Mars’ growth stunted!

Mars is a weirdo. (Well, as far as planets go). Why is it so small (just 11% as massive as Earth)?

A cigar from another star

In Rendezvous with Rama (by Arthur C. Clarke), a mysterious object is discovered passing through the Solar System.  The object has a strange shape — it’s a giant cylinder.  It was discovered by the Spaceguard survey, designed to find objects that might impact Earth (so-called near-Earth objects).  Spoiler alert: the cylinder is a spaceship sent…