Celestia Forums

Hello, you guys remember me right? heh.

A few things have been troubling me lately about Mars. After reading the marvelous fringe-science articles on the mars Tidal Model and the Exploded Planet Hypothesis I really got to wondering just how Mars could have been habitable following standard theory, here's what puzzles me.

Presuming the sun was indeed slightly less luminous back in the day, say 3 billion years ago when Mars supposedly was warmer and wetter. How is it then that Mars wasn't a frozen ice-ball? If we assume that it has always had about 10% of Earth's Mass and if we presume then that it had a molten core and vulcanism wouldn't most of the atmosphere it had be due to volcanic outgassing? and wouldn't most of that be lost to space over time? Or do we assume that Mars at one point had a much thicker atmosphere and slowly lost it to space? I guess I'm just not clear on how Mars could have been more Lush in the past Solar System than it is today considering the Suns previously less luminous state.

Also can someone explain to me the actual color of the Martian Sky? I've seen Mars atmosphere colored as blue, yellow, grey, green and pink. Just which is it? does it depend on who has control of the color correction when the photos come out? I'd always assumed that it would be a deep blue/grey due to the thin atmosphere, but every photo we get from NASA shows a dust-strewn sky, where am I going wrong here?

Anyway I was just feeling a little confused here, I'd love to hear any explinations to set me straight, cheers.

A thicker atmosphere in the past would have been more of a significant factor than the less luminous sun. It traps in the heat. Think of a cold sunny day. Its still warm inside a parked car because it traps heat.

I've seen the martian sky described as many different colors (never green though). I don't see any reason to believe its a different color than the faded pink color in the real-color images from the rovers. Here on Earth, when I take a horizon picture that includes the sky, my camera doesn't change the sky to green. It still looks pretty accurate, as long as the exposure doesn't lighten or darken it. But even if it does, it doesn't change its color, just its intensity. One thing for sure, the Martian sky is black at night.

You have to remember that mars atmosphere is motsly CO2, so if it was thicker the green house effect was very important thre...

A dark salmon pink seems to be about right for the Martian sky. The early Viking pictures showed it blue because they got their colour calibration wrong, and there are a number of false-colour sunset images out there that that add to the confusion.
If there were no dust aloft in the Martian atmosphere, the sky would be dark blue with paler blue around the horizon - but all those dustdevils and storms inject a lot of fine dust into the atmosphere, which takes ages to settle again. The bulk of the scattered light therefore comes from dust "fines" rather than carbon dioxide molecules.

As to the temperatures in the past - it doesn't take a huge carbon dioxide partial pressure to maintain liquid-water pressures and temperatures on Mars, even with a young Sun. Loss to space because of ballistic "evaporation" of CO2 from the thermosphere would actually be pretty slow even for a warm Mars - the big players in disposing of the early carbon dioxide are said to be large impacts (blasting masses of air up to escape velocity) and weathering processes (binding CO2, which was subsequently not replaced because vulcanism failed).

Grant

ahha so my mind is a little clearer now, I rather like the salmon-pink color of the Martian Sky, though I had become somewhat confused as to just what it was really like. As for the loss of CO2 I can understand that, with no replinishment possible the atmosphere would slowly dwindle away and it may not have been all that heavy to begin with eh?

Also did you hear this nonsense about the beagle-2 report not being released? wow that really inspires trust eh? ^_^ Cheers.

It makes sense what Grant says, that the color of the sky has more to do with dust in the atmosphere than the diffusion of light. Here on Earth, dirt is brown, and on windy days in the Sacramento Valley, the sky is brown too.

I wonder... if you were standing on top of Olympus Mons at high noon, could you see stars in the sky?

Actually your point about day at the top of Mount Olympus is quite intriguing. If you consider the extraordinary conditions on Mars, the highly elliptical orbit and the extreme changes in temperature and atmospheric pressure with elevation. As I recall the pressure can varry between 9 millibars at the bottom of Hellas Planita to 1 millibar atop Mons Olympus. I also hear that the temps can range from 140K at the poles in winter to 300K at ground-level at the equator.

That being said the very low pressure atop the mountains of Tharsis could produce some very interesting daytime sights, I wonder if its above the dust level? or is the dust scattered evenly throughout the entire atmosphere? I also remember that the Martian sky gets more blue closer to the sun, due to its low density. it would be interesting to see what its like, although in our lifetimes thats likely not possible, hard enough to get people in LEO much less off this blue rock, heh.

Oh well I still like Mars dead or not ^_^ Thanks for the replies