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Redefining habitable zone for advanced Terran animals
(06-18-2019, 12:38 AM)iancampbell Wrote: Possibly. But there are IMHO two problems with this. One is that the resulting biosphere might generate minor amounts of gases that would be dangerous to Earthly life (the OP mentioned Earthly animals) such as chlorine, ammonia or CO.

The other is that a planet like Earth might be quite rare, in particular the fast spin which largely generates the magnetic field that protects our atmosphere from the solar wind. It's seriously postulated that the rotation of proto-Earth was quite slow, until the Thera event that spun Earth up and created the Moon. After all, of the terrestrial planets only two have reasonably fast spin. And the magnetic fields of Mercury and Venus are negligible. Venus in particular, which is virtually a twin of Earth in most respects, has almost no magnetic field - because it has a rotation period approximately equal to its year.

Just a minor nitpick. A distinction should be drawn between the rotation of the Earth itself, and the rotation of its core. They are strongly related, but not identical... After all, it is known that the inner and outer core rotate in different directions. They are ultimately the source of the Earths magnetic field.

The Earths core is able to rotate in this manner because it is still hot enough to remain liquid. The core of Mars lost too much heat and froze solid eons ago. Like you say, our planets superheated core may be tied to the Theia impact which formed the Earth and Moon.

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RE: Redefining habitable zone for advanced Terran animals - by Avalancheon - 06-18-2019, 06:38 PM

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