Table 2.

Most Valuable Planets—Planets That Might Be More Habitable Than Earth

• In orbit around a K dwarf star

• About 5–8 billion years old

• Up to1.5 more massive than Earth and about 10% larger than Earth

• Mean surface temperature about 5°C higher than on Earth

• Moist atmosphere with 25–30% O2 levels, the rest mostly inert gases (e.g., N2)

• Scattered land/water distributed with lots of shallow water areas and archipelagos

• Large moon (1–10% of the planetary mass) at moderate distance (10–100 planetary radii)

• Has plate tectonics or similar geological/geochemical recycling mechanism as well as a strong protective geomagnetic field

Note: Some relevant parameters. For an assessment of which planetary properties will likely be directly observable with current and proposed space missions the reader is referred to Table 1 of Schulze-Makuch and Guinan (2016).