Talk:Terrestrial planet

From Wikipedia, the free encyclopedia

WikiProject Solar System
Solar System Portal

This article is within the scope of the Solar System WikiProject, a collaborative effort to improve Wikipedia's coverage of the Solar System.
Start This article has been rated as Start-Class on the assessment scale.

Contents

[edit] pluto

So what about Pluto? It's clearly not a gas giant. So is it a terrestrial planet? Or is it a third class? Or do we not know?

Well, it's not listed in the article text but it's present in the image, along with a bunch of other bodies that are mainly ice rather than silicate (and also some that have active hydrospheres, directly contradicting the article text). I don't know the answer myself but we should either find out what the official line is or we should mention that there's ambiguity. Bryan 18:21, 28 Mar 2005 (UTC)
Pluto is, at the moment, considered a planet, and would technically be designated as a terrestial planet. However, there's so much debate over Pluto's status, especially since Sedna was discovered, that I think Bryan's idea of just mentioning an ambiguity is best. Also, I was thinking of maybe adding a list of exo-terrestial-planets, too, if nobody objects? So far, I have:
55 Cancri A e 14 ME
Gliese 777 A c 18 ME
mu Arae d 14 ME
GJ 436 b 21 ME
PSR 1257+12 A .020 ME
PSR 1257+12 B 4.3 ME
PSR 1257+12 C 3.9 ME
Gliese 876 d 6-8 ME.
I'm not sure how complete this list is, as I took these from Wikipedia's "list of extrasolar planets" and then added Gliese 876 d, which despite being mentioned on most exoplanet-related pages as the lowest-mass non-pulsar exoplanet, is not listed on the "list of extrasolar planets page." Whew. Long sentence, that. ZelmersZoetrop
Pluto (and anything that far out) would probably be better classified as a 'Kuiper Object' as technically the Kuiper Belt starts from inside Neptune's orbit. ref-Kuiper_belt.
Although the label 'Minor Planet' is adequate, i would hesitate to call Pluto 'Terrestrial' in the truest sense...
Ambiguity, as you say is probably the best course for now :) Grey Area 08:44, 29 July 2005 (UTC)

[edit] Conflicting data?

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!!!!!

See planetary habitability to begin with. I think that page will have the most data for you.
If your planet is only going to have volcanic islands then its probably not tectonically active, as this is the main continent building process. This means low biodiversity and a lesser chance that animals like penguins and walruses would arise. But nothing is impossible with a hypothetical planet. Perhaps in shallow pools surrounding your islands multi-cellularity arose, and after that the sky's the limit. Perhaps you can revisit the model and add in some continents? Marskell 13:50, 4 April 2006 (UTC)

[edit] Impact Cratering

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'm not sure I understand the question. Cratering itself doesn't affect the formation much; it's usually just used as a yardstick to measure how active the geology of a planet or moon is (if it's geologically active, it recycles its surface material, reducing the number of visible craters; if it was active but then stopped being so, the crater density can give you a rough idea of how long ago this happened).
The material that's delivered in the process of bombardment is, however, important, as it's how a lot of the volatiles posessed by the inner planets got here as the solar system was forming (how much this changed the amount of volatiles is an open question, though). --Christopher Thomas 05:14, 1 September 2006 (UTC)

[edit] Intrinsic Definition ?

In the good old days, when I first learned science, all living things were either animals or plants, and there were four terrestrial planets, four gas giants, plus Pluto with a question mark. Those old dichotomies were clearly inadequate. If the definition of terrestrial planet is intrinsic, i.e., depends only on the physical characteristics of the planet itself, then the Moon must be called a terrestrial planet. The definition does not make it clear whether having a rocky surface is a requirement. What if a planet is almost all rock and iron entirely covered with a few miles of ice? What if it's rock and iron, covered with an inpenetrable atmosphere of hydrogen and helium? What about Titan, which is a planet by any intrinsic definition? And what about Io? I suspect that there will be lots of overlapping classes of planets defined in the next generation, but that consensus on this issue will not soon be achieved. Vegasprof 11:19, 30 April 2007 (UTC)

[edit] Is Ceres a terrestrial body?

Judging by its low density (2.0g/cm3, Ceres should really be called an ice dwarf and not a terrestrial (dwarf) planet.

That density is much lower than that of the Moon, or Jupiter's inner large moons Io and Europa. If Ceres is a terrestrial (dwarf) planet, what about the Moon, Io and Europa??

luokehao

[edit] Terrestrial planets

terrestrial planets include the folowing....... Mercury, Earth,Mars, and Venus so by by now and so long farewell aveters and goodbye!!!!! —Preceding unsigned comment added by Setoguchi16 (talk • contribs) 07:05, 17 December 2007 (UTC)

[edit] Most Earthlike exoplanets

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)

[edit] Uncompressed Densities

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.