on the other hand, D looks pretty good for an “ammonia world”:

http://graywyvern.livejournal.com/tag/gliese+581+c

m.

Sounds like areasonable model youve come up & not going toargue tehe numbers - my maths ability is,alas, lamentable.

But doesn’t it all depend on the atmospheric composition? Water and CO-2 are both good greenhouse gases but what if the planets atmosphere is helium-lithium or methane / nitroen or suchlike exotic mix? Clouds can both reflect and absorb, cool and heat - we find Pluto’s atmosphere makes it colder and Venus’es (& Earth’s) much hotter than it otherwise would be.

Plus do we really know what the basic nature of the planet is whether its a rocky super-Earth, outsized old SF idea of Planetary Ocean Venus (eg. as imagined in Isaac Asimov’s Lucky Starr &the Oceans of Venus’) or some sort of warmed -up pygnmy exoNeptune.

Where exactly is the line between gas / ice Giants like Neptune and Super_Earths -is it 5-Earth masses -or 7? Or ten? Or three? (After all Neptune & Ouranos are 17 & 14 Earth masses respectively & Earth, our system’s largest rocky world 1 by definition - that’s a big gap in-between …)

Is this world a waterworld or a rockball? Can we actually find out somehow if it transits -or doesn’t? Another site linked to on the original “Huge News -Gliese 581c found” thread here “Okri /Systematic” notes that a lot depends on where the planet formed - if it migrated inwards it may be more a micro-Neptune; if it formed in situ where it is then it may more likely be a huge globe of rock with perhaps limited water.

Not having any 5-earth mass range planets in our solar system makes it very hard to tell what their really like - theoretical models are fascinating, their all well & good but I think it may be a case of admitting we really need more data …

You are my favorite astronomer ever.

However, from what the numbers come out as when you work out the solar constant at Gliese 581 c, it looks like this planet is hotter than Venus. I suspect the solid surface of the planet may well be a layer of high pressure ice beneath a deep atmosphere, the lower part of which may well be supercritical… light from the star would not penetrate down to the crushing depths.

The regions of the planet which experience habitable temperatures are high in the atmosphere - maybe an ecology of balloon organisms like Carl Sagan envisaged for Jupiter could exist there. If, like on Venus, the atmosphere superrotates, such organisms would be carried around the planet in a matter of days.

Meanwhile, on the outer planet, the local equivalent of climate change activists point to Gliese 581 c as an example of what happens when global warming gets out of hand…

Honest question: if the increased size is entirely a perceptual illusion, *would* the surface features be easier to spot?