There are often evolutionary parallels on the different worlds because creation tends to be economical.

Part of what drives us to explore and discover is the intangible: expanding our horizons, feeding our curiosity, finding all those unexpected things, and trying to answer those profound questions discussed in previous chapters, like how did the universe begin? How did life begin? Are we alone?

While human spaceflight is certainly compelling – and it has always been a big part of my reporting career -- there is something about unmanned robotic spacecraft that has always tugged at my heart. These machines are our emissaries out into the cosmos, flung to faraway places that humans can’t yet visit. I grew up hearing about spacecraft like Mariner, Viking and Voyager boldly going on some of the first-ever deep space missions and making monumental discoveries that changed our view of the Solar System. They showed us worlds we previously could only dream about and artists could only imagine.

A blade of grass is a commonplace on Earth; it would be a miracle on Mars. Our descendants on Mars will know the value of a patch of green. And if a blade of grass is priceless, what is the value of a human being?

so important to the future of space exploration and space travel.

It’s pretty hard to get to another star system. Alpha Centauri is four light years away, so if you go at 10 per cent of the speed of light, it’s going to take you 40 years, and that’s assuming you can instantly reach that speed, which isn’t going to be the case. You have to accelerate. You have to build up to 20 or 30 per cent and then slow down, assuming you want to stay at Alpha Centauri and not go zipping past. It’s just hard. With current life spans, you need generational ships. You need antimatter drives, because that’s the most mass-efficient. It’s doable, but it’s super slow.