[Sharkfinn]

http://www.nature.com/news/kepler-spies-water-worlds-1.12825

Probably ocean planets from this article, without a mass it's uncertain, but still a big discovery, these are the most Earth-like exoplanets discovered.

[BloodEagle]

Mermaids? 

[General Battuta]

Varys is a merman

[Wobble73]

This thread is becoming very fishy 

[Nuke]

at last we have discovered the dolphin homeworld.

[Ghostavo]

I like how there's all this speculation about there being water on the planet, the composition, etc. when the article has the following line.

Jonathan Lunine, a planetary scientist at Cornell University in Ithaca, New York, says that it is impossible to know the composition of the two exoplanets because scientists have not been able to calculate their masses.

[watsisname]

What an awesome system this is.   Five detected planets, four of which are super-Earths and the other is about the size of Mars, and the outer-most two are in the habitable zone, receiving ~1.2 ± 0.2 and 0.41 ± 0.05 times the solar flux that the Earth does.  Kepler-62e is probably the most Earth-like planet we have yet discovered.

I'm curious to know what Sasselov's reasoning is that leads him to think these are probably water worlds -- without knowing their masses we don't know the density and thus bulk composition.  Sasselov is a professor of astronomy and research astrophysicist with a great deal of papers involving astrobiology and exoplanets, but the one that is being referenced here has not been published.

[Hobbie]

Here's hoping the atmosphere isn't pure helium or something.

[watsisname]

I don't know of any way for any planet to end up with a pure helium atmosphere, though that would be a neat thing to find.   Atmospheres dominated by hydrogen are more plausible for super-earths, but they'd have to be larger than these ones.

Also, this system is about 7 billion years old so these planets would have had plenty of time to build secondary atmospheres from outgassing.  So their atmospheres are probably mostly made of some combination of water and carbon.

[Hobbie]

Well, we do need a specific nitrogen-oxygen mix to breathe. 78% nitrogen, 20% oxygen, 2% other stuff like argon and CO2. The chances of us finding breathable air on one of these planets is rather slim. We also gotta worry about air pressure and gravitational effects as well.

Still, it'd be awesome if everything lined up, and seeing as they're mostly in the habitable belt, that gives us hope!

[General Battuta]

Well, we do need a specific nitrogen-oxygen mix to breathe. 78% nitrogen, 20% oxygen, 2% other stuff like argon and CO2. The chances of us finding breathable air on one of these planets is rather slim. We also gotta worry about air pressure and gravitational effects as well.

Still, it'd be awesome if everything lined up, and seeing as they're mostly in the habitable belt, that gives us hope!

We don't need a mix anywhere near that specific - various nitrox mixes are perfectly breathable, as well as pure oxygen.

e: though not all of these are super great long term

[watsisname]

Well, we do need a specific nitrogen-oxygen mix to breathe. 78% nitrogen, 20% oxygen, 2% other stuff like argon and CO2. The chances of us finding breathable air on one of these planets is rather slim. We also gotta worry about air pressure and gravitational effects as well.

Still, it'd be awesome if everything lined up, and seeing as they're mostly in the habitable belt, that gives us hope!

A planet's atmosphere cannot have appreciable oxygen unless it is being actively produced by something.  I'd say let's worry about detecting oxygen in an exoplanet's atmosphere (which is all but certain proof of the presence of photosynthetic life!) before we worry about whether the exact conditions are conducive to humans living there.

[Nuke]

i often wonder if dinosaurs would be able to survive in our atmosphere, apparently atmospheric conditions back then were different enough to be relevant.

[BritishShivans]

They can't, there's not enough oxygen nowadays compared to back then for them to survive.

[Herra Tohtori]

They can't, there's not enough oxygen nowadays compared to back then for them to survive.

Oxygen levels during Triassic, Jurassic and Cretaceous periods were lower than modern atmospheric level.

