Talk:Hellas Planitia

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Basin extent[edit]

and its eastern point stretches farther than 7000 km across

I replaced the above misleading description with the following:

, extends about 2100 km east to west, and its debris field could be interpereted as extending about 6000 km across

The 6000 km is my interpretation from the graph shown on the NASA page, there is no text to back it up, and someone could interpret the raised debris field extending anywhere from from 5000 to 7000 km, I guess.

Checked http://rst.gsfc.nasa.gov/Sect19/Sect19_12.html . The graph and page text doesn't show enough to be sure that's the width of the entire debris field, and "could be interpreted as" is weasel words, so I'm going to cut mention of the debris field size until we have a definite source on debris field width. Couldn't find one by Googling. (Mojei (talk) 15:38, 8 October 2009 (UTC))
Hello I sited that source. 7,000 is no where near 2,100. And I found no websites showing the actual diameter. So I believe Hellas Basin is alot bigger than the SPA. I could be wrong, but are u measuring the basin floor? Here is a graph comparing the sizes within the rims. Is it 2100 or 7000? I would really like to know thanks. http://upload.wikimedia.org/wikipedia/en/7/72/Size234.gif
Also check out my user name for correction because judging the diameter does not mean you measure the height.
--Murriemir (talk) 05:16, 12 June 2008 (UTC)

The Brittanica cite here has:

Hellas measures about 7,000 km (4,400 miles) across, including the broad elevated ring surrounding the depression, and 8 km (5 miles) deep.

which includes the phrase "including the broad elevated ring surrounding the depression". This is consistent with the NASA graph, but omits the size of the basin itself (what the reader sees as the blue region and probably considers to be the basin). Maybe someone could improve my writing and improve the precision? It seems difficult to define extent for such a feature, at what elevation does one measure it: At the zero datum? At the debris "rim" height? -84user (talk) 12:47, 9 June 2008 (UTC)

Murriemir, (I indented your comment above) I do not know how a basin is defined, I used the NASA cite (for "Planitia" which means plain) and tried to reconcile it with Brittanica. I guess it depends on where scientists believe the rim of Hellas is. Maybe it is buried under the debris? Or did all the debris escape and what's there now is the elevated rim? I just do not know. I posted this query on Wikipedia talk:WikiProject Solar System asking how planetary scientists define basin sizes. There are some wikipedia articles on impact basins with inconsistent sizes. It seems we should give as many known figures as possible, such as basin floor, elevated rim, debris outer edge (if any), outer concentric ring. -84user (talk) 19:36, 12 June 2008 (UTC)

Well, if craters like shiva cant be identified as impact basins why can the moons? Anyways on Earth the scientists identify the basins by having foreign composite material. The rules seem to be different in space.--Murriemir (talk) 20:43, 13 June 2008 (UTC)

I am running into this problem of basin size in the Geology of Mars article. As noted above, diameter seems to depend of whether the rim materials are included or just the central plain (Planitia), which corresponds roughly to the basin floor. Schaffman (talk) 10:50, 16 September 2010 (UTC)

Atmospheric Pressure[edit]

I don't think this part is correct:

and above the triple point of water, suggesting that the liquid phase would be transient (would evaporate over time) if the temperature would rise above 0 °C (32 °F).[7]

the implication of the pressure being above the triple point of water is that liquid water can actually exist, that is, there is a range of temperatures within which water is liquid. It's not a very big range, maybe 10 degrees C (because the pressure isn't very much above the triple point), but this compares with most of the rest of the surface of Mars, for which the pressure is below the triple point (about 0.6 kPa). In the latter case, there is no temperature at which water will exist in equilibrium in the liquid phase. DuncanKitchin (talk) 05:27, 13 April 2009 (UTC)

Oh how convenient. The resolution of the basin in Google Earth (Mars) is lower then the surrounding terrain.98.165.6.225 (talk) 15:14, 3 June 2009 (UTC)

Red cr*p[edit]

How come that, according to the image in the article, Hellas Planitia is entirely red, yet in Google Mars it is white in color. I think, giving to the natural "color" of ice, the colors in the image provided are simply false. Please, replace it with the right one. 62.33.188.17 (talk) 21:52, 7 September 2009 (UTC)