Lunar Temperature - Revision history

Farred: restoring version by Apsmith

2011-11-10T19:00:45Z

restoring version by Apsmith

207.216.61.178 at 04:14, 9 November 2011

2011-11-09T04:14:47Z

106.187.35.208: zehEHpwKrMsEd

2011-10-30T04:02:26Z

zehEHpwKrMsEd

Apsmith: clarification on emissivity and reflectance/albedo

2007-06-14T16:33:07Z

clarification on emissivity and reflectance/albedo

Apsmith: fixed up some math

2007-06-13T03:53:48Z

fixed up some math

Apsmith: categorizing

2007-06-13T03:51:33Z

categorizing

Cfrjlr: Category:Selenology

2007-06-10T16:41:03Z

Category:Selenology

Cfrjlr: typo

2007-06-10T16:39:05Z

typo

Strangelv: made not linkless; added stub tag (still needs sorting)

2007-06-10T14:47:28Z

made not linkless; added stub tag (still needs sorting)

Cfrjlr: info

2007-06-09T13:06:06Z

info

New page

The temperature of the Moon varies greatly due to a number of factors.

The Moon is heated entirely by the Sun. Unlike geologically active bodies, the Moon is not know to have any internal heat source, and its surface is heated entirely by the Sun.

During the lunar day the temperature is very high. At night the temperature also drops to become very cold.

The temperature also varies according to the latitude, at higher latitudes the sunlight intensity is lower due to the angle presented by the lunar surface to the solar line of sight.

Temperature also varies according to shadow, area in permanent shadow (e.g. craters at the pole) are thought to be permanently cold, and possibly cold traps holding volatile materials.

There is also some question as to whether the intensity of the Sun itself is varying, and whether that can be monitored by measuring the surface temperature of the Moon.

@@ Line 1: / Line 1: @@
+The surface temperature of the [[Luna|Moon]] varies considerably with location and the relative position of the Sun. Unlike geologically active bodies, the Moon no longer has an internal heat source, so heating comes almost entirely from the Sun (at night the lunar surface is warmed slightly by Earth).
 With no atmosphere and a surface made up almost entirely of rocky materials with low thermal conductivity and relatively low heat capacity, during the [[Lunar Day|lunar day]] the surface temperature quickly reaches equilibrium with incoming solar radiation. The [http://en.wikipedia.org/wiki/Stefan-Boltzmann_law Stefan-Boltzmann equation] sets the numbers:
 <div style="text-align: center;">
 <math> I = \epsilon\sigma T^{4}</math>
 </div>
 where ''I'' represents absorbed solar energy per unit area, ''T''  is the absolute surface temperature (kelvins), ''<math>\epsilon</math>'' is the [[Lunar Emissivity|emissivity]], and ''<math>\sigma</math>'' is Stefan's constant, 5.67x10^-8 in metric units.
 For a surface with the sun directly overhead, for example a horizontal region near the equator at lunar noon, ''I'' is the solar constant in Earth's neighborhood, about 1366 W/m^2, minus the portion [[Lunar Albedo|reflected]].  Since the emissivity is close to 1 minus the reflectance, those two terms cancel out, and inverting the equation gives the maximum day-time high on the Moon: 394 K or about 120 degrees C.
 When the sun's not directly overhead whether you are at the equator during lunar morning or evening, near the poles, or looking at a rock face sharply angled to the horizontal, the surface temperature will be lowered because the same solar energy is spread over a larger area.
 <div style="text-align: center;">
 <math>I = 1366 \cos(\theta) W/m^2</math>
 </div>
 where ''<math>\theta</math>'' is the angle of the Sun's position relative to a line perpendicular to the surface. Because the lunar rotational axis is tilted only 1.5 degrees from the ecliptic, solar angles at noon are always within 1.5 degrees of the lunar latitude value.
 For an angle of 30 degrees, (maximum temperature for a horizontal surface at latitude 30 degrees N or S, or equatorial temperature at roughly plus or minus two Earth days from lunar "noon"), ''T'' is then 380 K, or 107 degrees C. At 60 degrees, the temperature is still 331 K or 58 degrees C. At 75 degrees we reach about 281 K or 8 degrees C. At 85 degrees the equilibrated temperature drops to 214 K or -59 degrees C. At the lunar poles there are believed to be regions which never receive direct sunlight. If they don't receive significant warming from higher elevation surfaces that are in direct sunlight, they would be equilibrated only with the thermal background radiation of deep space at 2-3 K (-270 degrees C), and would likely form cold traps holding volatile materials.
 During the [[Lunar Night|night]] the surface temperature drops further as the rocks radiate away the energy they've absorbed during the day time, with regions near the lunar equator dropping to about 120 K or -150 degrees C by the end of the night.
 The temperature drop is limited by conduction of heat from layers several meters below the surface, which maintain a roughly steady average temperature that can also be determined from the Stefan-Boltzmann law. In this case 'I' represents the incoming solar energy averaged over a full day-night cycle
 <div style="text-align: center;">
 <math>I_{ave} = 1366 \cos(\theta)/\pi W/m^2 </math>
 </div>
 so at the equator ''T'' is about 296 K, or a comfortable 23 degrees C if you bury yourself sufficiently. At 60 degrees that drops to 249 K or -24 degrees C. The average subsurface temperature near the poles (85 degrees and higher) would be below 160 K or -110 degrees C.
 [[Category:Selenology]]
 {{Physics Stub}}

