Maybe it would be okay for Ash to talk about home. Nel did, so it would be fair to return her kindness by telling her about himself.

"Yeah. The whole island is one big desert. The sun is so unbearable there that people can only live on the edge of it where they can get supplies from other continents, like Windmill Promontory or Monetopia."

Ash gazed up at the ceiling as he spoke, thinking back to his homeworld.