From Jim McHardy, Clydebank, West Dunbartonshire, UK
It has been suggested that the elongated interstellar object ‘Oumuamua was sent to our solar system by advanced alien life (2 September, p 29).
However, natural explanations seem more likely. Lava solidifying in a volcano conduit often takes up a rod-like ‘Oumuamua shape. Erosion of the surrounding rock leaves the frozen lava as a volcanic plug. ‘Oumuamua could have formed like this on a distant planet. A later collision with another object could have ejected the plug into space. Or the close pass of its planet to a star may have increased the temperature and pressure of magma so much that it fired a rod of frozen lava upwards from a volcano fast enough to escape from a small planet.
