New Mars Forums

<discussing powering nano-robots>

Crystals form when you have a saturated solution in a liquid that is cooling or evaporating.  The gibbs free energy is lower for the atoms to come out of solution.  For some substances, they intermolecular forces favor a regular alignment of atoms or molecules, so a crystal forms.

However, the energy for putting the atoms into solution has already been placed into the system so the power requirements for forming the crystal have already been met.

In an oxygen poor flame, carbon will form bucky-tube like structures, but they are far from perfect.  They are sea shell like spirals, glommed onto flat graphite sheets, with several atom specks of diamond crystal structure.  All in all it makes a fairly good abrasive.  This is what soot is.  However, to form perfect buckytubes is far from easy, requiring precise conditions.  And you still need carbon atoms in a gas or plasma which is a very energy rich source.

Again, you are starting with a high energy state.  If you have lots of energy you can 'reverse entropy' for a while and create order.  But the energy was put in first.

Actually I have considered an idea like this but it won't work.  No machine can be built that will convert random heat into useful work with out a heat differential.  (2nd law of thermodynamics.)  See this URL: 

http://en.wikipedia.org/wiki/Laws_of_thermodynamics 

also

http://web.lemoyne.edu/~giunta/perrin.html

and

http://www.kilty.com/pmotion.htm

(You may want to look at "perpetual motion of the third kind" in the third link above, as your machine will use quantum effects to bring the warm reservoir down to absolute zero in a finite number of steps.)

Assuming the second law does not apply to your machine, I can see some problems:  first assume that the first atom that hits your piston pushes it in and you get some work.  OK what drives the piston back?  Do you have a working fluid on the other side of that piston?  Then your random molecular motion has to overcome the pressure of that working fluid.  If there is a vacuum on the other side of the piston then this problem does not apply, but you had to do work to put the vacuum there in the first place.

Or let us say that you have a bunch of paddles (like a paddle wheel) sticking out the side of your machine.  If you have a current going past it no problem, there is energy to be extracted there.  But if the fluid your paddle wheel is stagnant with only random thermal motion, then you have as many atoms bumping against the back of your paddles than the front.  If we make the paddles really small, then randomly we might get more hitting the front than the back.  But we now have to over come the energy needed to lift the ratchet, turn the whole paddle on its axle and to overcome the friction of the rod in the bucky tube (or spring or whatever) you are using to store the power. 

If you assume frictionless surfaces than perpetual motion is possible but you won't be able to extract useful work (in the physics sense of work) from the system.

Agreed.  But in Drexler's "Engines of Creation" he is talking about tiny machines that go inside cells.  He talks about machines that dismantle whole planets, get all the information in the planet, and then put the planet back together the way it was.  And so on.  The smaller the little robots get the more powerful they become and the harder the problems that I brought up are to solve.

<Talking about how chaotic / sticky the nano-tech environment is.>

Hydrogen tends to donate an electron to fill an outer electron shell.  Thus it makes the non-metals less sticky.  It won't help if you have a proton donor on your robot.  For that matter, even if hydrogen perfectly fits the bill, you still have to perfectly keep all surfaces clean until you can find a hydrogen atom to fit into this slot.  Not easy.  Furthermore the most common source of hydrogen is water.  If you grab one it its hydrogens you leave behind a hydroxyl ion which is powerfully reactive.  This powerful base will steal hydrogens from anywhere it can, and your machine is covered with hydrogen and near by...

Even a non-sticky atom in a molecule will sometimes react.  Chemical reactions are about equilibriums and while a surface may be pretty darn stable, sometimes you will get a reaction with it.  Such things destabilize your machine.  That is why cells spend so much molecular machinery to repairing themselves.

Note that biological systems also are troubled by the powerful electrostatic forces holding the atoms they need together.  They use an incredibly exotic array of enzymes and catalysts to help them.  Most fans of nano-tech seem to assume that they are assembling atoms like tinker toys in a vacuum.

I am not saying that nano-technology is impossible.  I am saying that it is DIFFICULT.  I am mostly interested in terraforming problems that could be attempted within the next 500 years.  Whenever someone says "Oh, we will just give Mars an oxygen atmosphere by building self-reproducing robots and having them take apart the soil.  Lots of oxygen in Martian dirt!", then I nod my head and think, "Yah.... right."