You might be thinking about the Carboniferous period, when oxygen levels peaked at 35% or so. This was actually the time of biggest insects. However, during the Permian mass extinction event, the oxygen levels dropped significantly and during Triassic period dropped even lower. In fact, the lowest oxygen levels in the last 500 million years (which is about the time frame of complex life on Earth) occurred during late Triassic and early Jurassic, at about 12%.

In fact, it's highly likely that the oxygen levels were partially responsible for the evolution of avian respiratory system in theropod dinosaurs.

Dinosaurs would have no problems breathing the current atmosphere, although the herbivores might (or might not) have trouble finding suitable vegetation for consumption. Depending on the species, they may also be sensitive to seasonal temperature variations, and may be vulnerable to new micro-organisms. But in general - dinosaurs would probably manage perfectly well in modern world environment-wise.

[BritishShivans]

They can't, there's not enough oxygen nowadays compared to back then for them to survive.

Oxygen levels during Triassic, Jurassic and Cretaceous periods were lower than modern atmospheric level.

You might be thinking about the Carboniferous period, when oxygen levels peaked at 35% or so. This was actually the time of biggest insects. However, during the Permian mass extinction event, the oxygen levels dropped significantly and during Triassic period dropped even lower. In fact, the lowest oxygen levels in the last 500 million years (which is about the time frame of complex life on Earth) occurred during late Triassic and early Jurassic, at about 12%.

In fact, it's highly likely that the oxygen levels were partially responsible for the evolution of avian respiratory system in theropod dinosaurs.

Dinosaurs would have no problems breathing the current atmosphere, although the herbivores might (or might not) have trouble finding suitable vegetation for consumption. Depending on the species, they may also be sensitive to seasonal temperature variations, and may be vulnerable to new micro-organisms. But in general - dinosaurs would probably manage perfectly well in modern world environment-wise.

Thanks for that Herra! I forgot and got my periods muddled. I'm actually not that sure about what I was trying to say here, now that I think about it. I should read up on things again.

[SypheDMar]

If Herra is  right (which I suspect he is) then oxygen levels being higher during the Triassic to Cretaceous period is something that is popular misconceived because I've heard that as well.

[watsisname]

Herra is right.

The Rise of Oxygen over the Past 205 Million Years and the Evolution of Large Placental Mammals
Implications Of The Late Paleozoic Oxygen Pulse For Physiology And Evolution

[Herra Tohtori]

The mental image people have of the environment in Dinosaur Time is that it was lush, tropical, and paradise-like. Often a mistaken imagery of giant insects like dragonflies and such is also included; to be fair there were some large insects during Dinosaur Time, but nothing like in earlier Permian era (apparently, dinosaurs were plagued by giant fly-like insects that either fed on them or laid their eggs on them as parasites).

For some reason people tend to associate this with oxygen levels (because oxygen = life, and lots of life = lots of oxygen), when in fact the Triassic period was rather arid and desolate with relatively small amounts of vegetation, and the rush of plant-life in Jurassic and Cretaceous was caused by high carbon dioxide levels (which caused excellent conditions for photosynthesis), not oxygen levels.

Rather predictably, this has often been used as a (false) evidence on why we shouldn't be worried about the rising carbon dioxide levels on current atmosphere, and that since the climate was such a lush paradise during Dinosaur Time, surely equal amount of carbon dioxide would simply restore those conditions on Earth.

Of course this doesn't take into account that we're basically burning through copious amounts of carbon that was separated from the carbon cycle by being buried underground, mostly during the (aptly named) Carboniferous era. So first of all there is a chance that we could end up with more CO₂ in the atmosphere than ever since the hellhole days of Earth's early composition, and secondly since the Sun's radiation output is constantly growing, Earth is receiving more radiation now than it did during the Carboniferous peak. So it is theoretically possible to end up with a man-made runaway greenhouse effect a lá Venus.

And even if that doesn't happen, causing rapid changes in the environment will cause massive humanitarian crisis, no matter what the end state will be. So yeah, just had to say that since it was somewhat related.

Carry on.

[Sharkfinn]

Going back to the planets, here's a preprint for a paper on water-world potential (http://arxiv.org/abs/1304.5058), to be published in APJ.