The red planet Mars, named for the Roman god of war, has long been an omen in the night sky. And in its own way, the planet’s rusty red surface tells a story of destruction. Billions of years ago, the fourth planet from the sun could have been mistaken for Earth’s smaller twin, with liquid water on its surface—and maybe even life.
Now, the world is a cold, barren desert with few signs of liquid water. But after decades of study using orbiters, landers, and rovers, scientists have revealed Mars as a dynamic, windblown landscape that could—just maybe—harbor microbial life beneath its rusty surface even today.
Longer year and shifting seasons
With a radius of 2,106 miles, Mars is the seventh-largest planet in our solar system and about half the diameter of Earth. Its surface gravity is 37.5 percent of Earth’s.
Mars rotates on its axis every 24.6 Earth hours, defining the length of a Martian day, which is called a sol (short for “solar day”). Mars’s axis of rotation is tilted 25.2 degrees relative to the plane of the planet’s orbit around the sun, which helps give Mars seasons similar to those on Earth. Whichever hemisphere is tilted closer to the sun experiences spring and summer, while the hemisphere tilted away gets fall and winter. At two specific moments each year—called the equinoxes—both hemispheres receive equal illumination.
But for several reasons, seasons on Mars are different from those on Earth. For one, Mars is on average about 50 percent farther from the sun than Earth is, with an average orbital distance of 142 million miles. This means that it takes Mars longer to complete a single orbit, stretching out its year and the lengths of its seasons. On Mars, a year lasts 669.6 sols, or 687 Earth days, and an individual season can last up to 194 sols, or just over 199 Earth days.
Traveling to Mars is just the first leg of the journey — when Earth and Mars are closest to each other, the trip will take a mere 260 days. Once we get there, the challenge becomes landing on the planet’s surface. What type of landing system will get our astronauts and colonists safely to the surface?
Back in 2007, scientists considered four possible solutions to get astronauts to the surface. One idea was a Legged Landing System based off the Lunar Lander. This system could provide the option to both land and take off from the red planet. Secondly, the SLS System, or Sky-Crane Landing System, would use population systems to lower rovers and other equipment onto the surface. This system can unload cargo and take off again. The third design discussed was an Airbag Landing System, which would rely on a rocket that cuts its thrust above the surface of the planet, as well as an airbag for the equipment to land on. However, this wouldn’t be the best option for people. Lastly, scientists considered Touchdown Sensing. Equipment senses the surface and the landing site, and compensates accordingly.
Ten years later, scientists have other ideas on how to land manned missions to Mars. According to Richard (Rick) McGuire Davis, Jr., Assistant Director for Science and Exploration and co-leader of the Mars Human Landing Sites Study at NASA, “landers will have to dive deep into the Martian atmosphere and skirt closer to the surface than we have done in the past… [since] the Martian atmosphere is the thickest near the surface.” When asked about the previous methods of technology mentioned above, he said, “The lander is so heavy that many technologies will not work, such as airbags, sky-cranes and parachutes. In fact, to slow down, we will be heavily reliant on jets.” How heavy will the crewed missions be? This supersonic retro-propulsion technology is required to be able to deliver the “projected 20 metric ton” spacecraft to the surface of Mars. For comparison, the Curiosity rover was only 1 metric ton.
NASA is already considering what kind of habitation we’ll need to survive on the surface of Mars. Six companies began designing possible habitat prototypes in 2016, with completed prototypes expected in 24 months.
All these habitats will likely have a few things in common — they have to be self-sustaining, sealed against the thin atmosphere, and capable of supporting life for extended periods without support from Earth. To get an idea for what to expect, think about the ISS. “The International Space Station has really taught us a tremendous amount of what is needed in a deep space habitat,” said Davis. “We’ll need things like environmental control and life support systems (ECL SS), power systems, docking ports, [and] air locks so that crew can perform space walks to repair things that break or to add new capabilities.” Expect big, robust equipment to travel across the stars to Mars during the first manned mission. Whatever the astronauts use must be up for the long journey.
Davis also posed an interesting question: how much space is needed for each crew member? Could you imagine spending months in one location, surrounded by the same walls day in and day out? How far apart would they have to be to keep claustrophobia at bay? “In the days of the Space Shuttle, missions ran for 7-15 days, and there was not a lot of space for each crew member. In a space station, where crew members are onboard for a much longer time (typically 6 months), we have found that crew members simply need more space.” Based on this logic, it’s possible that habitable bases on Mars will require more square footage for inhabitants.
Science fiction also does a great job helping the public imagine what this future mission will look like. The recent film, The Martian, portrayed the kind of habitats NASA is investigating for a Mars. Nine pieces of technology showcased in the movie are accurate to the kind of equipment astronauts on the planet will use.
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