Too often nano-technology is used as a magical, mental crutch to allow the person discussing it to ignore tough problems.  My post was intended as a wake up call to those that think that it will be simple to solve any problem with nano-tech.  Usually the problem they are discussing (e.g. giving Mars an oxygen atmosphere) is easier to solve than their nano-tech solution would be.

However, nano-tech is potentially a solution to some problems.  If they suggest nano-tech (perhaps some sort of artificial enzyme to speed a chemical reaction) that discusses how to get around the problems I brought up then I would be DELIGHTED to hear from it.  It is just such creative solutions that will allow human colonization of Mars.

Let me give an example of a nanotech solution that will work (not using tiny robots tho, sadly...)

You can dissolve many metals in carbon monoxide (CO) making what is known as a carbonyl.  You can then fire a laser into the carbonyl tuned to the right frequency so that it will decompose the carbonyl and leave pure metal behind.  The CO gas floats to the top of the tank.

Using finely focused and controlled lasers solid metal devices can be built up one layer of atoms at a time.  Microscopic machines can be built of almost any shape.  Using mixtures of different carbonyls and different lasers you can even make a variety of alloys.

How does this idea for making microscopic machines deal with the problems I raise above?

POWER: External.  Not a problem.

CHAOTIC ENVIRONMENT: We prepare ahead a time a pure solution of say, iron carbonyl.  Given that the environment is one simple substance this problem is solved.

DIRTY ENVIRONMENT: We prepare a very clean environment (at considerable cost of effort) ahead of time.  Thus this is not a problem.

PROCESSING POWER: This is outside of our carbonyl lathe working surface so it is not an issue.  We can make it as large as we want.

This is an example of a nano-technology problem that is easy (altho I have not hear of anyone that has actually built a carbonyl lathe).  The machines that build nano-sized integrated circuits on a silicon wafer are likewise solved problems.

Note that the integrated circuit industry has spent billions of dollars and years of time to solve the very significant problems involved with chip foundries.

Warm regards, Rick

Hi Noosfractal, everyone.
  I am not sure if we have reached agreement or not from your post.  If the purpose is to move whole asteriods to Earth orbit than we should be looking at asteriods that perihelion or apihelion as close to Earth's orbital velocity as possible (either will do).  For this the L5 base you suggest would be ideal.  If we are talking about refining the materials at Mars or Venus and then shipping the pure metals to Earth the cost is largely immaterial since we will likely use light-sails or mag-sails and the only difference will be a few weeks time one way or another.

  I looked at your link. (It was a picture of the location of various bodies in the inner solar system for those who have not checked it out.)  The red dots are actually beginning to thin out a little by the time we get into Venus.  As a test, I counted 16 objects that's dots actually fell on Venus' orbit.  I counted that number of dots on Mars' orbit before I got 45 degrees around its orbit.  (And as I said before, the sample is not fair since the bodies near Venus come closer to Earth so it is easier for us to find them.)

  I am not sure what you are mean when you say "the Mars launch is still behind for the NVA".  Are you suggesting we should go after NVA from Mars?

Warm regards, Rick.

Hi everyone,
  I've been thinking more about these cities on Venus.

  My first question was would the sulfuric acid disolve carbon.  Yes (at least for any likely carbon composites).  But what if it was diamond?  I found at this URL:

http://www.nanomedicine.com/NMI/9.3.5.3.6.htm

So if you make your pressure walls some sort of carbon - carbon composite you will be in trouble.  But if you make it of diamond (or pure fullerene) it should be immune to the acid.  However if your fullerene is bonded together you need to worry about what glues it together.  Likewise the sulfuric acid will attack air lock seals.

The next question I had was how much boyancy would you get using N2 - O2 atm in a CO2 atmosphere.  Now the gram molecular mass of air is:

gmm N2 * 4/5 + gmm O2 * 1/5 = 28 * 4/5 + 32 * 1/5 = 28.8

The gram molecular mass of CO2 is:
CO2 = 12 * 1 + 16 * 2 = 44

Or our air is 63.6 % as dense as CO2. 

Looks promising so far.

