Exploring Habitable Zones: Searching for Life Beyond Earth

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Discussion Overview

The discussion centers around the concept of habitable zones in the solar system, particularly in light of recent findings of water on Mars and other celestial bodies. Participants explore the implications of these findings for the potential existence of life beyond Earth, considering both theoretical and practical aspects of habitability.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that the discovery of water on Mars and other bodies may expand the definition of the habitable zone.
  • It is noted that the habitable zone is traditionally defined as the distance from a star where liquid water can exist, but water ice is prevalent in the outer solar system.
  • One participant argues that basic lifeforms can survive in environments without liquid water, implying that life could exist at the edges of the liquid water range or beyond.
  • There is uncertainty regarding the historical presence of liquid water on Mars, with some suggesting that water may have existed only under specific atmospheric conditions.
  • Another point raised is the potential for liquid water beneath the icy surfaces of Jupiter's moons, supported by tidal heating.
  • Participants express skepticism about the evidence for liquid water on Mars, citing alternative explanations for Martian geological formations that resemble those formed by water on Earth.
  • The search for life on Mars is often justified by the possibility of liquid water, with expectations that any life found would likely be microbial.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the extent of the habitable zone or the historical presence of liquid water on Mars, with multiple competing views and ongoing uncertainty present in the discussion.

Contextual Notes

There are limitations regarding the assumptions made about the conditions necessary for life and the definitions of habitability, as well as unresolved questions about the geological history of Mars and the nature of water in the outer solar system.

cstoos
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With the confirmation of water on at least two other major bodies in our solar system so far (Mars, Moon), has this expanded the range of the "habitable zone" when searching for locations of possible life in the solar system?
 
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The habitable zone is the range of distances from a sun where water is liquid.
water ice is present pretty much everywhere in the outer solar system - comets for instance are mostly ice
 
Right, but we know that liquid water once flowed on Mars, correct?

There are also basic lifeform that survive in environments without water in it's liquid form so it seems to me that life could exist on the limits of the liquid water range...or even slightly past.

http://serc.carleton.edu/microbelife/extreme/withoutwater/
 
cstoos said:
Right, but we know that liquid water once flowed on Mars, correct?
Not sure if that's totally accepted, water could have flowed as ice or as a hydrate, if there was liquid water it would only have existed while Mars had a much thicker atmosphere.

A bigger argument for a wider habitable zone is probably the moons of Jupiter, they can have liquid water ,below an ice covered surface, with the heat provided by tidal forces from jupiter.
 
cstoos said:
Right, but we know that liquid water once flowed on Mars, correct?
From what I can gather, there's still a fair amount of uncertainty where this is concerned. See this blog post, for instance:
http://blogs.discovermagazine.com/b...5/are-martian-gullies-formed-by-water-or-not/

As near as I can tell, the evidence for liquid water on Mars largely consists of evidence from formations that we see on Mars that look very similar to formations on Earth which are, on Earth, formed only with water. However, as this paper shows, it is conceivable that other processes are producing these formations on Mars instead.

Regardless, the possibility of liquid water on Mars is one significant reason why probes we send there frequently look for life. We expect that if there is life on Mars, it would consist of a few hardy microbes.
 

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