As scientists push the boundaries of space exploration, they are not only seeking Earth-like planets but are now considering that even better candidates for habitability may exist. Could other planets offer conditions superior to our own? Has such an exoplanet been found?
Scientists on Better Planets
In 2020, an article titled In Search of a Planet Better than Earth: Top Contenders for a Superhabitable World was published in Astrobiology, a scientific journal. The authors, Dirk Schulze-Makuch, René Heller, and Edward Guinan, argue that disregarding the possibility of ‘superhabitable’ planets reflects anthropocentrism and ‘geocentrism,’ which they suggest contradicts the Copernican Principle.1
In the article, they clarify that ‘habitable planets’ are not necessarily planets where life currently exists. Rather, they refer to planets with conditions that could, under the right circumstances, support the development of life. Such a planet would orbit a compatible star and have the right temperature, atmosphere with sufficient oxygen (O₂), suitable gravity, and other essential factors. A ‘superhabitable’ planet, therefore, would offer conditions even more conducive to life than those on Earth.
Selection Criteria
Schulze-Makuch and his colleagues identified 24 celestial objects as planets that could possess characteristics more favorable than those of Earth. Their study focused on exoplanets observed through the transit method in the Kepler Space Telescope mission, categorized as Kepler Objects of Interest (KOI). Prior to this analysis, they developed a set of criteria to identify such planets, paying special attention to attributes of the host stars and the planets themselves.
Stars
The scientists argue that a planet suitable for habitation, and potentially even more hospitable than Earth, must orbit a certain type of star. They considered main-sequence stars, which are categorised by mass and temperature into types O, B, A, F, G, K, and M. Type O stars are the hottest and most massive, while Type M stars are the coolest and least massive. Despite their lower mass and temperature, Type M stars are the most prevalent, making up over 75% of all stars in the universe. By contrast, our Sun is a Type G star, with characteristics that lie between these two extremes in terms of mass and temperature.
The authors of the article contend that type O, B, A, and F stars, which consume their fuel rapidly, exist for only tens or hundreds of millions of years—too briefly to sustain life-supporting conditions. Notably, they also view type G stars, such as our Sun, as only moderately suitable for life. Type M stars, while abundant, are very cool,2 meaning their habitable zones lie extremely close to the star. This proximity poses additional challenges for sustaining life, including potential tidal locking and exposure to intense solar flares. Consequently, the scientists consider type K stars the most favourable, followed by type G stars, and claim that these stars should be at least 4.6 billion years old.
Planets
To focus on potentially habitable planets, the group of scientists excluded those located outside their star’s habitable zone, thereby ruling out planets that were either too close or too distant from their stars. Additional criteria included:
- A mass up to 1.5 times that of Earth and approximately 10% larger in size,
- An estimated age of 5 to 8 billion years (according to evolutionary models),
- An average planetary temperature approximately 5ºC warmer than Earth’s,
- A moist atmosphere with 25-30% oxygen (O₂), accompanied by neutral gases such as nitrogen (N₂),
- A suitable ratio of surface water to land,
- A large moon at an optimal distance,
- Evidence of tectonic activity or similar geological processes,
- The presence of a strong magnetic field.
Limitations in Finding Habitable Planets
Among the 24 identified planets, very few fulfill all the conditions deemed essential for supporting life, and considerable gaps remain in our knowledge about each one. Only one candidate, KOI 5715.01, meets all three essential criteria: it orbits a compatible type of star, is of a suitable age, and is situated at an optimal distance to maintain temperatures that could support habitability. However, uncertainties persist regarding whether this planet possesses a sufficiently stable greenhouse effect to support life.3
There are additional issues to consider. Of the 24 planets, only two have been confirmed: Kepler-1126 b (KOI 2162) and Kepler-69c (KOI 172.02). This means that the existence of the remaining 22 planets, including KOI 5715.01, remains unverified; they are still classified as planet candidates and may not exist at all. Furthermore, the two confirmed planets are located too far away for current instruments to study them in detail.4
Missing Data
In short, when it comes to finding planets that might be better than Earth, we are still at the starting line. First of all, almost all of these 24 planets are just candidates, meaning their existence still needs to be confirmed. Second, the only things we know about them (if they even exist) are their distances from their stars and their sizes. Key factors crucial for supporting life—factors that might depend on these two known characteristics—are still a mystery.5
Moreover, the authors themselves acknowledge that the ‘age’ of host stars is derived from highly uncertain data and should be regarded as estimations only.6 Another issue lies with the transit method, which can reveal a planet’s size but not its mass—an essential parameter that requires further studies.7 While the article claims that dozens of potentially ‘superhabitable’ planets have been identified, this conclusion seems somewhat premature. No such planet has yet been confirmed.
Earth Remains Unique
Is it possible that planets more suitable for life than Earth exist? This question remains difficult to answer. To date, scientists have confirmed over 4,000 exoplanets, including 166 rocky planets of a similar size to Earth,8 yet none of them has been found to be habitable. While there is hope among some researchers of discovering a planet with conditions matching or even surpassing those on Earth, the rigorous criteria for habitability make this prospect extremely unlikely.
Earth is the only known planet with conditions exceptionally well-suited for sustaining life.9 Since God formed our planet among countless others, it is clear that Earth was created with a special purpose: to be our home. The Holy Scriptures confirm this, highlighting Earth’s unique position in the vastness of the universe.
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Footnotes
- Schultze-Makuch, D., Bains, W., and Irwin, L.N., 2020. In search for a planet better than Earth: top contenders for a superhabitable world. Astrobiology, 20(12), pp.1394-1404. Available at: https://www.liebertpub.com/doi/pdf/10.1089/ast.2019.2161.
- ‘Habitable zone or Goldilocks zone’. This refers to the space around a star where a planet could maintain surface temperatures suitable for life.
- Schultze-Makuch, D., Bains, W., and Irwin, L.N., op. cit., pp.1399-1402.
- Ibid., p.1399.
- Faulkner, D.R., 2020. Superhabitable planets. Answers in Genesis, 21 October. Available at: https://answersingenesis.org/astronomy/superhabitable-planets/.
- Schultze-Makuch, D., Bains, W., and Irwin, L.N., op. cit., p.1401.
- Ibid., p.1402.
- NASA, 2021. Terrestrial planets. Exoplanet Exploration: Planets Beyond our Solar System. Available at: https://exoplanets.nasa.gov/what-is-an-exoplanet/planet-types/terrestrial/.
- Faulkner, D.R., op. cit.
- The Bible, New King James Version, 1982, Isaiah 45:18.
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