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Andy Weir's bestselling story "" predicts that by 2035 NASA will have landed humans on Mars three times, perfected return-to-Earth flight systems and collaborated with the China National Space Administration. We are now 10 years past the and 10 years shy of its fictional timeline. At this midpoint, Mars exploration looks a bit different than how it was portrayed in "The Martian," with both more discoveries and more controversy.

As a who works with NASA missions to study Mars, I follow exploration science and policy closely. In 2010, the set goals for human missions to Mars in the 2030s. But in 2017, the shifted NASA's focus toward returning first to the moon under what would become the .

Although for crewed missions to Mars have gained popularity, for landing humans on Mars remain fragile. Notably, over the last 10 years, it has been robotic, rather than crewed, missions that have propelled discovery and the human imagination forward.

Robotic discoveries

Since 2015, satellites and rovers have reshaped scientists' understanding of Mars. They have revealed countless insights into how its climate has changed over time.

As Earth's neighbor, climate shifts on Mars also reflect solar system processes affecting Earth at a time when life was first taking hold. Thus, Mars has become a focal point for investigating the age-old questions of "" and ""

The Opportunity, Curiosity and Perseverance rovers have driven dozens of miles studying layered rock formations that serve as a record of Mars' past. By studying sedimentary layers—rock formations stacked like layers of a cake—planetary geologists have pieced together a vivid tale of environmental change that dwarfs what Earth is currently experiencing.

Mars was once a world of erupting volcanoes, glaciers, lakes and flowing rivers—an environment not unlike early Earth. Then its core cooled, its magnetic field faltered and its atmosphere drifted away. The planet's exposed surface has retained signs of those processes ever since in the form of landscape patterns, sequences of layered sediment and mineral mixtures.

Arabia Terra

One focus of scientific investigation over the last 10 years is particularly relevant to the setting of "The Martian" but fails to receive mention in the story. To reach his best chance of survival, protagonist Mark Watney, played by Matt Damon, must cross a vast, dusty and crater-pocked region of Mars known as .

In and , I, along with colleagues at Northern Arizona University and Johns Hopkins University, published detailed analyses of the layered materials there using imagery from the and satellites.

By using infrared imagery and measuring the dimensions of surface features, we linked multiple, layered deposits to the same episodes of formation and learned more about the widespread crumbling nature of the terrain seen there today. Because water tends to cement rock tightly together, that loose material indicates that around 3.5 billion years ago, that area had a drying climate.

To make the discussions about this area easier, we even worked with the to name a few previously unnamed craters that were mentioned in the story. For example, one that Watney would have driven right by is now named , after a town in Ukraine.

More to explore

Despite rapid advances in Mars science, many unknowns remain. Scientists still aren't sure of the precise ages, atmospheric conditions and possible signatures of life associated with each of the different rock types observed on the surface.

For instance, the Perseverance rover recently a unique set of rocks hosting organic—that is, carbon-based—compounds. Organic compounds serve as the building blocks of life, but more detailed analysis is required to determine whether these specific rocks once hosted microbial life.

The in-development mission aims to address these basic outstanding questions by delivering the first-ever unaltered fragments of another world to Earth. The Perseverance rover is already caching rock and soil samples, including ones hosting organic compounds, in sealed tubes. A future lander will then need to pick up and launch the caches back to Earth.

Once home, researchers can examine these materials with instruments orders of magnitude more sensitive than anything that could be flown on a spacecraft. Scientists stand to learn far more about the habitability, geologic history and presence of any signs of life on Mars through the sample return campaign than by sending humans to the surface.

This perspective is why NASA, the European Space Agency and others have invested some US$30 billion in robotic Mars exploration since the 1960s. The payoff has been staggering: That work has triggered in robotics, telecommunications and materials science. For example, Mars mission technology has led to better and .

It has also of NASA and the U.S. as bastions of modern exploration and technology; and it has of students to take an interest in scientific fields.

Calling the red planet home?

Colonizing Mars has a seductive appeal. It's hard not to cheer for the indomitable human spirit while watching Watney battle dust storms, oxygen shortages and food scarcity over 140 million miles from rescue.

Much of the momentum toward colonizing Mars is now tied to SpaceX and its CEO Elon Musk, whose stated mission to make humanity a "" has become a sort of rallying cry. But while Mars colonization is romantic on paper, it is extremely difficult to actually carry out, and many critics have of a Mars habitation as a refuge far from Earth.

Now, with to its science budget, the U.S. risks dissolving its planetary science and robotic operations portfolio altogether, including sample return.

Nonetheless, for human space exploration to somehow continue to progress, despite those proposed cuts—effectively sidelining the robotic, science-driven programs that have underpinned all of Mars exploration to date.

Yet, it is these programs that have yielded humanity's richest insights into the red planet and given both scientists and storytellers like Andy Weir the foundation to imagine what it must be like to stand on Mars' surface at all.

This article is republished from under a Creative Commons license. Read the .