Fucking Awesome wrote:
The highest-resolution radar image of Mercury’s north polar region made from the Arecibo Observatory (Harmon et al., Icarus, 211, 37-50, 2011) is shown in yellow on a mosaic of MESSENGER orbital images. Radar-bright features in the Arecibo image all collocate with areas mapped as in shadow in Mercury Dual Imaging System (MDIS) images to date, consistent with the proposal that radar-bright materials contain water ice. This image is shown in a polar stereographic projection with every 5° of latitude and 30° of longitude indicated and with 0° longitude at the bottom. On Mercury, 5° of latitude is approximately 213 km.
In short...
There likely is water ice, or material containing water ice, on Mercury's north pole.
Do I need to write anything else?
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Would someone mind awfully explaining how the goddamn this is possible? I am confounded.
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Chimaera wrote:Would someone mind awfully explaining how the goddamn this is possible? I am confounded.
Basically: the Arecibo Observatory detected highly radar reflective material on Mercury's north pole (yes, a radiotelescope on Earth can make radar photographs of Mercury ; Science is that awesome). It is theorized that this reflective material might be water ice.
A while later, MESSENGER maps Mercury's north pole. Shadowed areas on its maps line up perfectly with locations of the radar bright material.
Everywhere else something liket that happened, the material turned out to be water ice.
JULY 20TH 1969 - The day the entire world was looking up
It suddenly struck me that that tiny pea, pretty and blue, was the Earth. I put up my thumb and shut one eye, and my thumb blotted out the planet Earth. I didn't feel like a giant. I felt very, very small. - NEIL ARMSTRONG, MISSION COMMANDER, APOLLO 11
Signature dedicated to the greatest achievement of mankind.
MILDLY DERANGED PHYSICIST does not mind BREAKING the SOUND BARRIER, because it is INSURED. - Simon_Jester considering the problems of hypersonic flight for Team L.A.M.E.
Awesome. That's about all I have to say right now.
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It doesn't really surprise me at all. Water is an extremely common compound, after all, and in the bottoms of craters near the poles, it gets down near -200 C. Since Mercury has such a tiny axial tilt, a polar crater would be in constant shade, and there's no atmosphere on the planet to for heat conduction or convection. It's radiation or nothing.
Terralthra wrote:It doesn't really surprise me at all. Water is an extremely common compound, after all, and in the bottoms of craters near the poles, it gets down near -200 C. Since Mercury has such a tiny axial tilt, a polar crater would be in constant shade, and there's no atmosphere on the planet to for heat conduction or convection. It's radiation or nothing.
I'm going to totally talk out of my ass here, so don't quote me on this...
The thing is that while Mercury is partially tide locked to the Sun, it has no moon to really stabilize its rotation. So the fact that we can still find water ice in a crater at the poles would tend to suggest that its axis has nevertheless been stable since at least roughly the formation date of the crater, give or take a few million years...
I'd say it's an interesting data for astrophysicists working on exo-planets.
I'm not so sure that its axis should be particularly unstable. The instability of axial tilt is related to mostly irregular gravitational perturbations caused when mass shifts around a planet significantly or by near passes with other bodies. Earth's orbital radius is nearly 3 times Mercury's, and gravity follows the inverse-square law, so that means the gravitational force on Mercury is 9 times the force on Earth. This means any perturbation significant enough to destabilize Mercury's axial tilt would have to be correspondingly nine times as strong as a perturbation on Earth's axial tilt, given the stronger gravitational force.
To summarize, I would expect that the lack of a moon wouldn't be a problem for the stability of Mercery's axial tilt, because it has a big fucking star right there to stabilize it instead. That Mercury has a 3:2 rotation:revolution synchronization shows the domination Sol has over Mercury's movement and orientation.
Stofsk wrote:Well yeah, but that one is so obvious I don't know how anyone who wasn't pedantic would include that.
you don't argue with Simon_Jester much, do you?
Fuck though, ice on mercury.
@Terraltha - wouldn't you be getting some heat convection through the ground? I mean the rest of the planet is pretty toasty, so I'd assume that heat spreads out a bit.
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madd0ct0r wrote:@Terraltha - wouldn't you be getting some heat convection through the ground? I mean the rest of the planet is pretty toasty, so I'd assume that heat spreads out a bit.
I assume you mean conduction. Convection only occurs within fluids. And yes, some, but it's rock, mostly basaltic, from what we know about it. Rock isn't known for having high thermal conductivity. In fact, rock and rock-like materials like brick and concrete are useful because compared to many materials of similar tensile and shear strength, they're good insulators.
Well, there could some form of ice in the lower atmosphere of various gas giants, but I doubt it'd be water, and certainly not in the same form that can be found naturally on earth.
Concerning the stable axis of Mercury, I recognize that it shouldn't be unstable in the first place. But at least here we have further proof of this stability, and maybe somehow that can be useful to some astrophysicist somewhere in his quest for exoplanets and a better understanding of the universe.
It's impressive news. I just imagine all the comets it took over billions of years, hitting all over the place on Mercury, just to drop some water ice in shadowed places at the poles.
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madd0ct0r wrote:@Terraltha - wouldn't you be getting some heat convection through the ground? I mean the rest of the planet is pretty toasty, so I'd assume that heat spreads out a bit.
I assume you mean conduction. Convection only occurs within fluids. And yes, some, but it's rock, mostly basaltic, from what we know about it. Rock isn't known for having high thermal conductivity. In fact, rock and rock-like materials like brick and concrete are useful because compared to many materials of similar tensile and shear strength, they're good insulators.
facepalm - yes i meant conduction.
and while rock isn't the best of conductors, we're talking about a million year equilibrium here. There's got to be some heat moving from the hot places to the cold ones.
"Aid, trade, green technology and peace." - Hans Rosling.
"Welcome to SDN, where we can't see the forest because walking into trees repeatedly feels good, bro." - Mr Coffee
Not really. Without the atmosphere the average temperature on Earth would be around -40°C. Being a third of the distance from the sun, Mercury receives 9 times more power per square meter, but at the same time it's far less than 9 times smaller than Earth, so it receives less total energy from the sun. The day-side of Mercury only gets as hot as it does because tidal lock keeps the same area facing the sun for so long.
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I'm pretty sure that insolation and radiation would balance at the same point for any size of planet- the surface area that's getting struck by sunlight increases with the surface area, and so does the total energy being absorbed per second... but the surface to radiate light away increases at the same rate.
Wow, Ice on Mercury. Now that's insane. According to some reading I did, the temperature of that crater is like 102K. And based off it's reflectivity they are claiming that it is most likely Ice, but not ruling out the possiblity of something else.
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