New Mars Forums

You bet, Cindy.  "Wow" is right!   
    These are exciting times in both Cosmology and Physics. I've only just been reading about the possibility of gravity 'leaking' into higher dimensions in the recent edition of New Scientist magazine.
    Apparently, such 'leakage' would explain why gravity, of all the fundamental forces, is so extraordinarily weak. Of course, when you trip and fall and land with a thump on the ground, gravity doesn't seem weak at all; in fact, it seems all together too strong!  But, when you pick up a pin with a toy magnet, that little magnet is out-pulling Earth's 5,980,000,000,000,000,000,000 tonnes of mass.

    So, where did these higher dimensions come from and where are they? Why can't we see them and move around in them?
    Well, they were first mooted as part of string theory, which describes all matter and energy as consisting of infinitesimal strings rather than tiny particles. In this theory, the various characteristics of what we think of today as particles are explained by different vibrational frequencies of these tiny strings. But, if you understand the mathematics (I don't), one of the consequences of having tiny strings is that you get multiple higher dimensions into the bargain!
    The fact that we only notice three-dimensions-plus-time (sometimes called 4-space), is because the extra dimensions above and beyond these are curled up very tightly and are very small.

    It occurred to some very smart people that gravity's incredible weakness might arise from a loss of its strength via seepage into these dimensions.
    This, in turn, led to the not unreasonable idea that we should be able to use very sensitive measurements of gravity to: (a) test for the existence of curled-up extra dimensions by checking for measurable gravity leakage, and (b) get some idea of just how small these curled-up dimensions actually are.

    Anyhow, to cut a long story short, from the results of devilishly clever torsion balance experiments, it looks like the extra dimensions can be no bigger than 70 micrometres. And preliminary measurements from further experiments suggest no deviation from Newton's inverse-square-law for gravitation down to about 10 micrometres.
    Of course, none of this means anyone knows for sure that higher dimensions actually exist. They're simply placing constraints on the possible upper limits of the size of these little balls of curled-up higher dimensions .. that's all.

    Nevertheless, it's potentially ground-breaking research and it could have profound effects on our understanding of what makes the Universe tick.   

That 'Rainbows on Titan" article is very revealing about possible conditions on Titan. It's interesting to consider the different physical characteristics of a liquid methane lake, as compared to our more familiar watery ones. What a weirdly alien world Titan must be, while being oddly familiar at the same time!
    Sadly, I'll have been pushing up daisies for a very long time before humans set sail on a Titanian cryo-sea. 

[Ah well, maybe in my next life ..  :;):     ]

I didn't catch the story about spiders moving indoors in recent weeks, although we do get occasional things like that happening. Fortunately for me (don't get along with spiders, myself), we're living a few floors up in the middle of town and rarely see a spider of any description.

    I imagine the spiders you've heard about are our Redback Spiders - a close relative of your Black Widow and equally venomous, as I understand it.

    The Redback is a part of Australian folklore and is closely associated with the old-style outdoor toilet, which used to grace the backyards of homes and farms all over the country in the earlier days of primitive plumbing. There's nothing a Redback Spider likes more than to set up home in junk-piles sheds .. and yep .. outdoor toilets. So a visit to the toilet was often fraught with danger as people faced the risk of potentially exposing their delicate nether-regions to the Redback's poisonous fangs!
    In fact, the terrors of the outdoor toilet were immortalized in the darkly humorous 1972 song "The Redback on the Toilet Seat", by Slim Newton.

    As far as rainfall's concerned, we did have heavy rain during December/January but we've had an exceptionally dry February. Maybe this has taken the pressure off the Redbacks by allowing their habitats to dry out again (?).

    Here's one of the 'nasty wee beasties' - quite similar to the Black Widow, I believe, but with a red stripe on the back:-

Flashgordon:-

    Yes, I remember reading something to that effect. As far as I can tell, life will begin struggling at about 500 million years from now and, aside perhaps from a few forlorn colonies of subterranean thermophilic bacteria, will be extinct here in, at most, 1 billion years.   

