key to earth like planets is in the moons

[notFritzArgelander]

https://phys.org/news/2021-09-earthlike ... moons.html

[Bigzmey]

It may actually work. One do need Earth like system with moon relatively large to produce enough wobble.

[notFritzArgelander]

It may actually work. One do need Earth like system with moon relatively large to produce enough wobble.

Yes, it's the controlled non chaotic wobble that is good for life conditions. Mars wobbles chaotically, most ungood.

[SparWeb]

I don't know if you share this opinion, but my own belief has been growing for some time that the Moon - and originally the Theia impact that created it - is the essential starting point for Earth's unique geology, and the sustenance of life. Without the stability of the rotation and the daily tidal stress cycle, the structure of the earth's crust would be so different that it could be as hostile as Venus or barren as Mars here. Even if it could have started, as suggested for both Mars and Venus, it's obvious that they can't support life now. The most obvious thing they lack is a substantial Moon, and the tectonic activity that is absent (or really different in the case of Venus) leaves little chance for life to form, let alone to thrive.

I don't think there really is a general consensus on this in the scientific community, but maybe it's going in that direction.

Another way to put it, we may be closing on some new terms that belong in the DRAKE equation. The probability of life (intelligent or otherwise) on any planet is dependent on certain factors in its creation and properties of the planet itself. It may be worth adding a factor that considers the chance of having a suitable Moon, doing its part for making life possible, and sustaining it for many billions of years.

With any luck, these planet surveys will offer some clue about the prevalence and distribution of moons around terrestrial-size planets. Then we'll have a chance to estimate the value for that new term in the Drake Equation.

The vice-versa condition may actually be more common, where the suitable geology and activity is more often found on a moon of a larger gas giant. Again a system with substantial tides offering the prospect of plate tectonics, volcanism, crustal recycling, renewal of surface materials, etc needed to keep things like soil, atmosphere, oceans, precipitation and, ultimately, life going.

[notFritzArgelander]

I think that we are largely in agreement. The only point on which we may differ is on the acceptability od Drake equation approaches. I think that the Drake equation is too crude and naive to be useful. Rather the formation and distribution of formation of types of planets should be treated as a statistical dynamics problem, not just a multiplication.

Here is one very fine study that I rather admire which aims in this direction.

https://academic.oup.com/mnras/article/ ... 11/1046202

See section 4.2 for a critique of the Drake methodology. This doesn't yet include the geophysics of a large moon and atmosphere regeneration via active plate tectonics....

[SparWeb]

Their method skips those details entirely.

Instead of a "bottom-up" calculation of all combined conditions, these authors use observed phenomena (which may be refined in the 6 years since) to make statistical approximations. There are assumptions just as difficult to prove in their method, but it closes the margin of uncertainty much narrower with very few assumptions, and the result isn't very sensitive to some of them.

Fascinating. THANKS AGAIN

[GCoyote]

I'm also in agreement here Steve and I followed essentially the same lines of reasoning as those you have laid out above.

Calling other planets "Earth-like" is IMHO very premature as we cannot yet see exoplanets at a level of detail that makes such comparisons meaningful.

[notFritzArgelander]

I'm also in agreement here Steve and I followed essentially the same lines of reasoning as those you have laid out above.

Calling other planets "Earth-like" is IMHO very premature as we cannot yet see exoplanets at a level of detail that makes such comparisons meaningful.

Yes. Earth sized is not earth like. For instance , Venus.