![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 |
I am doing a project in school. We have to design a planet and the planet that my partner and i designed is completly water except for a few scattered volcanoes. Would animals like penguins and walruses be able to survive on a planet like this? Please answer ASAP!!!!!
What is the role that impact cratering had in history on the formation of terrestrial planets? —The preceding unsigned comment was added by 149.169.207.32 ( talk • contribs) on 00:17, 1 September 2006.
I don't think the use of this term is appropriate. The planemo article says hardly anyone uses it, so I think it is not right here. Also, why apply the term to only two of the moons, all "rounded bodies" qualify for the term. HarryAlffa ( talk) 18:16, 1 June 2009 (UTC)
In the section on extrasolar planets, the term "fusing star" is used and linked to another article ("Solar Nucleosynthesi", I think?). The other article does not explain the term "fusing star". I recommend changing the term "fusing star" for the title of the other article. -- Eddylyons ( talk) 23:30, 14 August 2009 (UTC)
Why does the first sentence of the article regard 'inner planet' as an synonym of 'terrestrial planet'? The fact that all terrestrial planets in our solar system are inner planets (that is, planets between the sun and de asteroid belt) says nothing about the situation in other planetary systems. As a result, the current article is wrong to suggest that alle terrestrial exo-planets are inner planets too. DaMatriX ( talk) 22:49, 15 December 2009 (UTC)
-- MathFacts ( talk) 06:30, 20 December 2009 (UTC)
Under Terrestrial_worlds, I believe any required wiggle room can be changed by changing "referred to as geophysical planets" to "referred to as geophysical worlds", if need be. Though I am going to try and think about this for a day. I also did not realize the solar terrestrial planets section contained a discussion about worlds when I made my first edit. Hmm walked into a can of worms? -- Kheider ( talk) 10:01, 21 December 2009 (UTC)
I've removed the following section from the article:
It is not uncommon for natural satellites that are in hydrostatic equilibrium to be referred to as terrestrial worlds. [1] The seven moons that are occasionally referred to as terrestrial worlds are: Earth's Moon, Io, Europa, Ganymede, Callisto, Titan, and Triton. [1] Planetary scientist Alan Stern has informally suggested such bodies can be referred to as geophysical planets. [2] There are 19 known satellites that meet the geophysical requirement of a planet, though since they orbit planets they cannot be considered planets themselves. The question is should some of these objects be considered as evolved icy bodies rather than terrestrial bodies? Titan looks and behaves more like Earth than any other body in the Solar System. [3] Titan is known to have stable pools of liquid on the surface. [3]
Titan showing surface and atmospheric details Volcanos on Io constantly re-surface the satellite Europa is believed to have a subsurface ocean False color image of Ganymede A cloud over the limb of TritonIn addition, Earth's moon and Jupiter's satellites Io and Europa can also be regarded as terrestrial worlds. [1] Io and Europa have mainly rocky compositions despite forming beyond the frost line. This may be because the region of the circum-Jovian disc in which they formed was kept too warm by radiation from the proto-Jupiter to contain large quantities of icy material.