← Older revision		Revision as of 04:14, 9 November 2011
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−	~~Tip top stuff~~. I'~~ll ecpxet more now~~.	+	-
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		+
		+
		+	+
		+	-
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		+	With no atmosphere and a surface made up almost entirely of rocky materials with low thermal conductivity and relatively low heat capacity, during the [[Lunar Day\|lunar day]] the surface temperature quickly reaches equilibrium with incoming solar radiation. The [http://en.wikipedia.org/wiki/Stefan-Boltzmann_law Stefan-Boltzmann equation] sets the numbers:
		+
		+	+
		+	-
		+
		+
		+
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		+	-
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		+	<div style="text-align: center;">
		+
		+	+
		+	-
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		+	<math> I = \epsilon\sigma T^{4}</math>
		+
		+	+
		+	-
		+
		+	</div>
		+
		+	+
		+	-
		+
		+
		+
		+	+
		+	-
		+
		+	where ''I'' represents absorbed solar energy per unit area, ''T'' is the absolute surface temperature (kelvins), ''<math>\epsilon</math>'' is the [[Lunar Emissivity\|emissivity]], and ''<math>\sigma</math>'' is Stefan's constant, 5.67x10^-8 in metric units.
		+
		+	+
		+	-
		+
		+
		+
		+	+
		+	-
		+
		+	For a surface with the sun directly overhead, for example a horizontal region near the equator at lunar noon, ''I'' is the solar constant in Earth's neighborhood, about 1366 W/m^2, minus the portion [[Lunar Albedo\|reflected]]. Since the emissivity is close to 1 minus the reflectance, those two terms cancel out, and inverting the equation gives the maximum day-time high on the Moon: 394 K or about 120 degrees C.
		+
		+	+
		+	-
		+
		+
		+
		+	+
		+	-
		+
		+	When the sun's not directly overhead whether you are at the equator during lunar morning or evening, near the poles, or looking at a rock face sharply angled to the horizontal, the surface temperature will be lowered because the same solar energy is spread over a larger area.
		+
		+	+
		+	-
		+
		+
		+
		+	+
		+	-
		+
		+	<div style="text-align: center;">
		+
		+	+
		+	-
		+
		+	<math>I = 1366 \cos(\theta) W/m^2</math>
		+
		+	+
		+	-
		+
		+	</div>
		+
		+	+
		+	-
		+
		+
		+
		+	+
		+	-
		+
		+	where ''<math>\theta</math>'' is the angle of the Sun's position relative to a line perpendicular to the surface. Because the lunar rotational axis is tilted only 1.5 degrees from the ecliptic, solar angles at noon are always within 1.5 degrees of the lunar latitude value.
		+
		+	+
		+	-
		+
		+
		+
		+	+
		+	-
		+
		+	For an angle of 30 degrees, (maximum temperature for a horizontal surface at latitude 30 degrees N or S, or equatorial temperature at roughly plus or minus two Earth days from lunar "noon"), ''T'' is then 380 K, or 107 degrees C. At 60 degrees, the temperature is still 331 K or 58 degrees C. At 75 degrees we reach about 281 K or 8 degrees C. At 85 degrees the equilibrated temperature drops to 214 K or -59 degrees C. At the lunar poles there are believed to be regions which never receive direct sunlight. If they don't receive significant warming from higher elevation surfaces that are in direct sunlight, they would be equilibrated only with the thermal background radiation of deep space at 2-3 K (-270 degrees C), and would likely form cold traps holding volatile materials.
		+
		+	+
		+	-
		+
		+
		+
		+	+
		+	-
		+
		+	During the [[Lunar Night\|night]] the surface temperature drops further as the rocks radiate away the energy they've absorbed during the day time, with regions near the lunar equator dropping to about 120 K or -150 degrees C by the end of the night.
		+
		+	+
		+	-
		+
		+
		+
		+	+
		+	-
		+
		+	The temperature drop is limited by conduction of heat from layers several meters below the surface, which maintain a roughly steady average temperature that can also be determined from the Stefan-Boltzmann law. In this case 'I' represents the incoming solar energy averaged over a full day-night cycle
		+
		+	+
		+	-
		+
		+
		+
		+	+
		+	-
		+
		+	<div style="text-align: center;">
		+
		+	+
		+	-
		+
		+	<math>I_{ave} = 1366 \cos(\theta)/\pi W/m^2 </math>
		+
		+	+
		+	-
		+
		+	</div>
		+
		+	+
		+	-
		+
		+
		+
		+	+
		+	-
		+
		+	so at the equator ''T'' is about 296 K, or a comfortable 23 degrees C if you bury yourself sufficiently. At 60 degrees that drops to 249 K or -24 degrees C. The average subsurface temperature near the poles (85 degrees and higher) would be below 160 K or -110 degrees C.
		+
		+	+
		+	-
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		+	-
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		+	[[Category:Selenology]]
		+
		+	+
		+	-
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		+	+
		+	-
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		+	{{Physics Stub}}

