New Mars Forums

Hi John!
    It's an interesting thought but I suspect atmospheric drag is going to be the show-stopper.
    If the scoop is kept high in the atmosphere, to minimise drag, your centre of gravity will be higher, meaning a lower orbital velocity and consequently slower scoop speed, and there's less gas available to scoop.
    On the other hand, if the scoop is allowed to operate in lower denser regions of the atmosphere, where intake of gases would be much greater, and your centre of gravity lower and orbital speed higher, the effects of drag on the whole structure would also be much greater.

    It seems likely to me you'd either have too little gas flow to make it worth the trouble, or so much drag you'd be using all the gas flow just to feed the station-keeping engines!

    Of course, I may be quite wrong about the whole thing and a mathematical evaluation might demonstrate it can be done. But I doubt it because it smacks a little too much of the old classic perpetual-motion-machine concept. Friction is a powerful dissipator of energy and entropy is hard to beat.
                                                      :bars:

An impressively simple system, Rik.
    I don't mean 'simple' as in dumb, I mean 'simple' as in fewer things to go wrong and therefore better. And it might well work - especially if something like your incremental risk strategy is employed.
    As I've said, I want it to work! If we can't have a real geologist on the surface, this would be a good surrogate.
    How much developmental lead-up time do you think it would take to get the AI system reliable enough to risk $300-400 million on?

You people have got to stop talking about all that delicious food like that! 
                I'm a kilo over and trying to cut back a little - gimme a break willya. ???

    Anyways, I hope all my American cousins had a great Thanksgiving. (I wonder what date the martian version will fall on?)
                                                   

Rik .. that's beautiful!   :laugh:
    Now I can't get the same picture out of my mind!     

Hi Atomoid.
    Sorry I haven't been back to this thread lately.
    There are many factors contributing to Earth's overall climate or average temperature, including the positions of the continents, the extent of volcanism, the amount of tectonic mountain building etc.

    The continental plates are constantly shifting; slamming together into supercontinents, then parting company, only to slam together once more.
    In doing this, they can assume positions which interfere with global oceanic currents and perhaps disrupt the transfer of heat from equatorial to polar regions. They can even trap an ocean at one of the poles, as is the case today with our Arctic Ocean, which is almost landlocked, or take up position right over a pole, as Antarctica has done. This shifting of land masses not only affects oceanic circulation, but also the movement of warm and cold air masses.
    Obviously volcanoes add CO2 and water vapour to the atmosphere, so periods of intense volcanic activity can add greatly to Earth's atmospheric greenhouse effect. There have been suggestions lately that large reservoirs of methane clathrates are stored over geological time in sediments on the sea floor. These reservoirs would be easily disturbed by volcanic and earthquake activity and perhaps suddenly release methane into the atmosphere in great quantities. Methane, as I'm sure you know, is a much more effective greenhouse gas than CO2, which means Earth could have been subjected to sudden 'spikes' in average temperature well above long-term averages.
    As continental plates collide and oceanic plates subduct, mountain ranges are pushed up. When this happens, the amount of erosion and 'weathering' of rock increases, which causes CO2 to be sequestered in carbonate rocks. This reduces the greenhouse effect and cools the planet.
    The way life responds to the changing conditions is also a factor. When continental positions and other factors created a perfect environment for lush vegetation during the carboniferous period, concentrations of CO2 fell, again producing a marked global cooling.

    The present climate on Earth is cold, with the global mean temperature being about 15 deg.C. Without the greenhouse effect of gases like water vapour, methane and CO2, of course, the global mean temperature would be much colder still, at -18 deg.C. So greenhouse gases are a good thing to have!
    But for most of the last 600 million years, the average temperature has been well above 17 deg.C, and for about half of that 600 million years it was 22 deg.C.
    It's actually very rare for Earth to be as cold as it is now for this long, and quite common for it to be 7 deg.C warmer. A big difference.

    When you look at the big picture, you see that a long-term increase in global temperatures is probably to be expected; aside from a few hiccups, the trend is likely to be up. And, as and when that happens, it will only be returning Earth to its customary much warmer conditions.
    This is one of the reasons I don't fret too much about the 0.7 deg.C rise in global temperatures purported to have occurred in the last 150 years. Agreed, if it's going to continue and/or accelerate, it will eventually cause problems we'll need to adapt to, so better to play safe with CO2 emissions. But I don't worry too much about a runaway greenhouse effect because, with Earth presently in the grip of a severe ice-age, we've got plenty of leeway before anything that dramatic happens! Plainly, if Earth's climatic balance were that fragile, those much warmer conditions in the past would have turned the place into another Venus a long time ago.

    There's a very interesting graph of Earth's average temperature since Pre-Cambrian times at the bottom of http://www.scotese.com/climate.htm]THIS WEB PAGE.
                                             
    I know this looks a bit off-topic, but I think understanding Earth's substantial climatic variations over geological time spans, even though the planet looks so stable from our limited human vantage point, is good preparation for considering how different Mars may have been in the past. And life hangs on tight once it gets a grip!

