A MYSTERIOUS hole on Mars could be harbouring alien life in an extensive network of underground tunnels, according to Nasa. From orbit, scientists have captured a deep pit on the Red Planet that ...

But finally I hoisted myself up a 450-foot rope to the cave’s main entrance (dubbed Izhevskaya, or R21). I began to see why cavers think of Dark Star as a living, breathing entity. Down at base ...

When something goes wrong, if they don't solve the problem and make it back to the cave entrance before their ... of the inland blue holes—deep, dark, sheltered, with little tidal flow ...