In that interval, Tom, you must write the book you've wanted to write - no, not the book you were working on for them, son, no, for they're dead and gone and it can't be changed. No, this time it's a book for us, living, that's the book we want. A book you can leave with us, for you, a book bigger and better in every way than anything you ever wrote; say you'll do it, Tom, say you'll dig a short text about Mars?

HINT: Wikipedia may work not over HTTP
HINT 2: digging is the right way to get flag