-after measurements as the NASA-led Double Asteroid Redirection Test spacecraft impacts straight into it, in an attempt to change the asteroid’s orbital period – marking the very first time that humanity shifts a Solar System object in a measurable way. Success would make it possible to consider carrying out such an operation again if an incoming asteroid ever threatened our planet. The two missions combined are called the Asteroid Impact & Deflection Assessment, or ‘AIDA’ for short.But why do we need to plan such a ground-breaking experiment? Astrophysicist and Queen guitarist Brian May, ESA astronaut Luca Parmitano, the UK’s Astronomer Royal Sir Martin Rees and Canadian astronaut Chris Hadfield share their own thoughts.