As mentioned on Kheider's talk page, this appears to be putting too much weight on an unofficial, informal forum post, and needs much more in the way of verifiable sourcing. At present, it is a case of undue weight (unless, again, more sources are provided. I'd suggest that the best course is to develop the text here, rather than in the artcile, until agreement is reached as to the best approach. -- Ckatz chat spy 10:28, 21 December 2009 (UTC)
Dr. James Schombert has also stated, (at bottom of page) "Large amounts of outgassing have drained the inner moons, Io and Europa of their icy materials making them rich in rocky materials." I agree that we need to make it clear that the concept is inherently ambiguous nor does it have an official definition. When does something go from rocky to icy? How do you define Earth-like? In the pre-voyager era, Earth-like pretty much meant non- gas giant since we knew almost nothing about the large moons of the solar system. -- Kheider ( talk) 21:12, 23 December 2009 (UTC)
Exo- water planets could result from inward planetary migration and originate as protoplanets that formed from volatile ice-rich material beyond the snow-line but that never attained masses sufficient to accrete large amounts of H/He nebular gas. Water worlds might be thought of as a bigger and hotter version of Jupiter's Galilean moons. -- Kheider ( talk) 01:56, 24 December 2009 (UTC)
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cite web}}
: External link in |author=
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help)
This article claims the moon lacks an iron core. But if I remember right... http://en.wikipedia.org/wiki/Moon#Internal_structure Yes, even elsewhere on Wikipedia it is noted to have "an iron-rich core". Which is it? Or is there some threshold for "made of iron" that the moon's "iron-rich" core not actually cross? Someone who knows more should correct it. Thanks, NickRinger ( talk) 17:25, 4 May 2011 (UTC)
According to that table, Gliese 581c is smaller than 581e. But the latter is much lighter AND closer to the star (roughly implying higher density), so shouldn't 581e be the smaller one of the two? -- Roentgenium111 ( talk) 23:38, 3 August 2010 (UTC)
What's this table doing in the article? Most of the planets in there have masses comparable to Jupiter and are probably NOT terrestrial planets! —Preceding
unsigned comment added by
131.111.8.102 (
talk)
11:47, 21 January 2008 (UTC)
Planet.....Perhelion.....Average......Aphelion
Name ......Irradiance...Irradiance...Irradiance
Mars .............52.45%...43.11%....36.06%
HD 160691 b....103.07%....78.37%....61.59%
HD 125612 b....213.56%....79.47%....41.13%
HD 28185 b.......93.69%....81.03%....70.77%
HD 190228 b....262.13%....85.17%....41.65%
Gliese 876 c...162.61%....86.65%....53.73%
HD 188015 b....120.50%....87.06%....65.83%
Gl 581 g.........89.13%....89.13%....89.13%
HD 16175 b.....548.49%....92.20%....36.47%
HD 100777 b....237.79%....97.40%....52.66%
Earth............103.43%...100.00%....96.74%
HD 38083 b.....290.32%...101.06%....50.83%
HD 108874 b....119.47%...103.33%....90.25%
HD 155358 c....155.02%...105.26%....76.11%
HD 142415 b....425.29%...106.32%....47.25%
HD 20367 b.....185.73%...110.12%....72.79%
HD 82943 b.....182.79%...111.50%....75.03%
HD 221287 b....136.29%...115.36%....98.90%
HD 45364 b.....167.83%...116.07%....85.02%
HD 92788 b.....221.33%...117.95%....73.13%
HD 153950 b....329.92%...143.71%....80.04%
HD 69830 d.....166.74%...144.22%...125.96%
Venus............193.93%...191.30%...188.73%
I am for serious amendments or deletion of the section.
24.78.172.60 (
talk)
18:13, 11 July 2011 (UTC)
![]() | It has been suggested that this section be
split out into another page titled
Earth analog. (
Discuss) |
I suggest that the most Earth-like table be split to Earth analog, since that is what the table is about, the most Earth-like analog. 70.24.248.23 ( talk) 23:25, 26 November 2011 (UTC)
I see one more issue. Earth analog is about planets which have multiple similarities to earth. terrestrial is about planets with the composition of earth. how about earth-sized planets? since we just found 2, and dont know their composition, and know they are not earth analogs, should we have an article simply on earth sized planets? or is this too detailed? Note that some articles like the new Kepler-20f planet, link to terrrestrial, when we dont know yet that they are terrestrial. or do we? Mercurywoodrose ( talk) 05:06, 21 December 2011 (UTC)
hello world. I am looking for an extrasolar planet thats in its habitable zone. i know there has to be one out there somewhere. most people think that a habitable zone is much smaller than it really is. in truth there are many variables that can decide how large the habitabloe zone is. such as atmospheric composition, planetary comositon, and type of star if the planet has a largly co2 based atmosphere than it will be farther than a planet without as much co2. a planet with an extremely bright star will be farther than a planet with a dim star. Also a planet with a lot of carbon in the suface will absorb more sunlight, and heat, than a planet without it. 206.78.212.250 ( talk) 19:32, 26 August 2011 (UTC)Robert Moore
What is the density of 'rock' (as used in astronomy)? -- JorisvS ( talk) 12:51, 12 September 2012 (UTC)
Shouldn't there be at least some discussion of CoRoT-7b and Kepler-10b in this section, for which we actually have density measurements that imply they are in fact terrestrial. At present it looks like the focus is on a bunch of RV-detected worlds that may or may not be terrestrial in nature. 46.126.76.193 ( talk) 22:51, 8 October 2012 (UTC)
Rocky Planet Density Equation :
Density of Rocky Planets = (1+Pi) x 10^-9 * Radius^3 + (1 + sqrt 2) x 10^-1 * Radius + 2900 kg/m^3 The Radius must be in kilometers. The first term is the Tri-Axial coefficient of compression which does not really kick-in until the planet get big. The second term is the Uni-Axial coefficient of compression caused by the planets self gravity. The third term varies with the average composition of the near surface materials. For the Moon and Earth, it is 2900 because of the mixture of granite and basalt in the upper 400 km. For Venus the constant is lower (2657.05 kg/m^3) because Venus is very hot (expanded), and is dominated by low density rocks near the surface. For Mars the constant is higher (2941.05 kg/m^3) because Mars is cold (contracted), and its surface is dominated by (red ) Iron rich basalt. Note that the third term can be changed for various groups of planets. For Planets dominated by Ice, especially very thick ice, the third term might be between 900 and 1100 Kg/m^3, or, for a planet like Mercury that is dominated by Iron, the constant, third term, will be much higher. The third term can actually tell you a lot about a planets composition.
