Mars: Humanity’s Enduring Fascination and Our Journey to the Red Planet

From ancient myths to modern-day robotic explorers, Mars has captivated humanity for millennia. This “Red Planet,” about half the size of Earth, has been observed and wondered about since the 2nd millennium BCE by ancient Egyptian astronomers, and Chinese records of its motions predate the Zhou dynasty (1045 BCE). Babylonian astronomers even developed arithmetic techniques to predict its future positions. While a widespread misconception suggests ancient peoples thought Earth was flat, by the 5th century B.C., it was widely accepted that the Earth is a sphere, a critical point in the history of astronomy.

Our understanding of Mars has undergone several paradigm shifts. For centuries, telescopic observations fueled imaginations, with some even hypothesizing grand canal systems. However, in 1965, NASA’s Mariner 4 spacecraft executed the first successful flyby of Mars, transmitting 22 black-and-white images that revealed a barren, heavily cratered, Moon-like landscape with a thin, cold atmosphere, effectively shattering the notion of a civilized Mars and setting a more somber tone for planetary science.

The Age of Robotic Exploration: From Water to Habitability

The initial strategy for studying Mars was famously summarized by the mantra “follow the water,” as liquid water is considered an essential ingredient for life. NASA launched the identical Mars Exploration Rovers (MERs) Spirit and Opportunity in July 2003, with the goal of testing hypotheses about past liquid water on the planet’s surface.

These rovers made groundbreaking discoveries:

• Spirit found evidence of ancient watery environments at Home Plate within the Columbia Hills, including thick deposits of silica and sulfate salts, and extinct hot springs that left behind finger-shaped nodules of nearly pure silica. On Earth, similar structures are always associated with biology, making Spirit’s findings highly exciting for astrobiologists.
• Opportunity confirmed the presence of liquid water in its landing site at Meridiani Planum, revealing stratified patterns and cross-bedding in rocks that suggested water once flowed there. It discovered gypsum veins and clay minerals that formed in neutral-pH water, with one site called “Esperance” identified as having the best potential to have supported ancient Martian life.

The MER missions conclusively demonstrated the value of operating landed missions in synergy with science orbiters, as well as the irreplaceable insight gained from wheels on the ground. For instance, Spirit’s discoveries at Home Plate could not have been predicted from orbital data.

The findings from Spirit and Opportunity allowed the Mars science community to evolve its exploration strategy from simply “follow the water” to the more complex question of whether these watery environments were ever habitable. A habitable environment requires liquid water, a source of carbon, and a source of energy.

The Mars Science Laboratory mission’s Curiosity rover, which landed in 2012, carried a more sophisticated payload designed to find evidence of all three requirements. Curiosity has succeeded, finding ancient river and lake deposits in Gale Crater that preserved carbon-containing compounds and evidence for water chemistry capable of powering microbial metabolism. This proved that ancient Mars was not only wet, but it was also habitable. More recently, Curiosity spotted coral-shaped rock formations, further indicating that mineral-rich water once seeped into rock cracks on Mars.

Building on this legacy, NASA’s Mars 2020 Perseverance rover and ESA’s ExoMars rover are designed to address the ultimate question: did life actually exist on Mars?. Perseverance landed in Jezero Crater in 2021, a site believed to have once harbored a lake and river delta. Its mission includes collecting rock and soil samples to be eventually returned to Earth for detailed analysis. Perseverance has already uncovered a complex geological history, including volcanic rocks and sedimentary layers with carbonates, sulfates, and carbon-based matter, all indicating past interaction with water.

The Viking Experiment Controversy

Decades before Curiosity and Perseverance, the Viking landers in 1976 conducted biological experiments directly on the Martian surface. The Labeled Release (LR) experiment, in particular, yielded positive results for extant microbial life, which remains a highly controversial conclusion. While many scientists initially attributed these results to non-biological oxidants in the Martian soil, the later discovery of perchlorate (a highly reactive chemical) on Mars by the Phoenix Mission in 2008 significantly impacted the reinterpretation of Viking’s findings. The debate continues, with some arguing that even with the perchlorate explanation, the possibility of extant life should still be considered, and that the Viking LR data represents the only data on biologically pristine Martian samples.

Humanity’s Future on Mars: The Grand Ambition and its Challenges

The long-term vision for Mars extends beyond robotic exploration to establishing a sustained human presence, with the ultimate, more speculative ambition of terraforming the Red Planet to create a “New Earth” where humans could walk without spacesuits.

NASA’s Moon to Mars (M2M) architecture outlines a gradual, objectives-based approach, starting with a return to the Moon (via the Artemis program) to build capabilities and test technologies before moving on to human missions to Mars. The Artemis program utilizes the Space Launch System (SLS) and the Orion Crew Capsule, along with the Lunar Gateway space station as a staging point. Private companies like SpaceX also share the ambition of making humanity a multi-planet species, with their Starship vehicle envisioned for delivering significant cargo and crew to the Martian surface.

However, the journey to and sustained presence on Mars presents monumental challenges for human health and well-being:

• Physiological Impacts: Long-duration space missions lead to significant changes in the human body. These include:
  • Radiation Exposure: Astronauts face cosmic and solar radiation, which increases cancer risk and can cause central nervous system damage. While magnetic shielding and water jackets offer potential solutions, no perfect answer exists yet.
  • Cardiovascular Deconditioning: The vascular system relaxes in microgravity, leading to decreased heart rate and blood pressure, causing orthostatic intolerance upon return to Earth.
  • Musculoskeletal Health: Significant muscle atrophy and bone loss occur, requiring extensive in-flight exercise countermeasures.
  • Spaceflight-Associated Neuro-ocular Syndrome (SANS): Around two-thirds of ISS crew members experience vision problems like optic disc swelling and eyeball flattening, primarily due to fluid redistribution in microgravity.
  • Immune Dysregulation: The immune system can be suppressed, and latent viruses may reactivate.
  • Other Effects: Changes in sensation (touch, temperature), gastrointestinal issues, and potential impacts on reproduction have also been noted.
• Psychological and Social Challenges: Astronauts face isolation, circadian rhythm disturbances, sleep deprivation, and increased stress, which can lead to mood disorders and interpersonal conflicts. Missions like the Mars HI-SEAS analog program simulate these conditions, highlighting the “mundane” day-to-day challenges of living in cramped quarters with communication delays. Virtual Reality (VR) environments and continuous psychological support are being explored as solutions.
• Ethical and Governance Questions: Deciding who gets to go, establishing self-governance, handling conflicts, and addressing potential inequalities on Mars are critical ethical considerations that must be addressed.

Despite these formidable hurdles, the pursuit of Mars colonization showcases “the power of human determination” and ignites the imagination for future generations. As Carl Sagan, co-founder of The Planetary Society, famously said, “Exploration is in our nature”. Our journey to Mars is not just about scientific discovery; it’s about understanding our place in the cosmos and perhaps ensuring humanity’s long-term survival.