One of the greatest moments of my youth was witnessing the historic 1997 landing of Mars Pathfinder on to the surface of the Red Planet. Unquestionably the “Apollo moment” of my time, akin to the first steps Neil Armstrong took on the moon in 1969, this mission reawakened our space program from its 20-plus year slumber in low Earth orbit towards continuing its role in fulfilling humankind’s destiny as a spacefaring civilization. Later missions to the Red Planet have all followed suit, each one representing a step above the previous one on the ladder of human achievement.
Although the orbiters, landers, and rovers used on these missions have taught us a great deal about Mars, they have also shown that the next big Apollo moment may only come through human exploration of our next-door neighbor in space. Some yearn for a human return to the moon, but repeating yet another lunar mission has not inspired the same level of enthusiasm. One need only to look at the success and media response to the recent book and movie The Martian. The endless stream of books, movies and documentaries all confirm the public’s undying fascination with Mars—something that has been more or less constant since the late 19th century, when Percival Lowell first thought he spotted canals built by Martian engineers. Policy makers should take heed.
In spite of this excitement for Mars, some people suggest a lunar return because the moon is closer and thus much easier and safer to reach. However, investing in the lengthier, riskier journey to the Red Planet would be more than compensated for by a vastly more engaged public and likely greater scientific return. In the 1960s, the intense rivalry between the U.S. and former U.S.S.R. was a major factor in John F. Kennedy’s dramatic commitment to reaching the moon, but scientists and the public weren’t thinking of geopolitics as astronauts made one step after another until Armstrong took that “one giant leap for mankind.” The politics have changed, but Mars is a far more rewarding target, both philosophically and scientifically, than the moon ever was. So let’s challenge ourselves and go there next.
Arguably, the notion that life may have once existed on the Red Planet is the most compelling scientific reason to send investigators there. The ancient Martian rocks reveal a very different world in the distant past—one with a thicker and warmer atmosphere and perhaps even an Earth-like climate, seas and precipitation. This has been inferred from the widespread evidence of fluvial features on the surface first mapped by Mariner 9. Such intriguing results motivated the Viking missions of the 1970s to search for potential life with Martian soils, which yielded ambiguous results.
However, NASA’s Curiosity rover recently confirmed the presence of surface organics and seasonal releases of methane. There is even evidence for a subsurface lake at Mars’s south pole. Thus, the prospect that Mars may possess life, even today, has never been better—and several rover missions dedicated to finding it are already in the pipeline. However, robots will never be as clever, flexible and creative as people are. Even should these missions unambiguously discover life, humans will still be needed on the scene to properly assess its nature and history on the Red Planet.
Moreover, because Mars likely had a more Earth-like climate in the past, Martian rocks could tell us a lot about our planet. The moon never had plate tectonics. In contrast, ancient terrains on Mars record magnetic stripes—similar to those found on our ocean floor—construed to be possible evidence for past plate tectonics, a process that has only been found on Earth and is associated with its long-term habitability. A growing body of evidence also suggests that volcanism and meteoritic impacts each could have triggered hydrothermal systems within the Martian crust. These hydrothermal systems, which include heat and fluids within rock, could have provided habitats for the origin of life on both Earth and Mars. Such Martian life could still be preserved as fossils within rocks in the same way that extinct life on Earth is.
For a while in 1996, it even appeared that we’d found it. Even as Mars Pathfinder launch preparations were under way, scientists announced they’d found evidence of fossilized Martian bacteria within a chunk of rock, known as ALH84001, that had been blasted off the surface of Mars by an asteroid impact and eventually fell to Earth as a meteorite in Antarctica. Subsequent analyses could not prove that the “fossils” inside the rock were anything more than mineral formations. Nevertheless, public and scientific interest in this meteorite was very high, contributing to the rising popularity of astrobiology, the search for and (eventual) study of life in the cosmos. Human exploration of the Red Planet, together with the search for life there, have both remained—and will continue to be—central goals of the NASA Astrobiology Roadmap.
Also notable is the fact that Mars hosts two tiny moons, Phobos and Deimos, potato-shaped bodies that may be important to understanding how planets form and even how they may become habitable. It is possible that one (or both) may be a piece of Mars that was blasted into orbit by an incoming asteroid. Another notion is that at least one of them could have been an asteroid itself, captured by Mars billions of years ago. Scientists think that asteroids that may have helped supply the Earth with water; the exploration of Phobos and Deimos could help confirm that theory. Indeed, Japan’s Martian Moons Exploration (MMX) program, slated to launch in 2024, will be the first robotic sample return mission to Phobos. Such a mission could pave the way for human exploration of these moons.
All of this helps make the case for sending astronauts to Mars. A lunar return is neither novel nor particularly challenging. Indeed, fascination with the moon started waning even before the final Apollo mission in 1972; several subsequent missions were canceled. This is not to say that we should never return to the moon, but Mars should be given clear priority in a time where budgetary and political constraints make the sustainability of long-term programs a perennial issue. Concerns about the dangers of such a mission ignore humankind’s uncanny ability to overcome challenges once taken to the limit.
Although sending humans to Mars would be more expensive than sending them to the moon, the returns—both technological and scientific—would be correspondingly greater as well. Even should we eventually find that life does not exist on the planet, we would have gained a much better understanding of life’s limits and the conditions that make a planet habitable. Such information is vital for comprehending our own origins and the potential habitability of exoplanets. It is time to set our sights towards landing humans on Mars because that will trigger the next Apollo moment, perhaps culminating in the discovery of life outside of our own pale blue dot.