But let us look at the Hindenburg.

It was filled with hydrogen gas with a gmm of 2, floating in air. 

Hydrogen is 6.94 % as dense as air.  In order to support the infrastructure, engines, passengers & luggage it had to be huge.

Now if you square the size of an object, its volume increases as a cube function.  So by making your cities bigger, (much bigger) the lower boyancy of air will keep them up.

Now we pretty much need a solid diamond outer surface which is VERY rigid.  You could have the air at a lower pressure than the outside.  If the air pressure inside is half, this would double the boyancy which makes air at a vacuum a much better lifting gas.

Hi noosfractal,
I find this hard to believe.  Venus has an escape velocity of:
10,400 m/s.  Even if we assume that this is only 90% at 50 km height that is: 9360 m/s.

Mars has an escape velocity of  5000 m/s.

Now maybe we have found an Earth crossing Near Earth Asteroid (NEA) which perihelion just touches the orbit of Venus.  You would have to match velocities which would likely be a burn of less than 500 m/s depending how circular its orbit is (the rounder the better).

Even so, you will need a delta vee of close to 11,000 m/s to get to any NEA close to Venus.

Are there any asteriods that get as close to Mars' orbit as some NEA get to Venus'?  I don't know.  They would be a lot harder to detect a Near Mars Asteriod (NMA) than to detect a NEA (which is then followed closer to Venus).  However, Mars is close to the asteriod belt and I would guess that there are a lot more NMA than NVA.

However, let us say that a there are no NMA for some reason.  The only ones are Medium Far Mars Asteriods (MFMA of course).

When you launch from Mars, you still have 4,800 m/s of delta vee to get to the MFMA and still beat the Venus launch.  I think that there likely plenty of small bodies near Mars that will beat your NVA.

Anyone see any flaws in this argument?

Do you have any particular asteroids you were thinking of.  If you give me their orbital parameters I can run this with real numbers.

As for putting cities underground in Venus, there is strong evidence that Venus is volcanically active.  So the temperature will increase as you go deeper.

Warm regards, Rick.

Hi all, Karov.
  Thanks Karov.  I had assumed that we would want the Martian lakes and oceans to be as much like Earth's as we could get.  I had never thought that we might prefer to have the water stay slightly acidic.  Very clever.

  The link below suggests that water with some sulfuric acid dissolved in it (this is called oleum) would stay liquid far below water's normal freezing temperature.  Oleum would be VERY acidic.

http://www.astronomy.com/asy/default.aspx?c=a&id=3782

  Unfortunately, Oleum is extreamly unhospitable to life.  Later in the article they talk about another region where clay minerals suggest the water was not that acidic and life could have lived in that environment.

  Mars just keeps getting stranger and stranger! 

  Warm regards, Rick.

"Moons & Planets 3rd Edition" by William K. Hartmann, Wadsworth Publishing Co, (c) 1993, 510 pages.

This book is out of print but I found a number of copies on Albris for under $10.00.  Well worth the price even counting shipping.

I have several text books on astronomy but this is the one I usually turn to when I need data on planetology.  Rather than starting at Mercury and working its way out, world by world, this book is based on comparative planetology.  It teaches some fundamentals (on geology, meteorology or whatever) then compares each planet to each other emphasizing that topic.

One of the biggest strengths of the book is how multi-disciplinary it is.  It covers physics and geology, chemistry and meteorology, biology & orbital mechanics, history and experimental science (by probes).  I was charmed to find a solid foundation on geology and minerals in an astronomy book.

It is a dense read.  There is a LOT of material in this book.  It is aimed at the university student, however most of the math is in sidebars set apart from the main text.  So people with a high school education, can enjoyably read the main text, ignoring the calculus and calculations for the most part.

The book has many photographs, tables and charts.  Also the author is an accomplished artist.  Several beautiful paintings of space subjects have been done by the Mr Hartmann.  These include a striking painting on the front cover.  (This shows a small meteor impacting Rhea, with Saturn in the background.)

The author shows you the alchemical symbols for the planets (including new ones for more recently discovered bodies).  These are used in graphs extensively, so you can see where the various planets sit, with out having to cover up the diagram with the planet names.  This is typical of the  clever graphic design thru-out the book which packs a lot of information into a small space.  (In an easy to read way.)

