Recently Discovered Exoplanet Evidently Has Rains of Pebbles

By Clay Dillow Posted 10.01.2009 at 4:00 pm 10 Comments

It's Getting Hot in Here The rocky composition and high surface temperatures on COROT-7b cause rocks to vaporize, only to condense in "rock clouds" at high altitude and rain back down as pebbles. ESO/L

Humans tend to imagine things we don't fully understand in our own image: for instance, we anthropomorphize God, most sci-fi movie aliens are some variation of a biped with two eyes, a nose and a mouth, and every planet Captain Kirk visits has an atmosphere just ripe for human respiration. But science tells us things are rarely so neat and tidy out in the great unknown, and just to prove how weird things can be out there, scientists at Washington University St. Louis ran a model of the atmosphere of COROT-7b -- an exoplanet discovered last year by the COROT space telescope -- and found that the atmosphere contains the ingredients for rocks. That's right: when it rains, it rains pebbles.

There are a lot of planets outside of our solar system, and astronomers have located about 400 of them in the past two decades orbiting stars in other parts of the galaxy. Many are gaseous giants like Jupiter, others icy like our solar system's outermost planets (or in Pluto's case, former planet). COROT-7b is a rocky mass like Earth, though twice its size. By gathering data from both COROT-7b and nearby COROT-7c, researchers determined that the planet is almost certainly made up of silicate rocks like the ones in Earth's crust. However, due to its proximity to its star (just 1.6 million miles, or 23 times closer than we are to our sun), it's likely not hospitable to life, at least not to any kind we are familiar with.

That close proximity to its star keeps it gravitationally locked in place just as the moon is to the Earth, meaning the same side of COROT-7b always faces the star. As such, it stays very, very hot there (about 4,220 degrees Fahrenheit). That kind of heat vaporizes rocks, and that's exactly what happens on COROT-7b. Using computer modeling, the team at Washington ran through four different scenarios with four different starting compositions (since the exact makeup of the planet is unknown) with the same result each time.

Just as water vaporizes in our atmosphere only to condense at higher, cooler altitudes and fall back to the Earth as rain, so do the sodium, potassium, silicon monoxide, magnesium, aluminum, calcium and iron of COROT-7b. When they condense, however, they condense into rock clouds that rain little pebbles of different types of rocks. What's more, the type of rock is dependent on altitude. The atmosphere gets colder the higher up the rock vapor goes. Since each rock or mineral has a different boiling point, the materials with the highest boiling points will condense out at lower altitudes, while the ones with lower boiling points can rise higher as vapor before condensing back into rocks.

Something tells us that if the lack of oxygen and the molten surface of COROT-7b didn't put off Captain Kirk and company, constant showers of silicate rocks might.

[Washington University St. Louis]

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10 Comments

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skillet

10/01/09 at 6:19 pm

If there is alien life I hope they have car insurance.

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quasi44

10/01/09 at 6:24 pm

Normally I refrain from the 'story bashing' I see here, but I would like to inject a note of caution here, as we have never Been to a place where we are looking at to be sure our composite imaging is actually correct. I understand that space distances allow for interference from many possible sources that could easily change our view, even with the best efforts of the operators, and those interpreting received data, and the many images from the various platforms tied to the composite. Before we go building a craft for a set of requirements that may or may not be sufficient in reality. Impressed as I have been with this set of discoveries, and the cooperation of the various entities, I believe this technique is still in its early days, and we should not rush to accept what may be skewed. That said, as always, I wait to see what is new and what is possible, so please don't think I am necessarily dismissing the work I've seen so far.

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NOM

10/01/09 at 6:43 pm

If this planet is tidally locked and the minerals condense at different levels in the atmosphere, the cold side of the planet may have bands of nearly pure minerals where the winds (which I bet are pretty strong) have carried them.

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deegeezee

10/01/09 at 7:19 pm

wouldn't the pebbles be *snow*, and rain lava?

i love analogies.

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Hurtzmyhead

10/01/09 at 10:37 pm

I find the "anthropomorphize God" comment particularly insulting... There are plenty of perfectly rational people that believe in God.

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deegeezee

10/02/09 at 3:36 am

Hurtzmyhead: yes, of course. but i think that comment just meant that some people envision God as big, old man complete with white beard. i.e. human form = anthropomorphized, which tends to show a limited imagination. rational believers probably don't believe in a giant, divine pinky toe, for example.

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jane doe

10/05/09 at 12:40 pm

Hurtzmyhead: Qualities of the Judeo-Christian god are very human for a non-human god - our imagination is quite limited.

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QIII

10/08/09 at 1:08 am

Creating gods is a difficult matter. Sometimes it takes whole cultures millenia to get something they can generally agree on, if ever at all. Often the task is so difficult that they eventually come up with a whole menagerie of gods -- and then bicker among themselves about which is the more powerful.

I want a personal god. But I've created mine and started over a number of times. I just can't seem to get all the features I want without the drawbacks I don't want.

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Dyplorus

10/11/09 at 10:42 pm

Umm...all of you who said that "we" (probably meaning everyone)think of two eyes nos------nope not everyone...my imagination was "out-of-the-box" enough to realize that looooonnngg ago (but no more than a year)

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Dyplorus

10/11/09 at 10:45 pm

and in fact, i've created a few alien races myself without anything that humans or sci-fi will usually recognize, it only requires a little treeeness, and thinking it through, and being open-minded, in fact a lot of people should be able to do that.