Michael W. Clark Golden, Colorado, USA — Preceding unsigned comment added by 63.225.17.34 ( talk) 17:11, 22 December 2015 (UTC)
terrestrial planets include the folowing....... Mercury, Earth,Mars, and Venus
—Preceding unsigned comment added by Setoguchi16 ( talk • contribs) 07:05, 17 December 2007 (UTC)
For Rocky Planets with Compressed Density, one can us the Rocky Planet Density Equation. Density ( Rocky Planets) = ( 1+Pi ) X 10^ -9 X R^3 + ( 1+ SQRT 2 ) X 10^ -1 X R + 2900 kg/m^3 The First Term is the Tri-Axial Coefficient of Compression. The second Term is the Uni-Axial (Gravitational-Vertical) Coefficient of Compression. The Third term is the Average Density of the Earth and Moon Crustal Materials. The third term can be changed to changing material conditions. For Example. Venus' third term is 2657.05 ( Hot Granitic material ), or Mars' third term is 2941.05 ( Cold Basaltic material ). Ice Planets would have a third term similar to Earth's water Ice, between 900 and 1,000.
The Beauty of this equation is that you only need to know the Radius, and what material is in the crust to obtain a useful Density. All of the other calculations for Volume, Mass, Surface Gravity,Escape Velocity, etc. only require Density, and Radius, and the Density is now just a function of the Radius also. Mike Clark, Golden, Colorado. 63.225.17.34 ( talk) 17:21, 16 September 2016 (UTC)
I think a table of compressed and uncompressed densities of the 4 inner planets and the moon would make a nice addition to this page.
Object | mean density | uncompressed density |
---|---|---|
Mercury | 5.4 g/cm³ | 5.3 g/cm³ |
Venus | 5.2 g/cm³ | 4.4 g/cm³ |
Earth | 5.5 g/cm³ | 4.4 g/cm³ |
Moon | 3.3 g/cm³ | 3.3 g/cm³ |
Mars | 3.9 g/cm³ | 3.8 g/cm³ |
I haven't found an authoritative source for these numbers or a formula to relate the density, mass and uncompressed density. So far I've found this source http://geophysics.ou.edu/solid_earth/notes/planets.html#densities but I don't believe it is original.
This is my first Wikipedia addition. Please let me know if there are things I should do to tidy up the addition. I'm still in search of a good source for the uncompressed density calculation. The uncompressed density of Ceres was an assumption based on the trend of compressed to uncompressed densities as the mass decreased.
A planet is squeezed by its own gravity: the deeper layers are compressed by the weight of the overlying layers. This increases the density of the planet. The uncompressed density is the (lower) density that the planet would have if this gravitational squeezing did not occur. The reason one would want to estimate a planet's uncompressed density is that this gives a hint about what the planet is made of. A higher uncompressed density suggests a larger abundance of heavier elements such as iron. —Preceding unsigned comment added by 192.172.8.13 ( talk) 16:31, 17 January 2011 (UTC)
There must be a very simple formula for calculating the uncompressed density for a planet, from its Mass and Radius. So, I am surprised how different some of the estimates I have read online for the densities of the terrestrial planets are. — Preceding unsigned comment added by 86.129.207.191 ( talk) 09:21, 3 March 2017 (UTC)
Tamfang : "So far I've found this source http://geophysics.ou.edu/solid_earth/notes/planets.html#densities but I don't believe it is original." This link is dead. I'm just trying to work on this question in respect of a recent Arxiv paper on Mercury, and while I understand the concept, working out how to calculate it is much harder.