← Older revision		Revision as of 04:02, 30 October 2011
Line 1:		Line 1:
−	~~The surface temperature of the [[Luna\|Moon]] varies considerably with location and the relative position of the Sun~~. ~~Unlike geologically active bodies, the Moon no longer has an internal heat source, so heating comes almost entirely from the Sun (at night the lunar surface is warmed slightly by Earth).~~	+	Tip top stuff. I'll ecpxet more now.
−
−	With no atmosphere and a surface made up almost entirely of rocky materials with low thermal conductivity and relatively low heat capacity, during the [[Lunar Day\|lunar day]] the surface temperature quickly reaches equilibrium with incoming solar radiation. The [http://en.wikipedia.org/wiki/Stefan-Boltzmann_law Stefan-Boltzmann equation] sets the numbers:
−
−	~~<div style="text-align: center;">~~
−	~~<math> I = \epsilon\sigma T^{4}</math>~~
−	~~</div>~~
−
−	where ''I'' represents absorbed solar energy per unit area, ''T'' is the absolute surface temperature (kelvins), ''<math>\epsilon</math>'' is the [[Lunar Emissivity\|emissivity]], and ''<math>\sigma</math>'' is Stefan's constant, 5.67x10^-8 in metric units.
−
−	For a surface with the sun directly overhead, for example a horizontal region near the equator at lunar noon, ''I'' is the solar constant in Earth's neighborhood, about 1366 W/m^2, minus the portion [[Lunar Albedo\|reflected]]. Since the emissivity is close to 1 minus the reflectance, those two terms cancel out, and inverting the equation gives the maximum day-time high on the Moon: 394 K or about 120 degrees C.
−
−	When the sun's not directly overhead whether you are at the equator during lunar morning or evening, near the poles, or looking at a rock face sharply angled to the horizontal, the surface temperature will be lowered because the same solar energy is spread over a larger area.
−
−	~~<div style="text-align: center;">~~
−	~~<math>~~I ~~= 1366 \cos(\theta) W/m^2</math>~~
−	~~</div>~~
−
−	~~where~~ ''<math>\theta</math>'' is the angle of the Sun's position relative to a line perpendicular to the surface. Because the lunar rotational axis is tilted only 1.5 degrees from the ecliptic, solar angles at noon are always within 1.5 degrees of the lunar latitude value.
−
−	For an angle of 30 degrees, (maximum temperature for a horizontal surface at latitude 30 degrees N or S, or equatorial temperature at roughly plus or minus two Earth days from lunar "noon"), ''T'' is then 380 K, or 107 degrees C. At 60 degrees, the temperature is still 331 K or 58 degrees C. At 75 degrees we reach about 281 K or 8 degrees C. At 85 degrees the equilibrated temperature drops to 214 K or -59 degrees C. At the lunar poles there are believed to be regions which never receive direct sunlight. If they don't receive significant warming from higher elevation surfaces that are in direct sunlight, they would be equilibrated only with the thermal background radiation of deep space at 2-3 K (-270 degrees C), and would likely form cold traps holding volatile materials.
−
−	During the [[Lunar Night\|night]] the surface temperature drops further as the rocks radiate away the energy they've absorbed during the day time, with regions near the lunar equator dropping to about 120 K or -150 degrees C by the end of the night.
−
−	The temperature drop is limited by conduction of heat from layers several meters below the surface, which maintain a roughly steady average temperature that can also be determined from the Stefan-Boltzmann law. In this case 'I' represents the incoming solar energy averaged over a full day-night cycle
−
−	~~<div style="text-align: center;">~~
−	~~<math>I_{ave} = 1366 \cos(\theta)/\pi W/m^2 </math>~~
−	~~</div>~~
−
−	so at the equator ''T'' is about 296 K, or a comfortable 23 degrees C if you bury yourself sufficiently. At 60 degrees that drops to 249 K or -24 degrees C. The average subsurface temperature near the poles (85 degrees and higher) would be below 160 K or -110 degrees C.
−
−	~~[[Category:Selenology]]~~
−
−	~~{{Physics Stub}}~~