    This, to me, is a profound tragedy. Life, in one form or another, has existed here for maybe 4 billion years and Earth is its only known refuge. To think that we're in the last 20% of our home planet's 'life' span is somehow unconscionable and puts me in mind of the poignant words of Dylan Thomas:-

"Do not go gentle into that good night,

Old age should burn and rave at close of day;

Rage, rage against the dying of the light."

    I just hope that whatever intelligent species exists on Earth in half a billion years will find some way to preserve Earth's legacy of life - so far the only life we know of for sure in a vast and lonely universe.  ???

Interesting thoughts, Flashgordon.   :up:
    I agree with you that there must be a limit to the ability of a living system to regulate its environment. Even an ecosystem as diverse and well-established as Earth's would surely have trouble maintaining itself if most of the atmosphere disappeared and average global temperatures dropped to -55 deg.C!

    Looking to the future, apparently Earth's tenure as an abode for life has 'only' about a billion years left to run. All of life's checks and balances will be powerless by then to combat the inexorable increase in solar energy output. Our home planet will overheat and terrestrial life will be destroyed - despite Gaia.   

    As you say, finding fossil evidence of macroscopic multi-cellular life on Mars may well require a permanent presence by scientists able to conduct unlimited field excursions.
    But serendipity could yet come to the rescue and Spirit or Opportunity could stumble across a perfectly preserved fossil at any moment. Stranger things have happened.
    If Mars Direct had been adopted vigorously by NASA as soon as it was devised by Dr. Zubrin, we would have had a couple of teams of scientists and their results back from Mars by now and a virtually continuous human presence there. It's certainly not impossible that, if there are any macroscopic Martian fossils to be found, we might conceivably have had samples of them in terrestrial laboratories today.

    I'm a bit of a Dr. Chris McKay fan and I believe he is open to the possibility that life could have developed earlier on Mars than it did on Earth. If so, multi-cellular life might have appeared quickly enough to catch the end of the hypothetical warm/wet conditions many scientists seem to think predominated there in the first 1 - 2 billion years.
    And as you suggest, the worsening climatic conditions may even have served to accelerate cellular cooperation, as is thought by some authorities to have happened here 590 million years ago, in the wake of a 'Snowball Earth' episode (?).
    Fascinating stuff!   :up: 

   [Keep watching those images from Spirit and Opportunity!!  You never know ...   :;):  ]

Rik:-

    Right ... that's it; now it's contempt of court as well!!
:angry:
    In addition to your incarceration with 'steenkin' hippies' in a Hab, you are sentenced to 30 lashes. Upon arrival in Mars orbit .. wait for it .. yes .. you will be tied to the Mars Express orbiter just prior to the deployment of its radar antenna!

    Designed for ESA by Dickbill, and originally based on plans he'd drawn up for a self-flagellation machine he was building in his basement, the Mars Express radar antenna will whip back and forth uncontrollably, delivering the lashes Rik so richly deserves.
                                                       [    ]
    This court is adjourned. Take the prisoner away!

Cindy:-

    Stunningly beautiful. 

Hi El Scorcho!
    I have serious reservations about your plan.

    There's protein in our food, and nitrogen in the protein, as you've quite rightly stated. And, if we eat the protein and don't utilize all of the constituents, we excrete nitrogen in the form of urea.
    So, there's no reason why we shouldn't be able to obtain nitrogen from urine.
    But where did the nitrogen in our food come from in the first place?

    Nitrogen in our food can only have come from the environment in which we grow that food. In a closed system, like domes on Mars, we can't produce excess nitrogen out of nowhere. If we get nitrogen from our urine and pump it into the dome's atmosphere, it will simply be recycled into our food so that we can eat it again.

    Unless I'm misunderstanding something here, your scheme seems to be rather like the magician's trick with the rabbit and the hat. Except you're producing enough rabbits to populate the whole of Mars - or, in this case, enough nitrogen to build a planetary atmosphere.

    I don't think it's going to work.

Thanks for the reply, Cindy.
    Yes, the situation re. organic compounds in the Martian regolith is puzzling, to say the least.  O.K., the GCMS did prove that there weren't large quantities of organic material in the topsoil on Mars, but to say .. :-

    " .. one of these experiments showed that the surface of Mars was entirely devoid of carbon compounds."

