This is the 3688th most frequent Portuguese word.
vasta
Extensive; vast.
Here, 'vasta' is used as an adjective meaning 'extensive' or 'large in scope', modifying 'coleção' (collection).
A biblioteca possui uma vasta coleção de livros.
The library has a vast collection of books.
'Vastas' is used here in its plural form to describe the extensive scope of 'possibilidades' (possibilities).
O cientista explorou as vastas possibilidades do experimento.
The scientist explored the vast possibilities of the experiment.
In this context, 'vasta' describes the considerable extent or breadth of the 'experiência' (experience).