@@ Line 7: / Line 7: @@
 </div>
-where ''I'' represents incoming solar energy per unit area, ''T''  is the absolute surface temperature (kelvins), ''<math>\epsilon</math>'' is a ratio close to 1 for the lunar surface, and ''<math>\sigma</math>'' is Stefan's constant, 5.67x10^-8 in metric units.
+where ''I'' represents absorbed solar energy per unit area, ''T''  is the absolute surface temperature (kelvins), ''<math>\epsilon</math>'' is the [[Lunar Emissivity|emissivity]], and ''<math>\sigma</math>'' is Stefan's constant, 5.67x10^-8 in metric units.
-For a surface with the sun directly overhead, for example a horizontal region near the equator at lunar noon, ''I'' is the solar constant in Earth's neighborhood, about 1366 W/m^2. Inverting the equation gives the maximum day-time high on the Moon: 394 K or about 120 degrees C.
+For a surface with the sun directly overhead, for example a horizontal region near the equator at lunar noon, ''I'' is the solar constant in Earth's neighborhood, about 1366 W/m^2, minus the portion [[Lunar Albedo|reflected]].  Since the emissivity is close to 1 minus the reflectance, those two terms cancel out, and inverting the equation gives the maximum day-time high on the Moon: 394 K or about 120 degrees C.
 When the sun's not directly overhead whether you are at the equator during lunar morning or evening, near the poles, or looking at a rock face sharply angled to the horizontal, the surface temperature will be lowered because the same solar energy is spread over a larger area.

@@ Line 25: / Line 25: @@
 The temperature drop is limited by conduction of heat from layers several meters below the surface, which maintain a roughly steady average temperature that can also be determined from the Stefan-Boltzmann law. In this case 'I' represents the incoming solar energy averaged over a full day-night cycle
-<math>I<sub>ave</sub> = 1366 cos(\theta)/\pi W/m^2 </math>
+<div style="text-align: center;">
 so at the equator ''T'' is about 296 K, or a comfortable 23 degrees C if you bury yourself sufficiently. At 60 degrees that drops to 249 K or -24 degrees C. The average subsurface temperature near the poles (85 degrees and higher) would be below 160 K or -110 degrees C.

@@ Line 7: / Line 7: @@
 The temperature also varies according to the latitude, at higher latitudes the sunlight intensity is lower due to the angle presented by the lunar surface to the solar line of sight.
-Temperature also varies according to shadow, area in permanent shadow (e.g. craters at the pole) are thought to be permanently cold, and possibly cold traps holding volatile materials.
+Temperature also varies according to shadow, areas in permanent shadow (e.g. craters at the pole) are thought to be permanently cold, and possibly cold traps holding volatile materials.
 There is also some question as to whether the intensity of the Sun itself is varying, and whether that can be monitored by measuring the surface temperature of the Moon.
 {{stub}}

@@ Line 1: / Line 1: @@
-The temperature of the [[Luna|Moon]] varies greatly due to a number of factors.
+The surface temperature of the [[Luna|Moon]] varies greatly due to a number of factors.
-The Moon is heated entirely by the Sun. Unlike geologically active bodies, the Moon is not know to have any internal heat source, and its surface is heated entirely by the Sun.
+The Moon is heated entirely by the Sun. Unlike geologically active bodies, the Moon is not known to have any internal heat source, and its surface is heated entirely by the Sun.
 During the [[Lunar Day|lunar day]] the temperature is very high. At [[Lunar Night|night]] the temperature also drops to become very cold.