86.129.207.191 : "There must be a very simple formula for calculating the uncompressed density for a planet, from its Mass and Radius." No, that would be the BULK density, not the UNCOMPRESSED density. To calculate the uncompressed density, you'd need to have a model of the structure of the planet (distance from centre versus material), and an equation of state for those material - how much they compress under different pressures.
These class-notes from an astronomy course (by @plutokiller, even!) give some useful information buried in a lot of maths. http://web.gps.caltech.edu/~mbrown/classes/ge131/notes/djs08.pdf He's more concerned with the upper end of planetary masses, where the transition between thin vapour and metal is a little more drawn out, and it's relation to compact object (neutron stars, white dwarfs), but it is relevant. Probably a lot more relevant stuff in the rest of the class notes at http://web.gps.caltech.edu/~mbrown/classes/ge131/.
From https://www.fossilhunters.xyz/solar-nebula/uncompressed-density-and-bulk-planetary-compositions.html, someone else is thinking on very much the same lines as me : "However, pressure corrections to uncompressed density estimates require detailed knowledge of the internal planetary structure (i.e., details of core, mantle and crust structures), equations of state of the various materials that make up the planet (e.g. bulk moduli and their pressure derivatives) and the thermal structure of the planet." Unfortunately, this appears to be culled from somewhere else, making reference to "Stacey [30] reviewed the question of the equations of state of planetary materials and estimated an internally consistent set of uncompressed densities for the terrestrial planets.", but then gives no list of references. I think this may be a reference to " http://iopscience.iop.org/article/10.1088/0034-4885/68/2/R03/pdf" but I don't have access to that journal, so I can't follow it up any further. I'll look back to the article to see if there is anything referenced that I can add.
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 |
I am doing a project in school. We have to design a planet and the planet that my partner and i designed is completly water except for a few scattered volcanoes. Would animals like penguins and walruses be able to survive on a planet like this? Please answer ASAP!!!!!
What is the role that impact cratering had in history on the formation of terrestrial planets? —The preceding unsigned comment was added by 149.169.207.32 ( talk • contribs) on 00:17, 1 September 2006.
I don't think the use of this term is appropriate. The planemo article says hardly anyone uses it, so I think it is not right here. Also, why apply the term to only two of the moons, all "rounded bodies" qualify for the term. HarryAlffa ( talk) 18:16, 1 June 2009 (UTC)
In the section on extrasolar planets, the term "fusing star" is used and linked to another article ("Solar Nucleosynthesi", I think?). The other article does not explain the term "fusing star". I recommend changing the term "fusing star" for the title of the other article. -- Eddylyons ( talk) 23:30, 14 August 2009 (UTC)
Why does the first sentence of the article regard 'inner planet' as an synonym of 'terrestrial planet'? The fact that all terrestrial planets in our solar system are inner planets (that is, planets between the sun and de asteroid belt) says nothing about the situation in other planetary systems. As a result, the current article is wrong to suggest that alle terrestrial exo-planets are inner planets too. DaMatriX ( talk) 22:49, 15 December 2009 (UTC)
-- MathFacts ( talk) 06:30, 20 December 2009 (UTC)
Under Terrestrial_worlds, I believe any required wiggle room can be changed by changing "referred to as geophysical planets" to "referred to as geophysical worlds", if need be. Though I am going to try and think about this for a day. I also did not realize the solar terrestrial planets section contained a discussion about worlds when I made my first edit. Hmm walked into a can of worms? -- Kheider ( talk) 10:01, 21 December 2009 (UTC)
I've removed the following section from the article:
It is not uncommon for natural satellites that are in hydrostatic equilibrium to be referred to as terrestrial worlds. [1] The seven moons that are occasionally referred to as terrestrial worlds are: Earth's Moon, Io, Europa, Ganymede, Callisto, Titan, and Triton. [1] Planetary scientist Alan Stern has informally suggested such bodies can be referred to as geophysical planets. [2] There are 19 known satellites that meet the geophysical requirement of a planet, though since they orbit planets they cannot be considered planets themselves. The question is should some of these objects be considered as evolved icy bodies rather than terrestrial bodies? Titan looks and behaves more like Earth than any other body in the Solar System. [3] Titan is known to have stable pools of liquid on the surface. [3]
Titan showing surface and atmospheric details Volcanos on Io constantly re-surface the satellite Europa is believed to have a subsurface ocean False color image of Ganymede A cloud over the limb of TritonIn addition, Earth's moon and Jupiter's satellites Io and Europa can also be regarded as terrestrial worlds. [1] Io and Europa have mainly rocky compositions despite forming beyond the frost line. This may be because the region of the circum-Jovian disc in which they formed was kept too warm by radiation from the proto-Jupiter to contain large quantities of icy material.