The major disadvantage of the book is that it was published in 1993.   I would love to see this book get updated to include the new discoveries we have made.

>>> EDIT: there IS a new edition that has come out in 2005.  It sells for a bit over $100 bucks.  Good new indeed! <<<

However, much of its data is still accurate and it is a literate, well crafted work.  I recommend it as an intermediate to advanced text for people interested in planetology.

Warm regards, Rick.

Hi nickname,
  No problem.  Yes it is easy to come across the wrong way in email and on forums.  I should try to use more smilies...   

  I doubt that we will find solid CO2 under ground on Mars' equator.  The thing is that the temperature goes up because Mars has been volcanically active in the last 250 million years in many areas on the planet.  This means that there is a lot of ground heat, so temperatures will go up as you go deeper.

  However I expect that there are CO2 deposits underground at the equator: both dissolved in water & in ice as clathrates.  Liquid CO2, held at pressure under a H2O cap, is possible tho more likely in regions nearer the poles.

  Warm regards, Rick.

Hi nickname,
  It is far too warm for solid CO2 to form at the Martian equator.  It can only form at the poles in winter (when the sun never rises for several Earth months at a time). 

  I was going to recommend a good primer in astronomy and planetology but I don't know of any.  (I have a dozen books but they are all advanced.)  Does anyone know of a good basic astronomy book that gives a fair bit of information on Mars?

  Warm regards, Rick.

Hi nickname,
  From my readings I think that the situation is that some time ago (say 1,000,000 years ago) Mars was such that ice was stable at 40 degrees of latitude.  Now things have changed so that the ice is subliming / melting at 40 degrees.  Some of it seeps deeper into the soil and refreezes.  Some evaporates and is deposted as frost all over the place.  If it does so north of (say) 43 degrees it is stable for a long time.  If it freezes at midnight at the equator, then around 2:00 pm it is likely to be in the air again looking for some place else to freeze out.
 
  There is a fair bit of evidence that ice is melting in many places on Mars.

  Regards, Rick.

Hi everyone, nickname.

It is almost certain that Mars has lost water because it has been broken up by ultra violet light.  However this takes millions to billions of years, and buried water is pretty much immune.

The iron in the planet's crust is red (likely) because of the oxygen released from water this way (unless there were plants on Mars once).  The oxygen oxidized the local minerals making giving iron the red 'rust' colored valence state.

However, the water loss is slow and Mars gets more volitiles from carbonaceous chondrite meteors, comets and from volcanic eruptions.  Is the water loss from H2O dissociation slow enough?  The proof is in the pudding.  We have detected a lot of hydrogen in the top meter of the soil at the high latitudes (40 degrees and above) so obviously the dissociation is slow enough that plenty of water can remain despite tilling of the subsoil by meteors.

Water in the air will frost out, be covered by dust, be absorbed into salts and other minerals that can be hydrated, etc.  Also every water molicule that breaks up does not mean the hydrogen is lost at once.  A hydrogen ion is very reactive, there is a good chance that something else will grab the naked proton before it gets a chance to be lost to space.

Lastly, small amounts of hydrogen get absorbed by the atmosphere.  Mars has a tiny amount of free O2 in its air.
(About 0.001 Pa partial pressure if I remember right.)  Some of the solar wind might react with this O2 (the exosphere is hot enough) and this would form more water. 

(Does anyone have any idea how much the rate of hydrogen - solar - wind - capture would speed up if there was more O2 in the Martian atmosphere?  Is this effect at all significant?  Most discussions ignore it but I see no reason why it could not happen.)

I suspect (this is musing on my part) that water  & ice crystals are more immune to break up by UV.  If the UV dissassociates a hydrogen from H2O in ice, the proton is trapped by the ice crystal.  The ice will form H3O+ and OH- (hydronium and hydroxide ions) which remain in the crystal and will eventually neutralize each other.  Ditto for water.

Earth has lost quadrillions of tonnes of water to UV light.  People estimate that Earth has lost about a meter of water from its oceans per 1 billions years to this cause.  (The slow rate of this process on Earth is largely because of the 'cold trap' that keeps most of the H2O away from the most powerful UV radiation.)

