Are the Planets Inhabited? — Story, Setting & Ideas

From Lights to Worlds: The Question Reframed

The first chapter establishes the historical pivot: once Earth was seen as a star from afar, the question of inhabited planets became urgent. Maunder does not rush to answer. Instead, he defines inhabited strictly—beings with personality, intelligence, and organic bodies. This narrows the debate, excluding mere vegetation or microbial life. He then traces the nineteenth-century Plurality of Worlds controversy, showing how earlier enthusiasm gave way to skepticism as astronomical instruments improved. The tone is measured, almost judicial, as he prepares to weigh evidence planet by planet.

Thermographs and Frozen Worlds

Maunder’s method is strikingly visual. He constructs thermographs—temperature curves by latitude—for Earth and Mars, then overlays them to highlight differences. For Earth, the mean temperature of 16°C keeps water liquid across most latitudes. For Mars, he adjusts for a thinner atmosphere, longer year, and lack of oceans. The result: Mars is “essentially a frozen planet,” with nightly cold exceeding Earth’s polar extremes. He concludes that any Martian vegetation would need to complete its life cycle in a few daylight hours, surviving each night as spores. The diagram is not decorative; it is the core of his argument.

The Canals of Mars: Observation and Illusion

Maunder devotes two chapters to Mars’s famous canals, a topic then hotly debated. He does not dismiss them outright but examines their reported geometry and seasonal changes. His skepticism is grounded in the limits of telescopic resolution: at forty million miles, linear features can be optical illusions. He cites the American astronomer Newcomb, who calculated that Martian temperatures preclude liquid water on the surface. The canals, if real, would require an engineering feat beyond plausible biology. Maunder’s treatment is a model of how to test a hypothesis against physical constraints.

The Major Planets: Too Cold for Life

Moving beyond the inner solar system, Maunder considers Jupiter, Saturn, and the rest. Their low density, rapid rotation, and frigid upper atmospheres rule out Earth-like life. He speculates on a future when these planets cool, but only to note that even then, conditions would remain inhospitable. The chapter is brief, almost dismissive, as if the evidence against them is so clear that little argument is needed. This structural choice—short shrift for the outer planets—underscores his focus on the more plausible candidates: Mars and Venus.

Maunder’s book is not a survey of possibilities but a narrowing of them. He uses temperature, atmosphere, and water phase as filters, discarding worlds that fail the test. Readers should attend to his diagrams and comparative tables, which carry the argument more than prose alone. The work is a landmark of scientific caution: it asks not what we wish to find, but what the evidence permits.

After all these years, I still find myself musing on how Maunder’s careful weighing of planetary chill and thin air in Are the Planets Inhabited? feels like a quiet prelude to that grander, gentler survey of celestial order, the one I often reshelve nearby: The story of the universe. Volume 1 (of 4) — Context and Discussion. Two old friends, each listening for a distant hum.