Excellent posts, Dickbill and Gennaro. Not just the content, which was entertaining and informative, but the way you guys express yourselves so well in a language which is not your own. Brilliant stuff!   :up:

    I have a copy of "The Fifth Miracle", by Dr. Paul Davies, which I think I've mentioned before. He deals with this type of discussion about complexity, entropy and information, and his treatment of these confirms, at least to me, how mystifying the rise of any life, let alone sentient life, really is.
    I don't think I have anything intelligent or original to add to what's been said already, except to say it's almost like Dr. Davies is struggling at the borderline between science and religion in his book. He traces the development of our understanding - or otherwise - of how complex carbon molecules might organise themselves into self-replicating structures and appears to come to the conclusion that we're a very long way from anything remotely resembling a coherent hypothesis.
    I understood most of the scientific concepts in the book but not all of them. However, there was no doubt that he believes we're missing something very important, something fundamental, in our efforts to explain life. He stops short of invoking God to help things along - he is a tenured scientist after all!  - but he seems to be implying that there may be something about life which science might never be able to explain.

    A great communicator, that Dr. Davies; he simplifies without 'dumbing down'.   

Well, GCNR, I understand where you're coming from here but, in my experience, getting annoyed with someone over a theoretical point rarely helps to get the point across.

    ERRORIST, let's forget about running tubes up the space elevator to geosynchronous orbit for a moment. There's something fundamental about liquids in tubes I think you are not aware of.

    Let's imagine something very straightforward and basic: I have a clear plastic tube 20 metres long. I place the tube in my swimming pool and jiggle it around to get all the air bubbles out, ensuring the whole tube is completely filled with water. O.K.? The tube is fully immersed in my pool and it's full of water.

    Now, I reach in and place an airtight watertight bung in one end of the tube, ensuring the tube remains submerged and full of water at all times.
    Next, I lift the sealed end of the tube out of the pool, again ensuring the open end stays beneath the surface and the tube remains filled with water.
    I then proceed to raise the sealed end of the tube higher and higher, by means of climbing a handy 15 metre step-ladder standing next to the pool. (Doncha just love these thought experiments?!  :;):  )

    Once the sealed end of the tube gets to a height of 10.3 metres above the surface of the pool water, something interesting happens. Even though we lift the sealed end higher still, the level of water inside the tube remains at 10.3 metres above the level of the pool water.
    As we move up the ladder, raising the sealed end of the tube to 15.3 metres above the water in the pool, we notice the water level inside the tube is now 5 metres below the bung.

    So, what's in the tube above the water? Effectively a vacuum. (I say "effectively" because it's not a 'hard vacuum'; there will be a tiny amount of water vapour present but, if you could get inside the tube, you'd need a pressure suit to survive.)
    So, why doesn't the vacuum suck the water up into the top 5 metres of the tube? The answer is that a vacuum doesn't actually 'suck' anything. Things like gases and fluids have to be pushed into a vacuum by the higher pressure in their vicinity.
    Holding up a column of water against the influence of gravity, inside a plastic tube, takes pressure. The pressure, in our example above, is supplied by the weight of Earth's atmosphere pushing down on the surface of the pool water. But that weight is completely balanced by the weight of just 10.3 metres of water inside the tube. The atmosphere can't push down hard enough to support a column of water any higher than this.

    Any clearer?   

O.K., I'm listening.
    You've got the two open ends close to sea-level, one end 10 feet higher than the other.

    Now, how high is the bend?
    What, exactly, are you trying to achieve?

It's always nice to be considered for things like this but I really don't have the computer-smarts for it. I'm so primitive it's as much as I can do just to post stuff here!
    I haven't even figured out how to do a custom-made icon or post a picture yet!          

[But soon ... I'll learn soon!! ]

CC:-

    Ha-ha !!   :laugh:
    I love it! It's cutting..very cutting, but I love it.   

No, I wasn't surprised about the stars not colliding when galaxies do; I read that somewhere before.
    But what does happen, so I'm led to believe, is a major gravitational upheaval. As most of us here probably realise, it's widely thought by scientists that our Oort cloud can be disturbed by the gravity of stars passing within a certain distance of us, even in a relatively orderly system like ours.
    In the chaotic aftermath of a 'galactic mingling', as I prefer to think of it, the frequency of 'close passes' is expected to increase significantly. In our case, that mightn't bother the Sun very much but it would surely create another era of heavy meteoritic bombardment for the planets.
    There won't be any life on Earth, of course, in 2 or 3 billion years but increased planetary bombardment throughout our galaxy and Andromeda might make life difficult or impossible in many other star systems - preventing its genesis in some cases or snuffing it out in others.

    I know there are people who recoil at the idea of humanity moving asteroids, comets and KBOs around to suit themselves in some technologically advanced future - playing celestial snooker! But, when you look at mother nature carelessly smashing whole galaxies into each other .. !!
    It's evidently an uncaring universe out there and planetary real estate isn't really sacred. That's why terraforming and celestial snooker don't bother me that much, I guess. Life is short and the life of a species is short; I think we need to grab our opportunities with both hands.
                                                 

Hmmm.
    I was aware that Earth's continental crust is thicker than the oceanic crust but I didn't realise the ratio is 7:1.
    The oceanic plates are disconcertingly thin!