As mentioned on Kheider's talk page, this appears to be putting too much weight on an unofficial, informal forum post, and needs much more in the way of verifiable sourcing. At present, it is a case of undue weight (unless, again, more sources are provided. I'd suggest that the best course is to develop the text here, rather than in the artcile, until agreement is reached as to the best approach. -- Ckatz chat spy 10:28, 21 December 2009 (UTC)
Dr. James Schombert has also stated, (at bottom of page) "Large amounts of outgassing have drained the inner moons, Io and Europa of their icy materials making them rich in rocky materials." I agree that we need to make it clear that the concept is inherently ambiguous nor does it have an official definition. When does something go from rocky to icy? How do you define Earth-like? In the pre-voyager era, Earth-like pretty much meant non- gas giant since we knew almost nothing about the large moons of the solar system. -- Kheider ( talk) 21:12, 23 December 2009 (UTC)
Exo- water planets could result from inward planetary migration and originate as protoplanets that formed from volatile ice-rich material beyond the snow-line but that never attained masses sufficient to accrete large amounts of H/He nebular gas. Water worlds might be thought of as a bigger and hotter version of Jupiter's Galilean moons. -- Kheider ( talk) 01:56, 24 December 2009 (UTC)
{{
cite web}}
: External link in |author=
(
help)
This article claims the moon lacks an iron core. But if I remember right... http://en.wikipedia.org/wiki/Moon#Internal_structure Yes, even elsewhere on Wikipedia it is noted to have "an iron-rich core". Which is it? Or is there some threshold for "made of iron" that the moon's "iron-rich" core not actually cross? Someone who knows more should correct it. Thanks, NickRinger ( talk) 17:25, 4 May 2011 (UTC)
According to that table, Gliese 581c is smaller than 581e. But the latter is much lighter AND closer to the star (roughly implying higher density), so shouldn't 581e be the smaller one of the two? -- Roentgenium111 ( talk) 23:38, 3 August 2010 (UTC)
What's this table doing in the article? Most of the planets in there have masses comparable to Jupiter and are probably NOT terrestrial planets! —Preceding
unsigned comment added by
131.111.8.102 (
talk)
11:47, 21 January 2008 (UTC)
Planet.....Perhelion.....Average......Aphelion
Name ......Irradiance...Irradiance...Irradiance
Mars .............52.45%...43.11%....36.06%
HD 160691 b....103.07%....78.37%....61.59%
HD 125612 b....213.56%....79.47%....41.13%
HD 28185 b.......93.69%....81.03%....70.77%
HD 190228 b....262.13%....85.17%....41.65%
Gliese 876 c...162.61%....86.65%....53.73%
HD 188015 b....120.50%....87.06%....65.83%
Gl 581 g.........89.13%....89.13%....89.13%
HD 16175 b.....548.49%....92.20%....36.47%
HD 100777 b....237.79%....97.40%....52.66%
Earth............103.43%...100.00%....96.74%
HD 38083 b.....290.32%...101.06%....50.83%
HD 108874 b....119.47%...103.33%....90.25%
HD 155358 c....155.02%...105.26%....76.11%
HD 142415 b....425.29%...106.32%....47.25%
HD 20367 b.....185.73%...110.12%....72.79%
HD 82943 b.....182.79%...111.50%....75.03%
HD 221287 b....136.29%...115.36%....98.90%
HD 45364 b.....167.83%...116.07%....85.02%
HD 92788 b.....221.33%...117.95%....73.13%
HD 153950 b....329.92%...143.71%....80.04%
HD 69830 d.....166.74%...144.22%...125.96%
Venus............193.93%...191.30%...188.73%
I am for serious amendments or deletion of the section.
