Exoplanet Has Showers of Pebbles 341
mmmscience writes "The newly-discovered exoplanet COROT-7b has an unusual form of precipitation: rocks. Because it orbits so close to its sun, the temperature on its sun-facing side is around 4220 degrees Fahrenheit. That's hot enough for rocks to vaporize — not unlike water evaporating on Earth. And, like Earth, when the vapor cools in the upper atmosphere, it forms clouds and begins to rain. But instead of water, COROT-7b gets a shower of pebbles."
Re:Summary inaccurate (Score:5, Interesting)
True. Also, I'm wondering if "pebbles" is an appropriate description of the condensed rock or if it wouldn't be more aptly described as "sand" or even "dust". Raindrops stick together; depending on how quickly the rock condenses, it might not have time to grow very large. (Then again, it could grow like hail, if the rock was in the liquid state for any significant amount of time.)
Rock Rainbows? (Score:5, Interesting)
Given that different material will have different melting temperatures, that should lead to the different metals coalescing at different heights. At sunset, there ought to be a layering affect as the last rocks fall back to the surface, a rock rainbow in effect. Of course, it probably won't last long with the whole planet being molten.
Solid precipitation and dinnerplate planets (Score:2, Interesting)
Fallout (Score:5, Interesting)
That has happened on Earth too. We call it Fallout.
I am not kidding. A surface nuclear burst in the megaton range will vaporize millions of tons of rock and soil. This material will cool, condense, and and fall as
little pebbles or hail. In this case, it's radioactive, but otherwise the physics is the same.
Meanwhile on COROT-7b (Score:5, Interesting)
Meanwhile on COROT-7b scientists find a new planet so cold that water would actually create "oceans" on the surface , and even freeze at the poles.
They laugh at the though ever existing on that planet.
Re:Fallout (Score:5, Interesting)
To enjoy a natural one, without the radioactive waste, all you need is a volcano eruption.
Re:Solid precipitation and dinnerplate planets (Score:3, Interesting)
I would expect that the elements/molecules with higher melting points would migrate to the sunward side, while more volatile stuff would end up in the shadows. Would you have something like a "shield" of aluminum oxide guarding an ocean of iron?
Conveyor-belt planet (Score:5, Interesting)
Re:Non-migratory (Score:3, Interesting)
In this case, yes. The planet would be tidal locked, due to its proximity to the sun. Less volatile components would be the first to boil off into a gaseous state. There would be a "wind" that carries the gaseous components around to the shadowed side of the planet, where it would cool and fall. Repeat for a few million years, and you'd have a nice stratisfication based on volatililty (or lack thereof).
Re:Wow (Score:2, Interesting)
Whoosh. [wikipedia.org]
Also, 29 Aug 2007 was the date of the 2007 United States Air Force nuclear weapons incident [wikipedia.org]. Ironic?
Re:Wow (Score:5, Interesting)
The planet is tidally locked. Just stay on the dark side of the planet. The equilibrium temperature there is 59F [wustl.edu] -- not bad at all.
One thing that occurs to me is that if the mass transfer rate is as high as they're suggesting -- and I have no reason to suspect otherwise -- it seems to me that this planet would be *highly* tectonically active. Unlike rain, which just runs off, the pebbles will stick around where they fall. This means that the crust will have a lot of weight bearing down on it on the cold side, sinking into the mantle and likely leading to heavy volcanism and tectonic activity. And the erosion of the hot side should lead to an upwelling of exposed mantle material as the planet tries to relax into a sphere.
The awesome thing is, with such a reasonable temperature on the cool side, it could actually be habitable to LAWKI -- except for that likely lack of water thing, (unless there's been heavy cometary activity since the planet became tidally locked).
This planet must have an incredible range of minerals, way unlike anything on Earth -- the star basically mining the crust and even mantle on one side and depositing it after chemical vapor deposition onto the other side. If we ever go interstellar as a species, I wouldn't be surprised to see heavy mining activity on planets like that.
Re:Wow (Score:5, Interesting)
Oh, and sweet -- Some more highlights after further reading:
"Sodium, potassium, silicon monoxide and then oxygen -- either atomic or molecular oxygen -- make up most of the atmosphere." But there are also smaller amounts of the other elements found in silicate rock, such as magnesium, aluminum, calcium and iron. ... As you go higher the atmosphere gets cooler and eventually you get saturated with different types of 'rock' the way you get saturated with water in the atmosphere of Earth ... Elemental sodium and potassium, which have very low boiling points in comparison with rocks, do not rain out but would instead stay in the atmosphere, where they would form high gas clouds buffeted by the stellar wind from COROT-7.
So... the only one of those things that will be a gas at the surface on the far side is oxygen. The article says the atmosphere may not be breathable, but I have to wonder... why not?
Also, in the case what what condenses in the atmosphere is crystaline (I don't see anywhere which suggests whether they would be or not -- it all depends on how fast it cools), look at the list of the raining minerals:
enstatite, corundum, spinel, and wollastonite.
Enstatite can be a gemstone. Crystals of corundum are otherwise known as ruby and sapphire. There are many types of spinels, a number of whose crystals are considered gemstones. Etc. So *if* what condenses is crystalline, it could literally be raining gems on that planet.
Re:Let's not exaggerate (Score:3, Interesting)
From underground nuclear tests, the "melt cavity" created by vaporization of rock and the flow of liquefied rock is about 2000 cubic metres per kiloton, so the OP's estimate is about right, assuming one half of the energy is lost to the air by a surface explosion.
Re:Not unusual (Score:1, Interesting)
Hey! That's "ugly bags of mostly water" to you.
Re:Not unusual (Score:5, Interesting)
Re:Oops (Score:3, Interesting)
Yeah but how big is it? Without Atmosphere it can get very small to basically non existent.
Re:Solid precipitation and dinnerplate planets (Score:3, Interesting)
Unless the planet is very small, no matter where or how you move material around, it's going to return to a roughly spherical shape, regardless. In fact, a big part of the definition of "planet" is some mass large enough that gravity forces it into a sphere.
Now, you could imagine a planet where this front-to-back migration actually stirs the planet. That would be cool.
Re:Wow (Score:2, Interesting)
So *if* what condenses is crystalline, it could literally be raining gems on that planet.
Thanks a bunch, dude! Now that you told the effing world about it every punk in the galaxy will come flying bucket in hand. (tentacle/suction cup/etc) Why exactly do you think we stressed the "unbreathable atmosphere" etc? Thanks again, buddy.
Re:Not unusual (Score:3, Interesting)
Absolutely right. What we consider liquid and solid depends on our local environment. In the outer planets of our solar system, water is a rock. It behaves just like rocks here on Earth do: it faults tectonically, crystallizes in various forms, and differentiates into crust, mantle, and core. These bodies have "hydro-"logical cycles made up of methane, which is normally a gas for us.
It's not unusual at all for something we consider to a be a "rock" actually form the hydrological cycle for a much warmer body.