Franklin expedition: Will we ever know what happened?

Canadian explorers have drawn a blank in the latest hunt for the remains of Captain Sir John Franklin's fatal expedition, 160 years after he took his crew of 129 men deep into the Arctic.  

But the men vanished into the frozen Arctic, leaving a few clues but no explanation as to what went wrong.

The first search party set off in 1848 and searches involving teams from Canada, the UK, and the US have continued ever since. Last week, representatives from Parks Canada announced the results from their search this summer, which proved unsuccessful.  

Explorers have found rock cairns with messages from sailors who abandoned ship. They've taken oral history from Inuit people whose ancestors saw the ships get stuck in giant ice floes. In several cases, they've dug up the bones and preserved bodies of the ship's crew. But they've found no ships, no logs, and no sign of Franklin himself.

In subsequent years, a rough sketch of the troubles emerged. During the first winter, the crew disembarked, travelled south to hunt. Franklin left a reassuring message in a rock cairn, signed "All well". A month later, he was dead....