Lastly remember that Mars gets about 1/2 the UV light that Earth does.  The process will happen slower on Mars.

Warm regards, Rick.

Hi Josh, everyone.
  Very cool link Josh.  You can also make a 3D fabber using carbon monoxide reacting with many metals to make carbonyls.  (A fluid with the metal surrounded by CO.)  Using lasers the carbonyl can be decomposed into almost any 3D shape allowing metal parts to be made of various alloys. 

  With fabbers making plastic parts and a carbonyl lathe creating metal parts, this will jump start industrial development on Mars.

  Many thanks!

  Warm regards, Rick.

Hi Joseph.
LOL ! 

That is a new one to me.

Warm regards, Rick.

Hi nickname, C M Edwards, everyone.
Your idea got me curious.  Is there enough mass on Phobos to do the job?  Let us say that we grind Phobos completely into dark dust.  We likely need a thickness of at least a millimeter of dust to significantly darken Mars' surface.  What is the mass of a mm of dust?

Let us see, if we assume that it masses the same as carbon, then one gram of carbon masses (graphite) ranges from 1.9 to 2.3 g/cm3.  (I'll pick the lower value.)  1mm x 1cm x1cm is 1/10 of the volume of cubic cm, so this means that the mass will be 0.19 g/cm^2 (to cover a square cm of Mars).  There are 10,000 square centimeters in a square meter so this becomes 1900 g or 1.9 kg of dust to cover a sqare meter 1 mm deep.

Is the assumption that Phobos has the same mass as carbon a good guess?  Phobos is thought to be a Carbonaceous Chondrite which are made up of: "carbon in the form of poorly crystallized graphite, fine-grained clay minerals, organic polymers, magnetite and iron sulfide."  (They also have other volitiles that have burned off when they fall to Earth.)  Their density is about 2.2 g/cm^3.  (Other Chondrite meteors have densites of around 3.6 g/cm^3.)

Compare this to Phobos which has a mean density of ~1.9 g/cm^3 (which makes sense as its volitiles have not burnt off as they fall thru the Earth's atmosphere.)  However if drop powdered Phobos on Mars those volitiles will be baked off in the atmosphere and on impact.  So rather than using pure carbon, it would likely be safer to use the 2.2 g/cm^3 density for Carbonaceous Chondrite meteors. 

This means that we need 2.2 kg per square meter of Mars.

I will further assume that Mars is a perfect sphere.  This gives it an area of: 

surface area = 4 PI r^2 = 4 * 3.1415 * 3,398,000^2 = 1.45 E 14 square meters.

So we will need 3.19 E 14 kg of dust to cover Mars this way.

Phobos has a mass of 9.6 E 15 kg however, the volitiles will be lost which (looking at the ratios of Phobos to Carbonaceous Chondrites) would be about 15% loss. Even so, there is enough mass in Phobos to cover Mars to a depth of about a 5 cm.  Phobos has a radius of (very roughly) 140 km.  Dividing this radius by 50 means that we would need the top 2.8 km of Phobos to cover Mars to 1 mm depth. 

*********************************************************************
EDIT:  Joseph_Dunphy noticed an error above.  Phobos is 27 by 22 by 18 kilometers not 140 km I use above.  (I mis-read the table.)  He sent me a correction off line so as to not embarrass me.  What a nice guy!!!  Averaging this is very roughly a radius of 22 & 1/3 km.  Dividing THIS number by 50 means that we will need about 445 meters of soil.

Many thanks Joseph for pointing out my mistake.
**********************************************************************

So we will need a lot more than the top few meters of Phobos to do the job, but in principle it is totally possible.

Now Mars' regular dust will blow about and this new dust will get concentrated in areas or covered up in others.  So we might well want to us a lot more than just 1 mm as a safety margin.

Mars has an albedo of 0.15 and Phobos has an albedo of 0.05.  (The closer to zero the albedo is the closer to totally black it is.)  I'm out of time so in another post I will calculate the black body temperature of Mars if we turn it as black as Phobos. 

The size of Mars & Phobos as well as info on Carbonaceous Chondrites was from "Moons & Planets 3rd Edition" by W. Hartmann.

Warm regards, Rick.