What would be the specific conditions required for a planet to be a more ideal version of Earth?

I want the world to have a much larger proportion of land covered by lush jungle and forest ecosystems with only a very small fraction of the world populated by human-esque people.

It would be in a galaxy with a G star similar to our sun.

Would the conditions be almost identical to earth or are there any subtle or non-subtle improvements that could be made in any of earth's properties (atmosphere, geometry, etc.) that would provide a more suitable world for nature to thrive.

  • $\begingroup$ In this case you quickly received an answer that is very good but in general it is best to wait some time, perhaps a day, before accepting an answer as "The Answer." It is possible that there are other people who had not yet seen your question who could provide a more suitable answer, or perhaps a similar but more detailed answer. $\endgroup$
    – krb
    Jul 24 '19 at 23:41

In astrobiology, this concept is known as the 'Superhabitable Planet'.

Such a planet would be more massive than Earth, up to about 2.5 Earth masses. This additional mass provides shallower oceans, and lower topography. Additionally, it is likely that this feature will be paired with a thicker atmosphere, which distributes the warmth received from insolation more evenly from the equator to the poles.

The star that such a planet orbits would more suitably be a K-class orange dwarf. These stars emit much less UV radiation, and have longer lifespans. Additionally, the habitable zone around such a star doesn't move so much during the lifetime of the star, so over a long timescale, the planet's climate will be more stable.

  • $\begingroup$ Most astrobiologists consider Earth to be on the inside edge of the habitable zone, so I'm not sure a thicker atmosphere at Earth's orbital radius would be a good thing. At Mars' orbit though it'd probably be good. $\endgroup$
    – stix
    Jul 24 '19 at 21:21
  • $\begingroup$ @stix for a dimmer K-class star, this orbit should be good. $\endgroup$
    – Alexander
    Jul 24 '19 at 21:25
  • $\begingroup$ @stix Being more centred in the habitable zone would probably be nice. i.e a touch further out. $\endgroup$ Jul 24 '19 at 21:43
  • $\begingroup$ True. It's also important to keep in mind the habitable zone changes over time. Astrobiologists are still trying to figure out how the Earth could have been in a habitable zone 4 billion years ago when life arose, given how much colder the Sun would have been, and in another few hundred million years, the Sun's output will be too hot for Earth. $\endgroup$
    – stix
    Jul 24 '19 at 21:45
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    $\begingroup$ @M.A.Golding Having done some further reading on the topic, I can only conclude that this is very much an open topic in the field of Exoplanet science. Tackley et al. 2012 (Mantle Dynamics in Super-Earths) suggests that massive planets greater than 2 Earth-masses would in fact have highly convective deep mantles. $\endgroup$ Jul 25 '19 at 23:44

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