For billions of years the planet had been devoid of anything that might be considered complex life. But then the machines arrived. 

At first they didn't stay. Either scooting past the outer atmosphere without entering orbit, or careening to the surface to a thoroughly destructive end.

But pretty quickly they began to persist. First in orbit and then later on the dusty global continent. Eventually several arrived that had mobility, crawling their way across a few small areas; probing, evaluating, and streaming data to their orbital companions.

An astute observer would ask themselves what's coming next. The machines have clearly evolved, and it might only be a matter of time before they begin to self-repair, even self-replicate in-situ rather than from wherever they've come.

I am, of course, describing the planet Mars. 

But I'm not just trying to be cute in describing our history of Mars exploration this way. We still struggle with some outstanding questions at the hairy edge of speculation and extrapolation to do with how machines might explore the universe on a grander scale, and what that might really look like. For instance, it may be that sending biology between the stars is next to impossible, but sending autonomous, self-replicating machines is a way for any sentient species to explore and expand their reach.

How does this begin though? And what would a machine-settled world look like?

Mars could well be our first good experiment to address precisely these questions. It harbors quite the machine collection today. Even Mariner 9 - the first mission to successfully orbit Mars, back in 1971 - is still there. And will be there until around 2022 when it is expected to finally succumb to atmospheric drag and burn up or crash onto the surface.

In fact, although they're not all tracked still, there might be as many as 14 robotic craft currently orbiting Mars. And in terms of machines on the surface, either crashed, once functional, or currently functional, the tally is around 17.

One of the next arrivals will be NASA's Mars 2020 rover. 

This machine got a 10-hour test drive recently in a clean room at NASA's Jet Propulsion Laboratory. It is an impressive piece of hardware. Similar to the Curiosity rover, but also very much an evolved piece of robotics.

In the images below, and especially the video, I'd suggest you also take a look at the humans. While we know that their bowing, kneeling postures are really in order to keep an eye on the rover's movements and workings, it's hard not to imagine that there is a certain amount of supplication. After all, for a while this machine will be at the very top of the evolutionary chain on a distant world.

The machine: Mars 2020 rover. Credit: NASA and JPL-Caltech

Credit: NASA and JPL-Caltech