The flight bans came amid fears that the ash - a mixture of glass, sand and rock particles - can seriously damage aircraft engines.

BBC: EU emergency talks called on volcanic ash air chaos

But perhaps more importantly, there is the huge reputational damage for a bank that used to be seen as a rock of probity and stability.

BBC: UBS: How big will the Libor bill be?

Not wanting to damage the holes themselves, they used a chisel to chip away rock samples from a chimney-like tunnel that connects two of the depressions.

WSJ: NY teacher delves into mystery of 'Indian Ovens'

Scientists need to be sure that when the big hammer tool turns in a rock it breaks the surface into a useable powder that will not clog or damage the sample handling mechanism.

BBC: Curiosity Mars rover deploys its rock brush

"The removal of the graffiti may well damage some of the very small, fine, holds that exist on the boulders and on the rock", Dave Gibson explains.

BBC: Glasgow & West Scotland