24.78.172.60 (
talk)
18:13, 11 July 2011 (UTC)
![]() | It has been suggested that this section be
split out into another page titled
Earth analog. (
Discuss) |
I suggest that the most Earth-like table be split to Earth analog, since that is what the table is about, the most Earth-like analog. 70.24.248.23 ( talk) 23:25, 26 November 2011 (UTC)
I see one more issue. Earth analog is about planets which have multiple similarities to earth. terrestrial is about planets with the composition of earth. how about earth-sized planets? since we just found 2, and dont know their composition, and know they are not earth analogs, should we have an article simply on earth sized planets? or is this too detailed? Note that some articles like the new Kepler-20f planet, link to terrrestrial, when we dont know yet that they are terrestrial. or do we? Mercurywoodrose ( talk) 05:06, 21 December 2011 (UTC)
hello world. I am looking for an extrasolar planet thats in its habitable zone. i know there has to be one out there somewhere. most people think that a habitable zone is much smaller than it really is. in truth there are many variables that can decide how large the habitabloe zone is. such as atmospheric composition, planetary comositon, and type of star if the planet has a largly co2 based atmosphere than it will be farther than a planet without as much co2. a planet with an extremely bright star will be farther than a planet with a dim star. Also a planet with a lot of carbon in the suface will absorb more sunlight, and heat, than a planet without it. 206.78.212.250 ( talk) 19:32, 26 August 2011 (UTC)Robert Moore
What is the density of 'rock' (as used in astronomy)? -- JorisvS ( talk) 12:51, 12 September 2012 (UTC)
Shouldn't there be at least some discussion of CoRoT-7b and Kepler-10b in this section, for which we actually have density measurements that imply they are in fact terrestrial. At present it looks like the focus is on a bunch of RV-detected worlds that may or may not be terrestrial in nature. 46.126.76.193 ( talk) 22:51, 8 October 2012 (UTC)
Rocky Planet Density Equation :
Density of Rocky Planets = (1+Pi) x 10^-9 * Radius^3 + (1 + sqrt 2) x 10^-1 * Radius + 2900 kg/m^3 The Radius must be in kilometers. The first term is the Tri-Axial coefficient of compression which does not really kick-in until the planet get big. The second term is the Uni-Axial coefficient of compression caused by the planets self gravity. The third term varies with the average composition of the near surface materials. For the Moon and Earth, it is 2900 because of the mixture of granite and basalt in the upper 400 km. For Venus the constant is lower (2657.05 kg/m^3) because Venus is very hot (expanded), and is dominated by low density rocks near the surface. For Mars the constant is higher (2941.05 kg/m^3) because Mars is cold (contracted), and its surface is dominated by (red ) Iron rich basalt. Note that the third term can be changed for various groups of planets. For Planets dominated by Ice, especially very thick ice, the third term might be between 900 and 1100 Kg/m^3, or, for a planet like Mercury that is dominated by Iron, the constant, third term, will be much higher. The third term can actually tell you a lot about a planets composition.
Michael W. Clark Golden, Colorado, USA — Preceding unsigned comment added by 63.225.17.34 ( talk) 17:11, 22 December 2015 (UTC)
terrestrial planets include the folowing....... Mercury, Earth,Mars, and Venus
—Preceding unsigned comment added by Setoguchi16 ( talk • contribs) 07:05, 17 December 2007 (UTC)
For Rocky Planets with Compressed Density, one can us the Rocky Planet Density Equation. Density ( Rocky Planets) = ( 1+Pi ) X 10^ -9 X R^3 + ( 1+ SQRT 2 ) X 10^ -1 X R + 2900 kg/m^3 The First Term is the Tri-Axial Coefficient of Compression. The second Term is the Uni-Axial (Gravitational-Vertical) Coefficient of Compression. The Third term is the Average Density of the Earth and Moon Crustal Materials. The third term can be changed to changing material conditions. For Example. Venus' third term is 2657.05 ( Hot Granitic material ), or Mars' third term is 2941.05 ( Cold Basaltic material ). Ice Planets would have a third term similar to Earth's water Ice, between 900 and 1,000.
