View Full Version : Habitable zone

2009-Apr-10, 03:34 PM
Hi, I was reading about the habitable zone on Wikipedia (see http://en.wikipedia.org/wiki/Habitable_zone ) and I was wondering why the properties of a planet is not taken in account in the determination of a habitable zone.

For instance, if Mars (which according to the article lies beyond the habitable zone) would have been the size of Earth (necessary to sustain a meaningful atmosphere), and have a significant magnetic field, surely it would qualify for a possible place where life could thrive? The same may hold true for Venus.

My question is: within our Solar System, what range between the Sun(0 AU) and Pluto (~40AU) *could* be a habitable zone (for plant life at least) for a planet similar to Earth?


Wizard From Oz
2009-Apr-10, 04:01 PM
In very loose terms the habitable zone is anywhere water can exist in liquid form. After you establish that, then the properties of the planet become imporant. Really at this stage it is really only a thought exercise because we really lack data points.

But from researchers point of view it gives them a guide of where to direct their studies. Example if we find a system with 10 planets in the inhabital zone, they will concentrate their efforts more than in a system that say only has one planet.

Fiery Phoenix
2009-Apr-10, 07:12 PM
Theoretically, if a planet receives sufficient solar energy, has a reasonable atmosphere, and possesses water in its liquid state then life as we know it should be there, or at least in its simplest forms. Generally speaking, those three requirements are only satisfied within the habitable zone. And of course, the habitable zone of a system is directly determined by the type of the parent star and its basic physical properties.

Since this is essentially a theory, I don't think it's that necessary to consider the planets' properties, although it's an interesting idea.

2009-Apr-10, 08:32 PM
As mentioned, the HZ is just a beginning parameter to look for. But both its definition as well as your point of earth-like planets make the assumption that no type of life cannot begin or thrive outside of those limits. We have yet to either confirm that either way, but as we find more examples of life here on earth that exist in what the rest of the biosphere considers inhospitable conditions, our constraint that defines what is and isn't habitable to ANY life broadens.

It's the same problem faced by the Drake equation and its partners. We only have one variable we have some idea on, the rest are just educated guesses that may or may not be wrong.