    .. seems to me to be a clear case of wilfully ignoring the GCMS's shortcomings. (But why?! )

      I would probably have accepted the report saying the amount of organic compounds was much lower than theory suggests should be there; that would make sense because the GCMS results did legitimately set an upper limit on the amount of organics. But subsequent tests have shown they're not sensitive enough at the lower end of the scale to justify the use of terms like "entirely devoid of carbon compounds".

    The fact that NASA is preparing to launch the Mars Science Laboratory in 2009, to seek out organics in the soil and analyze them, serves to underline the inescapable conclusion that even they themselves(!) don't believe the very GCMS results they've been touting as fact for 30 years!!
                                                   
    They can't have their cake and eat it too.
    But either nobody seems to notice the inconsistency or they're too nervous about funding to query it.  :hm:

    [By the way, thanks for humouring me as I carry on pounding the drum I've been beating for years now!  :rant:     ]

Grypd Quote:-
    "Actually the atmosphere we have has an oxygen atmosphere of 21% every percent over that is an increasing risk of fire. By the time we reach an atmosphere content of 30% a fire will be so hard to fight that it will be a nightmare."

    This is an interesting point and I've often wondered at just what percentage of oxygen spontaneous combustion becomes a problem.
    Apparently, oxygen levels in Earth's atmosphere have been much higher in the past than they are now, as described in this excerpt from a paper called "Atmospheric oxygen, giant paleozoic insects and the evolution of aerial locomotor performance", published on the 24th March 1998 :-

    It's interesting to consider that, while the oxygen level changes, the partial pressures of inert nitrogen and argon in the atmosphere remain constant.
    I did a little arithmetic and found that if the partial pressure of O2 reaches 35%, leaving the partial pressures of nitrogen and argon at about 780 and 9 millibars respectively, then Earth's sea-level pressure must have been roughly 1213 millibars, or about 200 millibars higher than today's figure. And the partial pressure of O2 would have been about 424 millibars - or double today's partial pressure!

    According to the paper I've quoted then, 424 millibars of O2 in a total atmosphere of 1213 millibars is regarded as the threshold for spontaneous combustion of the biosphere.
    But does spontaneous combustion depend solely on the percentage of O2, in this case 35%, or does the total pressure influence the threshold?
    In other words, can anyone tell me whether 35% O2 is still the threshold of spontaneous combustion in an N2/O2 atmosphere totalling only 500 millibars.

    My instinct is that the lower the total pressure of an N2/O2 atmosphere, the higher the O2 percentage-threshold of spontaneous combustion becomes. This means that you could have a Martian atmosphere of 40% O2 and 60% N2 (plus trace gases of course) without fear of spontaneous combustion because the total pressure is relatively low.
    Is this correct?  ???   

Hi Chat:-

    The question we're dealing with relates to the environment on Mars after full terraforming has been achieved. Full terraforming, in most people's minds, involves the creation of an atmosphere which allows humans to roam freely on the surface without the need for a pressure suit or respirator.
    Obviously, the ideal situation would be to create an atmosphere just like Earth's: 1013 millibars at sea-level, consisting of 78% N2, 21% O2, 0.9% Argon, 0.03% CO2, plus trace gases.

    However, there's no guarantee that the volatiles we would need to do this are available in sufficient quantity. As a result, it appears most people would be satisfied if we could create 'half an atmosphere', which is to say a surface pressure of about 500 millibars.

    To provide the same partial pressure of oxygen we enjoy here on Earth, i.e. roughly 210 millibars, it's clear from the figures that we need to enrich our 500 millibar atmosphere to 40% O2. So, we end up with air which is about 40% O2 and 60% N2, assuming we ever find that much nitrogen somewhere on Mars! Again, this brings us back to the fabled nitrate beds and the denitrifying bacteria Earthfirst has been talking to Clark about.

    But the point I've been trying to make is to compare this new 500 millibar O2/N2 atmosphere with the closest equivalent we have here on Earth, in an attempt to show that the environment on a fully terraformed Mars is, in fact, quite liveable for not only plants but humans. This is why I searched for inhabited regions of Earth at an altitude of 5600 metres, which gives us broadly the same ambient pressure as we'd have on our new Mars.
    And, sure enough, I discovered that 7000 people live at La Rinconada in Peru at an altitude of 5100 metres, where the pressure is about 530 millibars. Interestingly, the partial pressure of O2 at this altitude must be little more than 110 millibars, only half of the oxygen partial pressure our new Martians will experience at sea-level on Mars. And yet people have lived and reproduced under these adverse conditions in La Rinconada for 40 years - a testament to the adaptability of our species and perhaps a portent of how humans may change very quickly to adapt to life on Mars.

