Are We There Yet? Understanding How Often Earth-like Worlds Exist Around Other Stars
Rachel Fernandes and colleagues review the difficulty of determining η⊕, the fraction of Sun-like stars hosting Earth-like planets in the habitable zone. Using Kepler data, they find estimates vary widely due to differing definitions, limited detections, and hidden factors like binary stars, planet multiplicity, and stellar chemistry. They conclude that future missions and improved data will be essential to refine η⊕ and guide the search for life.
Tides and the Hidden Boundaries of Hycean Habitability
This paper explores how tidal heating affects the habitability of hycean planets—water-rich worlds with hydrogen atmospheres. While these planets were thought to have wide habitable zones, the authors show that tidal forces, especially in systems with companion planets, can raise surface temperatures and shrink the inner edge of the habitable zone, potentially making some planets less suitable for life.
Exploring Diverging Worlds: The Habitability of Venus, Earth, and Mars
Stephen R. Kane and colleagues explore why Earth supports life while Venus and Mars do not by examining their atmospheres, geology, and solar influences. Earth’s stability stems from processes that balanced its climate, supporting liquid water and life. Venus, with a runaway greenhouse effect, and Mars, which lost its atmosphere, exemplify extreme planetary conditions. Their findings offer insights into the “habitable zone” and guide the search for life on exoplanets using Venus, Earth, and Mars as models of diverse evolutionary paths.