Facebook adds strange, unexplained rocket icon to some people's accounts

Facebook has added a new icon to some people's home screen – and not explained why it is there. Selected users are now seeing a small rocket at the bottom of their screen, without any clue about what to do with it or what it means. Clicking on the rocket appears to lead to an altered version of the news feed, but the traditional one still exists alongside it. The button is appearing for selected users on iOS and Android at the bottom of the app's view. It sits between the normal news feed and the friends option.