How to get to Mars

So said Carl Sagan, the beloved astronomer and presenter who did so much to explain and popularize humankind's attempts to explore space. Shortly before his death in 1996 he recorded a message, including the above, for future Mars explorers – and his soundfile reached the Red Planet on the Phoenix lander in May 2008. 

Since then, NASA's Curiosity and Perseverance rovers have explored Mars, with China's Tianwen-1 hoping to touch down in May 2021. But what are the chances of getting boots on the ground, with humans scuffing up the red dust? To do that, we will need to overcome some significant challenges. 

Then there's radiation from the sun. "On Mars, you're not protected with a big magnetic field or a strong atmosphere like we have here on Earth," says Hutty – and this affects tech as well as humans. "You get lots of false positives in your code, bit flips and things like that that we have to watch out for, detect and correct for before they do any damage to the signals that we're transmitting."

But radiation does, of course, affect humans, and really quite badly. Mark McCaughrean, senior science advisor at the ESA, goes so far as to say it's "probably the biggest problem that we face going on long duration trips."

He notes that while astronauts serving six to 12 months on the International Space Station receive "maybe 30 or 40 times" the radiation at ground level, they are still protected by the earth's magnetic field. 

"But as soon as you go above the Van Allen belts, which trap radiation and the magnetic field blocks radiation, you're completely exposed. You can mitigate against that by going at a time when the sun is not very active – the 'solar minimum' – but the sun can have an eruption and chuck out a whole bunch of high-energy particles. So on your way to Mars, you need a 'lifeboat' or shelter on board, a place to go and hide if a solar storm passes over you."

The relative orbits of the planets means there's no turning back once you've hit your radiation limit: "The way the planets line up, you will have to stay on Mars for quite a while, for a year and a half or so, and then come back in another half-year journey."

That's a quarter of a decade in space absorbing ionizing radiation – "very high energy radiation, breaks the DNA down" – which "is enough to raise your chances of contracting fatal cancer by more than five percent. 

"And that's the limit that we set on these things: We try to mitigate against sending our astronauts to Mars and then having them come back with cancer. So we really need to work hard on these shelters to minimize the radiation we absorb."

This season's fashions in spacesuit design largely tend toward the 'keeping you alive' end of the scale, as Robert Wild explains. He's what's known as an 'analog astronaut,' suiting up for tests in some of Earth's most inhospitable conditions, such as deserts.

"The reflective coating helps keep the heat load down – if you have a lot of sun, you don't want to heat up too quickly," he says at the Austrian Space Forum in Innsbruck, while being laboriously fitted into a suit in a process that takes three hours ("With a really fast and trained team, it can be a little bit faster.").

What look like supports on the outside of his legs are actually designed to make his life harder – for the purposes of verisimilitude. "When you're in a real spacesuit in an area of low pressure on the outside, you have air pressure on the inside so you can breathe, and that makes the suit balloon out," he explains. 

"That means that whenever you move, you're pulling against this balloon that restricts your movement. And that's what we have here in order to simulate that restriction. This is actually pulling my leg straight, just like it would be in a real spacesuit."

Wild's boss at the Austrian Space Forum, Gernot Groemer, is busy finessing the "second generation of spacesuits," a leap forward which he says is "like comparing a Ford Model T with an electric car." And that new breed of suit, the Serenity, could do away with that sci-fi favourite, the airlock – something which could cause problems with the surface dust on Mars.

"It is what we call a reentry suit, which means you don't need an airlock anymore," says Groemer. "You attach the suit to the wall of a spacecraft; you step in from behind with an open life-support backpack; you close the backpack, you decouple and you're outside."

Before we pack our spacesuitcase, let's ask a simple question. Should we go to Mars at all? Never a man shy of an opinion, Elon Musk thinks there will be a million humans there by the 2060s, but not everybody is convinced that it's the destination of choice. 

"I think there's a lot of science fiction dreaming going on, there's a lot of wish fulfilment," says the ESA's Mark McCaughrean. "Anybody who says they want to go and live on Mars should go and spend six months in Antarctica and then six months in the Atacama Desert, but take away all the oxygen that you have, take away most of the water you have, and then live underground in those places because there's no protection from radiation on Mars."

That's not quite what is says in the brochure, but that's another thing: McCaughrean says that going to Mars wouldn't be so much a vacation as relocation – remember that minimum quarter-decade trip length: "You're not going to be zipping backwards and forwards, you're going to go there and live in a small box in a deeply inhospitable place."

McCaughrean is also suspicious of treating Mars as a Plan B if we ruin this planet. "This is just utter nonsense," he insists: "Almost nothing we can do to the Earth that will make it less hospitable than Mars will ever be. When people talk about it in terms of hope and dreaming and inspiration, I think this could apply to saving the environment here on the Earth."

Over at the International Space University, Chris Welch cautiously disagrees. "I'm a big fan of human spaceflight," he says. "Elon Musk and I don't share many attributes, but he and I both agree that it's not a good idea for all the humans to live on one world: If anything happens to this planet, then it's 'Thank you and good night' for humanity. 

"As a matter of longer-term species survival, I think it's an excellent idea if people live on space stations, live on the moon, live on Mars, live on asteroids and anywhere in the solar system – although it's going to take us a while to get there."

But who decides which of us go where? That's what worries Janet D Stemwedel, a professor of philosophy at San Jose State University whose work focuses on science and ethics. 

"If we decide that putting humans on Mars might make sense, then we have to think: Which humans?" she asks. "Is this in anticipation of bringing all the earthlings to Mars because we somehow used up this planet in a really unfortunate way? 

"My guess is probably that's not what the folks who are hot to colonize Mars have in mind, which means we need to have a discussion about why we think it's OK to take some people to this brave new frontier and leave a whole mess of people here to deal with how we didn't do as well with the planet we started with."

Stemwedel also notes a warning from history: "Missions of colonization are going to enrich some people and leave other people worse off." For her, this is not a question of science but ethics: "The thing we really need to do is to figure out how better to share a world with each other."

That's certainly a sentiment that would ring true for Sagan, the stargazing dreamer with whom our story began. It's worth revisiting his hopeful message to future Martin explorers.  

"I don't know why you're on Mars," he said. "Maybe you're there because we recognize that if there are human communities on many worlds, the chances of us being rendered extinct by some catastrophe on one world is much worse. Or maybe we're on Mars because of the magnificent science that can be done there; the gates of the Wonder World are opening in our time. 

"Or maybe we're on Mars because we come, after all, from hunter-gatherers and for 99.9 percent of our tenure on Earth, we've been wanderers. And the next place to wander to is Mars. But whatever the reason you're on Mars is, I'm glad you're there. And I wish I was with you."