Could we, in the near future, artificially create a stable ozone layer around Mars?

  1. Near future no in the medium to far range future (Say 500 years)sure. We could setup manufacturing facilities on Mars and allow them to spew Carbon dioxide as well as Ozone and Oxygen into the atmosphere. Once there Oxygen would go through the Ozone-oxygen cycle eventually turning into Ozone while carbon would just help thicken the atmosphere increasing Atmospheric pressure on the surface. The increase in Carbon dioxide could over time allow for some species of plants to survive on the surface of Mars. This in turn would jumpstart the Carbon-Oxygen cycle which will reinforce the Ozone-Oxygen cycle.

    Edit Note: The Ozone layer would require continuous engineering to maintain due to the reduced gravity of Mars that allows for more of the atmosphere to escape into space.

  2. If you are interested, I highly recommend the speculative [Mars trilogy by K.S. Robinson] (http://amzn.com/0553560735). More than just about the colonization and terraforming, the books go deep into the geopolitical ramifications of having a new colony.

    Plus, Robinson is a kickass author. My second favorite after Asimov.

    In Red Mars, they use a combination of techniques to enrich the atmosphere. The most effective was to aerobrake a series of comets through the atmosphere, melting the ice and adding gases.

  3. There are a few serious issues that stand in the way of humans being able to colonize Mars.

    1. No atmosphere. You’ll need the right balance of gasses in very large quantities. Also getting some water onto the planet is a good idea.

    2. No magnetic field to keep the atmosphere to the planet. Mars supposedly used to have an atmosphere (there is evidence of this, but we don’t know for sure yet) but without a magnetic field it was all blown away by solar wind. In addition, humans will need sheilding from cosmic rays and solar radiation.

    3. It is cold. Real cold. You would need a power source to keep it warm enough for life as we know it.

    4. No nutrients in the soil. No plant life will grow

    5. No water (see point 1)

    6. Really fine sand on the surface that makes running machinery difficult.

    As far as advances towards addressing those problems, it looks like the only options we have at this stage is to ship over the things we need like air, water, heat sources and electromagnetic sheilding. Certain molds have been found to live in very harsh environments on earth, like the Arctic or the bottom of the ocean, so those may be useful in establishing an ecosystem on Mars. Until we have the technology to create a massive magnetic field around the planet, our best hope is to create something like Bio Dome.

  4. No, and it has very, very little to do with magnetic fields (Venus has no magnetic field to speak of and has an atmosphere twice as dense as ours).

    Mars gravity is only 38% that of Earths which means that if we could snap our fingers and give it the same density, temperature, and chemical makeup atmosphere that Earth has, most of it would just boil off into space Very quickly. We’re talking whole percentage points a day the first few days. It would only take a few hundreds to thousands of years to loose so much it would not be dense enough to support human life. After a million or 10 million it would be so thin that water would be rare (because it would boil immediately, even at very low temperature) Eventually, it would reduce to what it has now, about 1% of Earth’s atmosphere density (but that would take a few billion years).

    If you’re thinking we can just keep making more atmosphere, no we can’t; it’s a huge volume of matter. If we converted Mars rock into atmosphere it would need to be at a rate comparable to a major coal mining operation. So doable, if we could magically convert rocks into air and wanted to waste all that effort doing it.

    Of course, the easy thing to do is to dig a VERY deep hole so all the atmosphere falls in (like the reverse of climbing a mountain, the atmosphere would get a lot denser at the bottom of the hole). That’s the only real strategy for maintaining outside conditions that could support non-microscopic life.

    EDIT: More realistic timeline
    EDIT2: Acknowledged that lack of magnetic field does have an effect, however minuscule compared to thermal loss it would be.
    EDIT3: Current loss rate of Martian atmosphere is about 100 tons per day. It would increase exponentially based on the distance of the upper atmosphere from the planet and the temperature of the atmosphere. If you put our atmosphere on Mars as it is right now, the loss rate would be in the billions or even trillions of tons per day, but quickly taper off as the density and temperature dropped.

  5. I’m not sure about the ability to create an ozone, but if we could it would still get blown away by the Sun’s solar wind like it’s original atmosphere. Mars has a weak magnetic field, because the core is too cold to create a strong enough one that would protect the outer layers of the atmosphere from being blown off by the sun or protect us on the surface from harmful radiation. Maybe at the point that it would be practical to try to colonize the planet we may have a way to create a new magnetic field or substitute. I doubt we could even jump start it’s core, though if we did, it would cause massive volcanic and earthquake activity, though that’s pretty much a guess on my part.

  6. I say we start smashing icy bodies into it until it is way bigger with a hot rotating core and lots of water. Sure it would take thousands of years for it to stabilize enough for proper colonization but the improvements would be so worth it. It would really only cost a few trillion dollars. Just takes a long time.

    Edit: This isn’t layman speculation here. Many qualified people have proposed doing exactly that. It just so happens to be my favorite plan because it has the most foresight and permanence and it is even remarkably cheap and easy compared to other methods.

