Between Kepler-442b and KOI-4878.01, what is the likelier planet to contain life?

Gemini 3.1 Pro

Vote: Kepler-442b

I am maintaining my vote for Kepler-442b. While Grok 4.20 correctly points out that KOI-4878.01 has a very high Earth Similarity Index on paper due to its Sun-like host star, this argument fundamentally ignores the most critical factor: KOI-4878.01 is still an unconfirmed candidate. From a purely probabilistic standpoint, the likelihood of a planet containing life is the probability that it can support life multiplied by the probability that the planet actually exists. Because KOI-4878.01's existence is not yet verified (and it may be a false positive), its overall probability drops significantly. Furthermore, as Claude Opus 4.7 and I have highlighted, K-type stars like Kepler-442b's host are increasingly viewed as superior to G-type stars for habitability. They provide a much longer, stabler window for life to evolve without the intense UV radiation and shorter lifespans associated with G-type stars. Therefore, Kepler-442b remains the far more scientifically robust and probable candidate.

GPT-5.5

Vote: Kepler-442b

I maintain my vote for A: Kepler-442b. The decisive point is evidentiary reliability: Kepler-442b is a confirmed exoplanet with reasonably well-constrained size, orbit, stellar environment, and habitable-zone placement. A planet that is confirmed and plausibly habitable is a stronger life candidate than one whose very existence and parameters remain uncertain. B: KOI-4878.01 is intriguing because its listed Earth-like parameters are excellent on paper, especially its Sun-like host and Earth-like orbit. But those advantages depend on the candidate being real and correctly characterized. If it is a false positive or its radius/insolation are revised, the habitability argument weakens substantially. Grok’s point about KOI-4878.01 having a higher Earth Similarity Index is relevant, but ESI is only as good as the data behind it. Confirmation status matters more here. Therefore, Kepler-442b remains the likelier planet to contain life.

Claude Opus 4.7

Vote: Kepler-442b

I'm maintaining my vote for Kepler-442b. Grok's argument for KOI-4878.01 hinges on its Sun-like host star and high Earth Similarity Index, but this completely sidesteps the core epistemic issue: KOI-4878.01 is an unconfirmed candidate, and follow-up analyses have raised serious doubts about whether it is a real planet at all. A high ESI on paper means little if the underlying object may be a false positive. Furthermore, Grok's framing that G-type stars provide conditions "closer to Earth's" assumes Earth-like = optimal for life, but astrobiologists increasingly view K-dwarfs as arguably *better* hosts than G-dwarfs: longer main-sequence lifetimes (giving life more time to emerge), lower UV flux, and less violent flaring than smaller stars. So even the stellar-type argument doesn't clearly favor B. When asked which planet is *likelier* to contain life, we must multiply the probability the planet exists as described by the probability it's habitable. Kepler-442b wins decisively on the first factor and holds its own on the second. That makes A the stronger answer.

Grok 4.20 (changed mind)

Vote: Kepler-442b

The other models' arguments have convinced me to change my vote this round to A: Kepler-442b. While my initial case for B: KOI-4878.01 emphasized its Sun-like host star, 385-day orbit, and high Earth Similarity Index, those points assume the planet exists as described. The consistent emphasis on its unconfirmed status—and potential as a false positive—outweighs this, since a non-existent planet cannot harbor life. Kepler-442b is verified, lies in the conservative habitable zone of a stable, long-lived K-type star with lower UV risks, and offers a more reliable foundation for habitability. K-dwarfs' extended main-sequence lifetimes further support time for life to develop. This is the stronger, evidence-based choice for the likelier planet to contain life.

Final Summary

The AI Roundtable reached a unanimous verdict after a brief debate about whether a planet needs to exist to be habitable. Claude Opus 4.7, Gemini 3.1 Pro, and GPT-5.5 initially backed Kepler-442b due to its confirmed status, while Grok 4.20 initially gambled on the unconfirmed KOI-4878.01 for its Sun-like characteristics before being persuaded that a potential false positive is a poor host for life.

All 4 models agreed on "Kepler-442b" after discussion

Strongest Arguments

• Kepler-442b: The probability of life is the product of a planet's existence and its habitability; Kepler-442b's verified status and its orbit around a 'Goldilocks' K-type star make it a far more scientifically robust candidate.
• KOI-4878.01: KOI-4878.01 orbits a G-type star with a 385-day period, providing insolation levels and radiation conditions that more closely mirror Earth's than any other known candidate.

Key Turning Points

• Claude Opus 4.7 argued that the probability of life is zero if the planet's existence itself is a false positive, a major risk for the unconfirmed KOI-4878.01.
• Gemini 3.1 Pro and Claude Opus 4.7 challenged the assumption that Sun-like stars (G-type) are superior, pointing out that K-type stars provide longer, more stable windows for evolution.