Well I pointed to one already: the numbskulls in charge of space programs can't even return us to our closest neighbour (about 400,000km) so thinking they can get us to Mars in the foreseeable future (an average of 225,000,000km, so about 550× the distance) is ludicrous.

At the rate things are going we won't be standing on the Moon again by the end of a purported Trump term, not to mention Mars, just based on distance alone.

But this isn't even what I'm actually talking about. I'm talking about how badly people underestimate the difficulties of a trip to Mars. Here are some (and only some!) of the issues:

1. We have never sustained human beings in a closed environment for the length of time a trip to Mars would take (nine months or so). This is the absolute basic first step. To send people to Mars they have to reach Mars alive, and … despite many experiments and tests we don't know how to do this. We're trying to climb K2 and we haven't even taken the first step out of our beds yet. This isn't something we're going to suddenly solve. Can we solve it? Sure. Almost certainly. But not in four years. Probably not in forty years.
2. Mars is the "Killer Planet" when it comes to our technology. More probes have been lost to Mars than to any other planet by number, and only Venus beats it for proportion. (I'm now laughing as I picture people downvoting me because I'm suggesting that colonizing Venus is even dumber than colonizing Mars!) The problem of landing on Mars is hard for machinery that's a whole lot tougher than a human body is. It will take way more than four years (and likely forty) to figure out how to safely get people down to the planet once their space coffins arrive.
3. Why space coffins? Radiation is a killer! The Apollo astronauts received about the equivalent of two head CT scans of radiation in their ~6-day round trip. Extrapolating that to a 540-day round trip and you've got the equivalent of about 180 head CT scans. This is bad with a capital B. (Don't believe me? Go to your local hospital and stick your head in the CT machine and trigger it 180 times. Come back and report on the results.) "But," I can hear you say, "most of the radiation the Apollo astronauts received came from the Van Allen belts." This is true. And that's because the Apollo missions were sent out in periods of solar activity minima. (And even with that planning they had a scare in one of the missions!) There are no 18-month periods of solar minima. For 540 days our astronauts will be bathing in solar wind, flares, CMEs, cosmic rays, and a whole lot more sources of ionizing radiation. But hey, at least we might get someone cool like Reed Richards or Susan Storm out the other end, right?
4. OK, so we've solved keeping people in a closed habitat, we've solved the landing thing within sane risk levels, and we have invented magic anti-radiation technology. Have we invented a substitute for food? No? Well then, provisioning is going to be a huge problem. Here on Earth we eat 1.5-2kg of food per day. So let's assume that for this trip we've turned that food into the densest (and most monotonous) form possible and make it 0.5kg instead. That's 270kg of food per person at an absolute minimum with no margin for accident or error. Realistically that's closer to a ton per person if we don't want a single accident to turn our spaceship into a fancy space coffin. Now add water to that. That's 3l per day, or another 1.5 tons per person for the trip as a razor's edge minimum. OK, I'll be nice and pretend we invent some fancy waste reclamation system that's 90% efficient, and I'll ignore that we get a lot of our water from our food and we really need to account for the bone-dry rations here. That's still 150kg per person without a safety margin and more likely about half a ton per person. Add oxygen to that (and again I'll stick to a fiction that says we can realistically use a pure-oxygen environment) and that's about a kilogram per day, so half a ton per person, or, with safety margins about 1.5 tons. And so on and so on and so on. We lack the ability to launch that much into orbit, complete with the spacecraft systems around it, plus the squishy fleshy things that need it, in four years. We just don't have enough rockets. And this is for the simplest mission profile.
5. And as for colonizing it once we overcome those difficulties (not likely within your lifetime, remember!): https://defector.com/neither-elon-musk-nor-anybody-else-will-ever-colonize-mars Living on Mars is just a non-starter from the get-go. It's far harsher than the harshest environment we have ready access to here on Earth (Antarctica) and we barely even have a foothold on Antarctica which is literally a million times easier to get to and provision.

There's also one more reason to be certain that getting to Mars is not going to happen anytime soon and that colonizing Mars is a pipe dream that will literally never happen: going back to the topic of this board, the Apartheid Manchild is soundly convinced it's just around the corner. Like his Hyperloop. And his full self-driving. And his solar panel factories. And his … you get the picture. The fact that this twat, of all people, is the biggest cheerleader of visiting and colonizing Mars should tell you just how implausible the idea really is.

P.S. Keep downvoting the truth away, children. It won't change the fact that if you're alive now you will almost definitely not see any kind of semi-permanent human presence on Mars and you likely won't even see a human landing on Mars. "Click-click-clickety-click" doesn't change harsh reality. You can't vote reality away!)

Let's fire coffins into the sky!

Your parents lied to you. You're not funny.

Probably not even within the next five decades. Possibly not even within the next ten.