Ocean Planets on the Brink of Detection 159
ZonkerWilliam writes "It seems, at least theoretically, that there may be 'ocean planets' out there in the galaxy. If there are, we are closer than ever to detecting them. The formation of such planets is fairly likely, reports the PhysOrg article, despite the lack of an obvious example in our own solar system. We may have a former ocean planetoid in the neighborhood, orbiting the planet Jupiter: the moon Europa. These water worlds are the result of system formation castoffs, gas giant wannabes that never grew large enough. If any of these intriguing object exist nearby, the recently launched CoRoT satellite will be the device we use to see it. The article explains some of the science behind 'ocean worlds', as well as the new technology we'll use to find them."
Re:One example (Score:3, Informative)
The Earth is a very large lump of iron and rock with just enough water for a few puddles to thinly cover 2/3 of its surface. The article is talking about whole planets composed almost entirely of water. Think of a bunch of melted comets that got smooshed together.
Re:No ocean planets in our own solar system... (Score:2, Informative)
Re:No ocean planets in our own solar system... (Score:0, Informative)
The earth doesn't qualify as an ocean planet because it is composed of only 1 part water which covers 3/4 of the earths surface and we do not have an average of 100 km depth the Mariana Trench is only 10.91100 kilometers deep which is believed to be the deepest point in all the Oceans on Earth.
Re:One example (Score:3, Informative)
Earth is called a "water world" because it has a hydrosphere, though. The presence of water on a planet is by no means unique (Europa, Mars, most of the asteroids in our solar system), but the presence of water in abundance in the star's green zone hasn't been seen anywhere else. Earth is the only planet in the solar system where the *surface* temperature and pressure is in the appropriate range to find a lot of liquid water.
There's a difference between a "water" world and an "ocean" world, though. A "water" world has a hydrosphere. An "ocean" world has no surface other than the hydrosphere. Europa doesn't even count, but if it were warmer it would be an "ocean" world.
Time to get my geek on. (Score:5, Informative)
Acceleration due to gravity is calculated as follows:
a = G * (m / r^2)
Since we're looking for the Sun's mass, we solve this equation for m.
m = (a * r^2) / G
The first thing we need to figure out is the value of a, or how fast things accelerate toward the sun. The earth is 1.5e11 meters from the sun, and travels in a (roughly) circular orbit once every 365.25 days (or 3.16e7 seconds). If you calculate the circumferance of the earth's orbit given the radius, you get 9.42e11 meters. The earth is moving at roughly 2.98e4 meters per second.
The next step is to figure out how far the earth falls toward the sun every second. We can do this (again, roughly) without using calculus. Let's say that, for one second, the earth continues to travel in a straight line instead of a circle. If you subtract the earth's real orbital radius from this hypothetical one, you end up with the number of meters that earth falls every second, or a. Note that this isn't an exact calculation -- I would need to use calculus to do that -- but it's still "close enough". I'm an engineer, not a scientist, so be happy I used 3.14 for pi, as opposed to "about 3."
The earth's new distance from the sun, if it travelled at a tangent for sone second, would be calculated using the Pythagorean Theorum, as follows:
d = sqrt(1.5e11 ^ 2 + 2.98e4 ^ 2) = sqrt(2.25e22 + 8.88e8) = 150000000000.00296
Subtracting the original distance from the sun, the earth has fallen about 2.96 millimeters in one second, which means that the earth is accelerating toward the sun at
m = 0.00592 * 1.5e11^2 / G
According to Google calculator:
((0.00592 (m / (s^2))) * (1.5e11^2) (m^2)) / gravitational constant = 1.9961037 × 10e30 kilograms
Now, looking up the mass of the sun:
mass of the sun = 1.98892 × 10e30 kilograms
Voila, I've just calculated the mass of the sun with less than 1% error, and I didn't even need to remember any calculus.
Re:The Good News... (Score:4, Informative)
The projected maximum rise in sea level due to total melting of glaciers is around 80m. [usgs.gov] The average elevation of exposed land is about 2870m, [ilstu.edu] which is about 35 times as high. Melting everything won't inundate the globe, but it will require relocation from low-lying areas.
Re:The Good News... (Score:2, Informative)
NASA Simulator for a water world (Score:4, Informative)
It is a very general GCM so included in the download are paleo-earth configurations. You can run a simulation of the earth from 750 million years ago [columbia.edu] when it was mostly covered in water (but also very cold) to see one possible scenario. As mentioned above, you can add CO2 and turn up or down the sun or any other GHG to see other scenarios.
Disclaimer: I'm the project developer.
Re:No ocean planets in our own solar system... (Score:4, Informative)
So why no magnetic field? No convection. Why no convection? Two possibilities. 1) The lack of tidal stresses from a comparatively large moon permitted its mantle to largely solidify already, as happened on Mars. 2) On the other hand, the LACK of tectonics may have deprived the core of a way to vent excess heat. Convection happens on Earth because the top of the mantle is cooler than the bottom, and the top is cooler BECAUSE it can let off heat through tectonics. It's a self perpetuating process. With Venus, the lack of tectonics deprived the mantle of any heat release sources other than volcanism. This would permit the Venusian mantle to get much hotter than the mantle on our own planet. The increased heat without outlet would lead to a mantle far more uniform in temperature...and a mantle that is uniformly hot will have no convection.
So it becomes a self-perpetuating cycle. Something fractured the early crust of our planet, permitting subduction. Subduction and tectonics in general introduced temperature irregularities into our mantle, which kicked off convection. Convection then drove tectonic activities by itself.
A protoplanet under bombardment would have a fairly consistent mantle temperature once bombardment began to ease. Energy imparted from impacts would spread throughout the body, and cooling would occur uniformly at the outer edges of the planet where the molten material came into contact with space. The planet would then begin cooling from the outside in, resulting in a relatively uniform crust. Again, you merely need to look at all of the other terrestrial bodies in our own solar system to confirm the model.
It appears that something "else" is required to kickstart plate tectonics. The only really major thing we can identify, that fits the models, is our moon. The giant impactor which blasted lunar material away from the Earth disrupted the mantles temperature and blasted away a signifigant portion of the lighter material which should have formed our crust. The glancing blow which the models suggest would have been required for the Giant Impactor theory would have also left the side of the planet opposite the impact relatively unscathed (aside from the many millenia of debris impacts which certainly followed). As an added bonus, the newly formed moon around the planet, comparatively large and in a tight orbit, would have induced tidal forces which helped (and still help today) to keep the mantle moving.
No impact = No giant moon, no disruption of the even cooling of the surface, no disruption of the mantle, no convection, and no tectonics. Geologically, the Earth would be Venus, only covered in 1-2 kilometers of water and with a more temperate atmospheric blanket (it would probably be a far colder planet than it is today). Aside from a volcanic island or two, the planet would be a big orbiting ball of water.
Re:Nothing like Water World, here's why: (Score:4, Informative)
No, he's referring to the Tolman-Oppenheimer-Volkoff limit - a neutron star above 3 solar masses will collapse to a black hole (or possibly a quark star), similar to Chandrasekhar's limit (about 1.44 solar masses) for forming a white dwarf. (Although because large stars blow off matter as they go through the changes, the starting mass for the star has to be better than about 8 solar masses.)
A proton couldn't become a black hole, its Schwarzschild radius is far less than a Planck length. It's generally considered that the smallest mass that can become a black hole (radius equal to the Planck length) is about 21.77 micrograms, called the Planck mass.
Re:On these planets (Score:1, Informative)
http://www.thespacereview.com/article/106/2 [thespacereview.com] - Details of Quayle's involvment with NASA
He understood, he just couldn't explain it.