Learn Portuguese (Portugal): Nós exploraremos o espaço no próximo ano.

This is the future indicative of the regular verb explorar (to explore). To form the future tense for regular verbs, you do not chop off the ending. Instead, you take the entire infinitive (explorar) and add the future endings directly to it. For nós (we), the ending is -emos, giving us explorar + -emos = exploraremos.

Why is there an o before espaço if the English translation is just "space"?

In Portuguese, definite articles like o and a are almost always required before broad, general concepts, abstract ideas, or unique entities like outer space. While in English you just say "We will explore space", Portuguese grammar requires you to say "We will explore the space" (o espaço).

Why do we use no in no próximo ano for "next year"?

The word no is a contraction of the preposition em (in) and the masculine definite article o (the). When talking about things happening in a specific year, month, or week, Portuguese generally uses the preposition em. So, em + o gives us no, making the phrase literally translate to "in the next year".

Doesn't the adjective usually go after the noun? Why is it instead of ?