Learn Farsi: اولین فضانورد مریخ را کاوش خواهد کرد.

To make the future tense of a compound verb, you put the helper verb khâstan right in the middle! It goes between the noun part (kâvosh, meaning exploration) and the short infinitive of the verb part (kard). So we get kâvosh khâhad kard.

Why do we use khâhad as the helper verb here?

khâhad is the third-person singular present form of khâstan. We use it because the subject of the sentence is avvalin fazâ-navard (the first astronaut), which acts as a third-person (he/she) subject.

Why isn't there an ezafe linking avvalin (first) and fazâ-navard (astronaut)?

In Farsi, ordinal numbers that end in -in, like avvalin, are placed before the noun they describe. When they come before the noun like this, they do not take an ezafe connector.

Why is râ placed right after merrikh (Mars)?

The word râ marks a specific direct object. It tells us what is receiving the action. Since Mars (merrikh) is a specific, named planet being explored, it needs râ right after it.