The Beauty of this equation is that you only need to know the Radius, and what material is in the crust to obtain a useful Density. All of the other calculations for Volume, Mass, Surface Gravity,Escape Velocity, etc. only require Density, and Radius, and the Density is now just a function of the Radius also. Mike Clark, Golden, Colorado. 63.225.17.34 ( talk) 17:21, 16 September 2016 (UTC)
I think a table of compressed and uncompressed densities of the 4 inner planets and the moon would make a nice addition to this page.
Object | mean density | uncompressed density |
---|---|---|
Mercury | 5.4 g/cm³ | 5.3 g/cm³ |
Venus | 5.2 g/cm³ | 4.4 g/cm³ |
Earth | 5.5 g/cm³ | 4.4 g/cm³ |
Moon | 3.3 g/cm³ | 3.3 g/cm³ |
Mars | 3.9 g/cm³ | 3.8 g/cm³ |
I haven't found an authoritative source for these numbers or a formula to relate the density, mass and uncompressed density. So far I've found this source http://geophysics.ou.edu/solid_earth/notes/planets.html#densities but I don't believe it is original.
This is my first Wikipedia addition. Please let me know if there are things I should do to tidy up the addition. I'm still in search of a good source for the uncompressed density calculation. The uncompressed density of Ceres was an assumption based on the trend of compressed to uncompressed densities as the mass decreased.
A planet is squeezed by its own gravity: the deeper layers are compressed by the weight of the overlying layers. This increases the density of the planet. The uncompressed density is the (lower) density that the planet would have if this gravitational squeezing did not occur. The reason one would want to estimate a planet's uncompressed density is that this gives a hint about what the planet is made of. A higher uncompressed density suggests a larger abundance of heavier elements such as iron. —Preceding unsigned comment added by 192.172.8.13 ( talk) 16:31, 17 January 2011 (UTC)
There must be a very simple formula for calculating the uncompressed density for a planet, from its Mass and Radius. So, I am surprised how different some of the estimates I have read online for the densities of the terrestrial planets are. — Preceding unsigned comment added by 86.129.207.191 ( talk) 09:21, 3 March 2017 (UTC)
Tamfang : "So far I've found this source http://geophysics.ou.edu/solid_earth/notes/planets.html#densities but I don't believe it is original." This link is dead. I'm just trying to work on this question in respect of a recent Arxiv paper on Mercury, and while I understand the concept, working out how to calculate it is much harder.
86.129.207.191 : "There must be a very simple formula for calculating the uncompressed density for a planet, from its Mass and Radius." No, that would be the BULK density, not the UNCOMPRESSED density. To calculate the uncompressed density, you'd need to have a model of the structure of the planet (distance from centre versus material), and an equation of state for those material - how much they compress under different pressures.
These class-notes from an astronomy course (by @plutokiller, even!) give some useful information buried in a lot of maths. http://web.gps.caltech.edu/~mbrown/classes/ge131/notes/djs08.pdf He's more concerned with the upper end of planetary masses, where the transition between thin vapour and metal is a little more drawn out, and it's relation to compact object (neutron stars, white dwarfs), but it is relevant. Probably a lot more relevant stuff in the rest of the class notes at http://web.gps.caltech.edu/~mbrown/classes/ge131/.
From https://www.fossilhunters.xyz/solar-nebula/uncompressed-density-and-bulk-planetary-compositions.html, someone else is thinking on very much the same lines as me : "However, pressure corrections to uncompressed density estimates require detailed knowledge of the internal planetary structure (i.e., details of core, mantle and crust structures), equations of state of the various materials that make up the planet (e.g. bulk moduli and their pressure derivatives) and the thermal structure of the planet." Unfortunately, this appears to be culled from somewhere else, making reference to "Stacey [30] reviewed the question of the equations of state of planetary materials and estimated an internally consistent set of uncompressed densities for the terrestrial planets.", but then gives no list of references. I think this may be a reference to " http://iopscience.iop.org/article/10.1088/0034-4885/68/2/R03/pdf" but I don't have access to that journal, so I can't follow it up any further. I'll look back to the article to see if there is anything referenced that I can add.