    When we've created the oxygen-rich atmosphere we're talking about, an ozone layer will form in the Martian stratosphere and reduce UV levels to no more than those experienced on Earth - almost certainly less, in fact, because of the O2 enrichment I mentioned, and because Mars is roughly 75 million kilometres further from the Sun (insolation being only 43% of that at Earth's distance).

    Gamma Rays and X-Rays are electromagnetic radiation, just like visible light. Such radiation is unaffected by magnetic fields. This means the lack of a global magnetic field on Mars makes no difference to the influx of this radiation - and in fact, our terraformed Martian surface will get no more of it than La Rinconada gets.

    Galactic Cosmic Rays are essentially atomic nuclei travelling at relativistic velocities. The lower energy Cosmic Rays are affected by the Sun's and Earth's magnetic fields and are largely stopped by a blanketing atmosphere. The heavier high-speed nuclei, while deflected by our magnetic field, still reach Earth's atmosphere. On the way through the atmosphere, many collide with atoms and produce a cascade of secondary particles, attenuating their penetrating power. But still, many reach the surface and this hasn't made life untenable on Earth.
    The Sun's magnetic field (and possibly Mars' scattered, 'fossil', crustal magnetic field) plus the 500 millibar atmosphere we propose to create, will stop all but the higher-energy Cosmic Rays. These will reach the surface of Mars in greater numbers than they do here but very probably not in show-stopping numbers.
    Experiments show that the number of Cosmic Rays penetrating Earth's atmosphere at the altitude of La Rinconada, is roughly double the number reaching sea-level. The number of high-energy Cosmic Rays reaching sea-level on a terraformed Mars is yet to be calculated, as far as I know, but I suspect it won't be dangerously higher than at La Rinconada.

    We should remember that roughly every 250,000 years Earth's magnetic field reduces to zero as it undergoes a polarity change. This has happened countless times throughout Earth's history and yet there's no evidence that this periodic 'lowering of the shields' has had any detrimental effect on terrestrial life.
    This is a telling indicator that Earth's atmosphere is much more important in protecting life on the surface from both Galactic Cosmic Rays and the Solar Wind particles than its magnetic field.

    I think it's inevitable that there will be a generally higher level of ionizing radiation on a terraformed Mars but I don't believe it will be anywhere near high enough to affect the viability of surface life. One consequence might be accelerated evolution through the agency of more frequent mutations - and this in itself will probably lead to the evolution of more radiation-hardened organisms, given time.
    I certainly don't agree with you, Chat, that plant life will be unable to survive on the surface of our new world; I think your analysis is way too pessimistic.
                                                       

Chat:-

    I don't think this is true.
    Earth's magnetic field is useful for diverting the impact of the solar wind and largely eliminating atmospheric loss due to 'sputtering'. But the vast majority of the radiation shielding we enjoy here on Earth is due to the sheer bulk of our atmosphere.
    A fully terraformed Mars is likely to have a 500 millibar atmosphere, which is equivalent to the pressure experienced by someone at an altitude of 5600m above sea-level here on Earth. However, the oxygen content will be 40% on Mars, whereas it's still only 20% at 5600m on Earth.

    Nevertheless, people have lived for up to 2 years at an altitude of 5950m on Earth [http://www.liebertonline.com/doi/abs/10 … ookieSet=1]see this site] and: "The highest permanently inhabited town in the world at the present time appears to be La Rinconada, a mining village of over 7000 people in southern Peru at an altitude of up to 5100 m, which has been in existence for over 40 yrs." (5100m is the equivalent of ~530 millibars.)
    The amount of space radiation received by the people of La Rinconada is not substantially less than the amount colonists will get on a fully terraformed Mars, despite the lack of a global magnetic field.
    And, if humans can live in a radiation environment like that, apparently indefinitely, then so can plants - especially plants deliberately bred for those conditions.