What does it mean to “look it”?

Question

What does the emphasized part of the following excerpt mean? It's from an edition of 2001: A Space Odyssey.

She had been assembled in orbit around the Earth, tested on a translunar maiden flight, and finally checked out in orbit above the Moon. She was a creature of pure space -- and she looked it.

Answer 1

It is qualifying the preceding statement. It is saying that the ship is not only a "creature of pure space", but that it looks as though it is a creature of pure space.

This phrase is quite common (emphasis is mine):

He was most fifty, and he looked it. His hair was long and tangled and greasy, and hung down, and you could see his eyes shining through like he was behind vines. It was all black, no gray; so was his long, mixed-up whiskers.
(From The Adventures of Huckleberry Finn by Mark Twain)

He was sick, he said, and he looked it.
(From Tom Sawyer by Mark Twain)

At this point, the door opened, and Mr. Bucket walked into the room. He was cold and tired, and he looked it. All day long, he had been working in the streets.
(From Charlie and The Chocolate Factory by Roald Dahl)

He was a pedant, to the most extreme point, the greatest pedant I had met on earth, and with that had a vanity only befitting Alexander of Macedon. He was in love with every button on his coat, every nail on his fingers--absolutely in love with them, and he looked it!
(From Notes From the Underground by Fyodor Dostoevsky)

I love this one. The sentence invokes an image of the man being so overly proud of appearance!

Answer 2

The it, in your example, refers to the state of being a creature of pure space.

looked it, in this instance, is used to give emphasis to the the previous observation.

He was completely exhausted from traveling across the desert for eight days, and he looked it.

The emphasis relies on the idea that looks can be deceiving. So someone could be a creature of pure space and yet not look it.

For example, the Emperor of Japan in the mid to late 19th century lived in a great palace and was dressed in the finest silks, waited on hand a foot, etc. He looked like a descendant of the Sun Goddess.

Saigo Takamori, on the other hand, was a politician and military officer of some renown and high standing, but he did not look it. In fact it has been reported on one occasion that when he left the Emperor's palace that he was arrested because he looked of such lowly standing the guard did not believe he could have any business being in the palace.