Last week, Nasa held the first public meeting of a panel established to investigate sightings of UFOs. It came just before a whistleblower former intelligence official told the Debrief that the US government had ‘intact and partially intact’ craft of non-human origin. Ian Sample talks to Prof David Spergel, the independent chair of Nasa’s panel, about why this is happening now, what they hope to find and why there is so much stigma attached to this field. Help support our independent journalism at theguardian.com/sciencepod