Second Most Earth-Like Planet to Date Found

[radtech497]

Such...awesome...crunchy...math...

Radtech, some of that mass range gets into the "lots of internal heat and surface vulcanism ranges." What ranges of density and mass give the most Earth-like surface conditions for a 6-billion year old star and planet?

The most obvious (and flippant) answer is 5515 kg/m^3 and 5.9736e+24 kg, which describes Earth. But I'm pretty sure you are referring to Kepler-452b and not just any planet. From this paper, the lowest mass and density figures give a planet that is 0.77 times as tectonically active as present-day Earth; the high end of the mass range gives a world that is 1.22 times as tectonically active. The crust is noticeably thinner than is Earth's (0.89x to 0.38x). With a mantle mass ranging between 2.025 and 4.725 Earth-masses, the mantle temperatures are very similar (between 2273 and 2323 K at its current age of 6.0 Gyr). So it is likely that surface conditions on Kepler-452b are, geologically at least, fairly similar to those found on Earth throughout the mass range. The constituents of the atmosphere, of course, is largely dependent on volcanic outgassing (most, if not all, of the planet's primary atmosphere of hydrogen and helium will long ago have been lost to space), though the Earth-like insolation implies a nitrogen-dominant atmosphere (if photosynthetic life is present, there may be a significant O2 fraction; if not, CO2 levels may be significant enough to induce a "runaway greenhouse" similar to what happened on Venus). If the planet has been dessicated a`la Venus, then it is likely that the planet is in a "stagnant-lid mode" in which tectonism has ceased and volcanism is restricted to periodic (several million years or more between events) lava flows which resurface significant portions of the surface, rather than discrete eruptions. So it really depends on whether life has emerged on Kepler-452b.

Hope this helps,

Radtech497