Greebo Posted February 3, 2011 Report Share Posted February 3, 2011 To dismiss the hypothesis that life is not unique, we need proof. Only then can we safely assume that life is abundant in the Universe. I think you mean "the hypothesis that life is unique" ? Quote Link to comment Share on other sites More sharing options...
Tanaka Posted February 3, 2011 Report Share Posted February 3, 2011 I think you mean "the hypothesis that life is unique" ? Yes, sorry. Quote Link to comment Share on other sites More sharing options...
DancingBear Posted February 7, 2011 Author Report Share Posted February 7, 2011 That is an interesting assertion which I trust you are able to prove with actual physics? From Wikipedia: Because of the atmosphere it is not useful and hardly possible to give an object near the surface of the Earth a speed of 11.2 km/s, as these speeds are too far in the hypersonic regime for most practical propulsion systems and would cause most objects to burn up due to atmospheric compression or be torn apart by atmospheric friction. For an actual escape orbit a spacecraft is first placed in low Earth orbit and then accelerated to the escape velocity at that altitude, which is a little less — about 10.9 km/s. The required change in speed, however, is far less because from a low Earth orbit the spacecraft already has a speed of approximately 8 km/s. The escape velocity for Mars is 5 km/s, or 5000 m/s, according to Wikipedia (hopefully no Liberals are fudging these results!). In fact, most of Mars is Basalt. Basalt melts at about 984° to 1260° and granite at about 1215° to 1260°. See the "Melting Intervals of Rocks" section of that link. The specific heat of Basalt. So the specific heat (the amount of energy required to raise the temperature of one kilogram of a substance by one degree) of Basalt is .84 kJ/kg. On discovery, the meteorite's mass was 1.93 kg, or 1930 grams. Because the melting point of Basalt is around 1000 degrees, to melt two kilograms of basalt requires 1680 kJ. The work required to reach 5 km/s from rest for a 1 kg object is 5,000,000 joules. 5000 kJ is greater than 1680 kJ. Therefore any rocks blasted from the Basalt surface of Mars would melt from the event. Furthermore, the rock would experience extreme heating from the Earth's atmosphere when it entered at the same velocity and slammed into the ground. This here says that the Martian surface has no young craters which could account for the meteorite. The only plausible alternative event that could generate the energy necessary to reach that speed (correct me if I'm wrong) is volcanic activity. In this case it would be even more likely that the rock was molten during some portion of it's journey to earth. The final two paragraphs in the article about the meteorite seem to indicate that the evidence was of the presence of water, not bacteria. I'm not sure how carbonate disks and tiny magnetite crystals react under extreme heat. Quote Link to comment Share on other sites More sharing options...
Greebo Posted February 7, 2011 Report Share Posted February 7, 2011 The escape velocity for Mars is 5 km/s, or 5000 m/s, according to Wikipedia (hopefully no Liberals are fudging these results!). In fact, most of Mars is Basalt. Basalt melts at about 984° to 1260° and granite at about 1215° to 1260°. See the "Melting Intervals of Rocks" section of that link. The specific heat of Basalt. So the specific heat (the amount of energy required to raise the temperature of one kilogram of a substance by one degree) of Basalt is .84 kJ/kg. On discovery, the meteorite's mass was 1.93 kg, or 1930 grams. Because the melting point of Basalt is around 1000 degrees, to melt two kilograms of basalt requires 1680 kJ. The work required to reach 5 km/s from rest for a 1 kg object is 5,000,000 joules. 5000 kJ is greater than 1680 kJ. True so far Therefore any rocks blasted from the Basalt surface of Mars would melt from the event. Not correct. Acceleration certainly imparts some heat - but the force that generates 5000kJ of movement energy isn't also going to create 5000kJ of heat. It takes much more movement energy to lift the space shuttle into orbit - but it doesn't melt on the way up. Why? Because the energy expended is in the form of motion - not heat. Furthermore, the rock would experience extreme heating from the Earth's atmosphere when it entered at the same velocity and slammed into the ground. Also false - iron and other solid meteors pass through the atmosphere and survive impact intact (or fragmented - not melted) quite literally all the time. Doubt it? Hose off your roof sometime - then set up a filtration system to catch smallish particles in your drainspouts, wait a few days, and hose it down again. Run a magnet over the rocks and such you capture. Those which stick to the magnet will be new meteorites. Quote Link to comment Share on other sites More sharing options...
DancingBear Posted February 7, 2011 Author Report Share Posted February 7, 2011 Not correct. Could you reply to that first quote I provided from Wikipedia in the box. It says something along the lines of "atmospheric friction would tear apart objects that reach Earth's escape velocity." I also read something about how Space Shuttles don't achieve escape velocity from the surface, they accelerate as they rise. However, a rock blasted from the surface of a planet couldn't accelerate; all of it's kinetic energy would need to be realized at once in order to reach a speed required to exit the planetary gravity. Meteorites don't go into low-Mars orbit and then accelerate into space. Quote Link to comment Share on other sites More sharing options...
Steve D'Ippolito Posted February 8, 2011 Report Share Posted February 8, 2011 Still, a large enough meteor does not melt in the time it takes to get through the earth's atmosphere and wouldn't do so if fired upward at that velocity (as you describe), either--it's simply the reverse of what normally happens. And there would be less of an effect being blasted off Mars--lower escape velocity and *much* thinner atmosphere (though it may have been thicker in the past). Quote Link to comment Share on other sites More sharing options...
Greebo Posted February 8, 2011 Report Share Posted February 8, 2011 Could you reply to that first quote I provided from Wikipedia in the box. It says something along the lines of "atmospheric friction would tear apart objects that reach Earth's escape velocity." "Torn apart" doesn't mean vaporized or melted through and through. I suggest you watch "meteorite men" if you need concrete proof that meteors can make it to the Earth's surface without being vaporized. I also read something about how Space Shuttles don't achieve escape velocity from the surface, they accelerate as they rise. However, a rock blasted from the surface of a planet couldn't accelerate; all of it's kinetic energy would need to be realized at once in order to reach a speed required to exit the planetary gravity. Meteorites don't go into low-Mars orbit and then accelerate into space. Fair point - but still - great amounts of that kinetic energy is realized as movement energy - and only some of it is converted to heat energy. Think of it like this: Put a pile of dynamite in a shallow pit and cover it with rocks. Explode the dynamite. The rocks fly. Some probably get warm - but few will be really hot - but they'll be flying. Heck - watch Mythbusters blow up a concrete truck - the dang thing's in pieces but none of the pieces are *melted* - they're ripped apart by the explosive tearing from within. Smaller scales - but the same principle applies. Quote Link to comment Share on other sites More sharing options...
Greebo Posted February 8, 2011 Report Share Posted February 8, 2011 Oh yeah - wrt the bolded part of your wiki quote... one other point. Most is not all. Quote Link to comment Share on other sites More sharing options...
ctrl y Posted April 19, 2011 Report Share Posted April 19, 2011 Wow, apparently someone on OO.net has been abducted... is a troll. ^Fixed. Quote Link to comment Share on other sites More sharing options...
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