It's impossible to say definitively what the Moon looked like a billion years ago, but we can make some educated guesses based on what we know about its formation and evolution.

Here's what we know:

* The Moon formed early: The prevailing theory is that the Moon formed about 4.5 billion years ago, shortly after Earth itself. This means that it was very young a billion years ago.

* The Moon was once hotter: In its early years, the Moon was much hotter than it is now. This was due to the heat generated by its formation and from radioactive decay within its interior.

* Volcanic activity: Early on, the Moon experienced a period of intense volcanism. This activity resulted in vast lava flows that reshaped its surface, creating features like the dark, smooth maria.

* Cratering: The Moon has been bombarded by asteroids and meteoroids throughout its history, which left craters on its surface. These craters were more numerous and prominent in the early days when the solar system was still full of debris.

So, what did the Moon look like a billion years ago?

* It likely had a more active surface: The volcanic activity may have been more intense, resulting in more lava flows and visible volcanic features.

* It likely had a different surface texture: The Moon's surface was likely smoother and less heavily cratered than it is today, since the intense bombardment would have slowed down significantly over time.

* Its color may have been different: The Moon's surface color could have been slightly darker due to the presence of more fresh volcanic material.

However, without direct observations from that time, we can only speculate. Future missions to the Moon, with advanced instruments, might help us learn more about its ancient appearance.