In “The Martian,” the film based on Andy Weir’s bestselling novel that hit theatres Friday, Matt Damon plays an astronaut stranded on Mars.
From the extreme cold to the deadly radiation, there are many traits about Mars that make it inhospitable.
Here are some of the main obstacles to surviving — and colonizing — the fourth rock from the sun.
Getting to Mars ain't cheap. NASA's current Mars mission concept would set us back about $50 billion over the course of a decade, or about twice as much as the moon program cost between 1962 and 1972. Mars Society president Robert Zubrin think it can be done for cheaper, but it would still be between $5 and $20 billion.
Spaceflight is inherently risky. Even if something doesn't go wrong during launch or landing, the life support systems on the ship could fail at any time during the 9 months it takes to get to Mars. And that's not to mention the intense radiation and reduced gravity you'd be subjected to.
Even if we raise enough money and survive the harsh conditions of deep-space travel, getting to the surface of Mars is no easy task. Right now, no technology exists that could land humans safely on the surface. The largest thing we've ever landed there is roughly the size of a car.
Once we're on the Red Planet, we'd have to deal with the fact that it's freezing. The average temperature is minus 81 degrees Fahrenheit. While a summer day near the equator can reach 70 degrees, it can plunge to nearly minus 200 degrees in winter near the poles.
Mars' atmosphere is extremely thin, and contains just 0.15% oxygen (compared to 21% on Earth) -- not nearly enough to breathe. Most of the atmosphere (96%) is carbon dioxide.
Mars' thin atmosphere is less efficient at shielding the surface from harmful radiation, like UV light from the sun and high-energy cosmic rays. This radiation can severely damage plant and animal cells, and can even be fatal.
Agriculture could be a major problem on Mars if the Martian soil isn't fertile. You need the right balance of bacteria and chemicals to grow plants on Earth, and as far as we know, the Martian soil is devoid of all life -- including bacteria.
Mars receives between 1/3 to half the amount of sunlight as Earth, depending on where it is in orbit around the sun. With less sunlight, solar-powered instruments take longer to charge and farming could prove tricky.
Plus, there's the fact that they'd need water, which is essential for life as we know it. Mars was once home to vast oceans, but today it mostly exists in the form of ice at Mars' poles (and, we now know, in occasional salty flows on its surface).
Also, Mars is frequently plagued by dust storms that last for a few days and carry tiny dust particles at speeds of 33 to 66 mph. On rare occasions, the storms are big enough to cover the entire planet for several weeks.
In addition to surviving the tough external conditions, the first people to travel to the Red Planet will likely have to contend with feelings of isolation and loneliness unlike any they've ever encountered.
And when it comes to talking to your friends back on Earth, you'd have to deal with this: On average, Mars is 12.5 light-minutes from our home planet. That means it would take at least 25 minutes to have a conversation with someone on Earth. In other words, if something went wrong, you're on your own.
Besides the mental challenges, our bodies could suffer too. On Mars, you'd weigh 1/3 of what you weigh on Earth, which could have unforeseen health consequences. Our muscles evolved under Earth's gravity, but with lower gravity it's possible that we could lose muscle mass, similar to how astronauts do under zero gravity.
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