Rosetta mission lands Philae probe on the tail of a comet . It has taken two years for the ESA - 2 probe to rendezvous with its tail . Scientists weigh in on why this is a monumental event for humanity .
Rosetta mission lands Philae probe on the surface of a comet . It has taken 10 years for the ESA-led spacecraft to rendezvous with its target . Experts weigh in on why this is a monumental achievement for humanity .