Aw, thanks!

Many astronomers, even at the time, doubted his observations, but the question wasn't finally resolved until the 1960s, so I was taught that Mars was covered with canals and then a little later, discovered it wasn't.

Humanity's whole view of space exploration was wildly simplistic at the time. Everyone expected a Moon base almost immediately, Mars colonies not long after that, and that we'd all be floating around in our own personal space vehicles going to the moon for weekends right about now.

At some point about 10 years ago, I tried to estimate what it would cost to actually set up a self sustaining colony on Mars. It was insanely expensive, between one and thirty quadrillion dollars, the output of our whole planet for a decade or more.

There are two issues. The first one is that every single industrial process that humans participate in takes for granted unlimited quantities of free air and very large quantities of very cheap water, and neither of these are true on Mars - and all our agriculture also takes advantage of above-freezing temperatures and a lot of light from the Sun, which you also don't have on Mars.

The second is that the environment of Mars is implacably hostile to human life. Mars is a dark, cold, airless, arid, lifeless, radioactive, poisonous desert with frequent high-energy dust storms made up of that poisonous dust.