On 18 March Alexander and the rest of the Expedition 40/41 crew, Maxim Surayev and Reid Weisman, will be in Houston, USA, holding a press conference. ESA is offering you the chance to have your Blue Dot question answered and have the crew reply live on NASA television. All you have to do is Tweet your question to @esa with hashtag #BlueDot. The best questions will be asked during the media briefing that can be followed live on NASA television 18:00–19:00 GMT (19:00–20:00 CET) on 18 March.
Full details are available on the ESA website: http://www.esa.int/Our_Activities/Human_Spaceflight/Astronauts/Ask_astronaut_Alexander_anything