So Far Yet So Close

For the first settlers, the sunrise on the first morning would look unusually faint — a distant sun peeking over a dusty horizon. Breakfast would consist of shelf-stable foods, perhaps some freeze-dried fruit, and a fresh plant or two, grown throughout the long journey. Walking around the habitat, the travelers would feel out of sorts, their bodies buoyant, unmoored in this slighter gravity, and fatigued from the long journey that would have already exposed them to numerous risks: loss of muscle mass and performance, high levels of radiation and the psychological pitfalls of a lengthy, confined expedition.

Yet with great risk comes great reward. When they pull on their spacesuits, unlock the hatch and step outside, they would be greeted by a terrain no human has walked upon before: the cold, dusty, rocky landscape of the red planet.

It’s not an exaggeration to say that sending humans to Mars would be one of the greatest feats of human ingenuity ever. It is perhaps even the inevitable next step in our desire to explore. For decades, scientists and engineers have been preparing for the journey. Now human missions finally seem on the horizon: NASA hopes to send astronauts to Mars in the 2030s, and SpaceX hopes to go even sooner, by 2026. 

Ensuring humans can survive together on a small spacecraft and then thrive on an unforgiving planet still requires much more work. NASA has outlined several specific hazards that astronauts will face, including microgravity, social isolation and confinement, and hostile or closed environments, which include small spacecraft and habitats that must keep astronauts safe and healthy. Each inspires its own set of threats. 

Yet outer space has a way of inspiring good work. Northwestern researchers, students and alumni are part of a global undertaking aimed at both understanding and mitigating such hazards. Though they will likely never visit the red planet, they are helping to pave the way for those who will.

HAZARD: Hostile or closed environments, including small spacecraft and habitats

Keeping the crew alive and thriving during the flight is only the first part of the challenge. When humans land on Mars, they will disembark to find a cold, rocky landscape rife with dust storms and radiation from outer space, knowing that this is the place they will call home for months or even years to come.

Such isolation and self-reliance have been common challenges in voyages throughout most of human history. Explorer Ernest Shackleton wrote that his ill-fated trip across Antarctica that began in 1914 was full of “high adventure, strenuous days, lonely nights, unique experiences and, above all, records of unflinching determination, supreme loyalty and generous self-sacrifice.”

But in our hyperconnected, constructed world, it can be difficult to imagine such a dangerous, remote existence, or how such a landscape would affect the very team meant to study it. 

A depiction of the envisioned 3D-printing process to form the habitat’s protective shell. Credit: Martian 3Design by Northwestern Team

That’s what Mars analog missions are for. Brian Shiro ’00, an aspiring astronaut, has been a pseudo-Martian several times, including at the Flashline Mars Arctic Research Station on Canada’s Devon Island, the Mars Desert Research Station in Utah and the NASA-funded Hawaii Space Exploration Analog and Simulation (HI-SEAS).

At these analog sites, the crew lives and works under constraints similar to those they would face on Mars. Days are filled with performing extravehicular activities, running research projects, writing research reports to mission support, and doing chores such as habitat maintenance and cooking meals. The rules are strict: No going outside without wearing a spacesuit, no real-time communication with Earth, no browsing the internet, no more than five minutes of shower time per week. And anything that breaks must be fixed with available tools and materials.

Shiro, a geologist who studied volcanoes in Hawaii for his doctorate, was co-investigator from 2013 to 2018 at the HI-SEAS site, where he trained crews to navigate rocky landscapes in their spacesuits and collect geological data. He also studied the effects of isolation on teamwork and crew performance in harsh environments.

Shiro applied to be an astronaut multiple times and was among a group of highly qualified top applicants. Though he was not selected, he still holds out hope for private space travel.

Living on Mars, he says, “the goal would be to keep everyone alive and working well together, to make sure crews stay sane, happy and healthy.” 

But to create a livable community on Mars, astronauts would need shelter — ideally one that was ready for them when they landed. NASA has said that it could send 3D-printing robots to Mars to build shelters in advance of human arrival, but what materials they would use remains an open question. 

“You cannot ship cement bags from Home Depot to Mars,” says Gianluca Cusatis, professor of civil and environmental engineering at McCormick.

Several years ago, Cusatis and his graduate student Matthew Troemner developed an answer to the Mars construction problem: Marscrete, a concrete made from a Martian soil simulant and sulfur, which is abundant on the planet. 

Marscrete was a success: It is two to three times stronger than Earth-based sulfur concrete, and it reacts with the metals in the Martian soil, making the material as strong as the concrete used to build skyscrapers on Earth (typically made of gravel, cement and water). That’s important, because the planet faces several meteorological and astronomical hazards, from dust storms to radiation to meteor strikes.

A Northwestern team’s Martian habitat design for NASA’s 3D-Printed Habitat Challenge. Credit: Martian 3Design by Northwestern Team

In 2018, Troemner, Cusatis and other team members put Marscrete to the test when they designed a Martian habitat as an entry into NASA’s 3D-Printed Habitat Challenge. The igloo-like structure includes a lab, kitchen, bathroom and private bedrooms and takes into account Martian gravity and the planet’s shifting sand dunes.

They knew they had a strong enough design to withstand the climate, but to make the design human-friendly, they consulted with professors from across the University. Turek, an expert on circadian rhythms, suggested a design that would help maintain astronauts’ sleep-wake cycles during a Martian solar day, which is 24 hours and 39 minutes. That led the team to include hue-changing lights that shine cooler colors during the day and more reddish tones in the evening. They also included monitors that showed a video feed of the area outside — a pseudo-window to the Martian day.

The design won fifth place in the Level 1 Virtual Design Challenge. The next step was to build the shelter. To do so, they designed a 3D printer and created a specialized 3D-printing facility on campus capable of printing Marscrete. 

Though they did not advance in the NASA challenge, the team plans to use the facility for concrete research, both with sulfur and other earthly materials. “There’s a lot of interest in large-scale 3D printing of concrete,” Troemner says. “It opens the door to new kinds of concrete structures.”