The anchoring mechanism was designed over a decade before the lander arrived at its destination. The prevaling theory was that it would encounter a relatively h

The anchoring mechanism was designed over a decade before the lander arrived at its destination. The prevaling theory was that it would encounter a relatively hard and compact layer under a thin dust cover. Then the Deep Impact mission happened while Philae was already in flight and showed that theory to be false. Hindsight is 20/20.