Atmosphere Closest to Earth's?

[PJay_A]

<p>Which planet or moon's atmosphere is closet to our own in terms of chemical make-up and density?</p><p>My guess is Titan because of its nitrogen and I would guess it's pressure is closest, although it's multiples times that of earth which is far closer than the 100 times greater pressure of Venus and the 1/100th thinner than ours as Mars is.</p><p>Also, has oxygen been detected anywhere besides earth? I think I read somewhere that Mercury and Ganymede have a thin oxygen atmosphere. Is that true?&nbsp;</p>

 

[hal9891]

In high altitude (50km IIRC) Venusian atmosphere has the same pressure and temperature as Earth's atmosphere at sea level, though it has a very different chemical makeup.<br /> <div class="Discussion_UserSignature"> <div style="text-align:center"><font style="color:#808080" color="#999999"><font size="1">"I predict that within 100 years computers will be twice as powerful, 10000 times larger, and so expensive that only the five richest kings of Europe will own them"</font></font><br /></div> </div>

 

[neilsox]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>In high altitude (50km IIRC) Venusian atmosphere has the same pressure and temperature as Earth's atmosphere at sea level, though it has a very different chemical makeup. <br />Posted by hal9891</DIV><br />Fortunately the sulpheric acid is mostly at a lower altitude than the cool air. Plants can possibly do photosythesis at an altitude where balloons are practical above Venus. The atmosphere of Venus is about 1% free&nbsp;nitrogen and the plants can make some free oxygen from the carbon dioxide, which is about 98% of the Venus atmosphere. There are several threads about terriforming Venus, but so much energy is required, we may never succeed with colonies even at the poles of Venus on the surface.&nbsp;&nbsp; Neil

 

[baulten]

<p>Titan has the closest density and makeup, being about 1.5x Earth's atmospheric pressure at the surface and primarily nitrogen, but it lacks oxygen and has a lot of toxic hydrocarbons in it.</p><p>Venus's atmosphere, I believe, has roughly the same amount of nitrogen and oxygen that Earth's does.&nbsp; It's just that because of the massive amount of CO2, Sulphuric acid, etc. that that nitrogen and oxygen make up less than 1% of the total atmosphere. Like Hal9891 said, it's about Earth pressure and temperature at 50km above the surface.</p><p>Mars is nearly all carbon dioxide and extremely thin.&nbsp; Not much of a match.</p><p>Jupiter's moons have mostly oxygen atmospheres from the interaction with the Jovian magnetosphere, or something like that.&nbsp; I can't remember exactly how it works, but I think that the magnetosphere liberates some oxygen from the mostly ice moons, given them a tenous oxygen atmosphere.&nbsp;&nbsp;</p><p>Mercury has an atmosphere composed mostly of trace gases.&nbsp; I can't remember the makeup.</p><p>Obviously the gas giants are different than Earth's, and as far as I know none have a "habitable zone" like the upper Venusian atmosphere. </p>