Learn Dutch: Astronauten lopen niet op de maan zonder hun jas. - Astronauts do not walk on the moon without their coat.

In Dutch, niet usually comes after the main verb, but it is placed before phrases that start with a preposition (like op, in, or naar) to describe a place. Since op de maan (on the moon) tells us where the action happens, niet goes right in front of it.

Why do we use niet instead of geen here?

We use geen when we want to say "no" or "not a" directly in front of a noun. In this sentence, we are negating the action of the verb lopen (they do not walk), so we must use niet.

Could niet go at the very end of this sentence?

No, that would sound incorrect. While niet sometimes goes at the end of short sentences, it gets pushed earlier when there are extra details. It needs to come before prepositional phrases like op de maan (on the moon) and zonder hun jas (without their coat).

Why does the sentence say hun jas (their coat) in the singular when there are multiple astronauts?

In Dutch, when a group of people each have one of an item, it is very common to use the singular form. Since each astronaut wears one coat, Dutch speakers say hun jas rather than the plural hun jassen.