  7. Mars has several problems that contribute to it’s environment, a complete lack of a magnetic field due to a solidified or non moving core offers no protection to atmospheric gasses to the solar wind. Because of this, Mars has almost no atmosphere, the density is about 1% of earths and composed of all carbon dioxide. We would have to add massive amounts of oxygen, nitrogen, carbon dioxide and other greenhouse gasses to change the climate there. Due to no magnetic field, it would be slowly lost to solar wind, so we would have to constantly replenish it.

  8. You know I’ve thought about this and I don’t think it would be that hard. In the future I would think that force field use will be quite prevalent and so, if you used a force field as we use piping nowadays we could “pipe” gases from the gas giants in the solar system to mars. Now, the question I don’t know the answer to that I just thought of is what about an Ionosphere and the magnetic field of mars? Isn’t the ionosphere what protects earth from all the dangerous radiation emitted by the sun? Well, we might have to fix that too? Short answer, yes, most likely.

Both Stone and Sam Adams announced beer with helium for April Fools. But is it actually possible, or desirable?

    1. Helium is one of the least soluble gases. For comparison, you can get about 2.5g of CO2 into 1 kg of water at 10C. Under the same conditions, you’ll get about 0.0016g of He.
    2. No, helium is non-reactive. With everything. It is not toxic, nor is it used in any biological process (that I know of) in the human body.
    3. Yes, but as soon as you break that seal, the Helium is going to come out of solution. Quickly. And messily.

    For those interested, here’s the Bunsen coefficients of Helium and Neon, taken from Weiss 1971.

  1. The obvious gas to mix into beer instead of CO2 is N2O, nitrous oxide, which would give you a drink you might call a brew ha-ha. Wiki notes that you can dissolve 1.5 g N2O into 1 liter of water, and that it is soluble in alcohol. I found one reference of someone who tried it. He said that drinking the beer didn’t give him any nitrous buzz.

  2. CO2 dissolves in water. Nitrogen largely does not. Typically a “nitrogenated” beer such as guinness is pressurized with a 25%CO2 75%N2 gas blend, called beer gas. The CO2 will dissolve and the N2 is used to force the beer out of a special tap called a restrictor tap. The tap forces the beer through several pin holes, causing the CO2 to come out of solution and form small, very stable bubbles.

    WRT He, a quick google search indicated that He is even less soluble in water than N2 is, so you could use He as a stand in replacement for N2 in a nitrogenated beer with no effect on flavor. The only difference would be on your wallet.

  3. Tl;dr. Go have a Guinness.

    At moderate temperatures and pressures, such as those in your delicious beverages, Henry’s Law reasonably describes how much gas dissolves in a solution (at constant T). The relationship is directly related to the partial pressure of the species of the vapor headspace:

    p=k*c

    where p is the partial pressure, k is the Henry’s Law Constant and c is the concentration of the gas in the solution. Assuming the vapor space pressure is constant between normal carbonated beer and your Helium beer, the amount of He that will dissolve in solution (k = 3.7E-4) is nearly 100 times less than the amount of CO2 (k=3.4E-2) that has dissolved. You would expect there to be much less He to be dissolved, therefore I’d expect a smaller volume of bubbles to be released when compared to CO2.

    If you increased the He pressure in the headspace, more He would dissolve. However, it would be a packaging nightmare to get a high enough equilibrium pressure to see any appreciable increase in concentration.

    I don’t know enough about the surface tension between He and water to tell you how big you would expect the bubbles. Maybe I’ll get back to it after a little research…

    I’ve never had this helium beer, but I’d imagine it would be close to Guinness, which is packaged with a low CO2/high N2 mix. N2 will dissolve just about as well (k=6E-4) as He, and is pretty inert as well. You’ll probably get close to the same feel and probably the same type as head as a Guinness.

    Not a packaging engineer for a brewery so I don’t know what technology they use for seals, but I do know that helium-tight testing is the gold standard for determining a good seal on housings–so they better be good. I’d be more certain of cans holding their seal than any cap, compression, or screw lid. Plastic bottles–forget about it. Even CO2 diffuses across the thin plastic wall. Helium would make this beer go flatter faster.

  4. Just sealing helium in a container is difficult. Helium will leak through solid glass for example. Helium will zip right through the bottle cap to glass seal joint. Source: I have patents on how to seal the stuff in containers.

  5. Complete aside, but it’s worth noting that the CO2 providing carbonation in beer is a natural byproduct of the beer-making process (unlike in say soda where CO2 is added as a separate step).

    During fermentation, you add yeast to the wort, and the yeast converts the starch and sugar of the wort and produces alcohol and CO2. Granted, I’m sure that some beer manufacturers also add in extra carbonation or nitrogen in some situations.

  6. Adding helium to a liquid displaces all the other dissolved gasses (including oxygen and carbon dioxide). I used to do this with our HPLC mobile phases. It’s called sparging and it would ruin the beer.

  7. There are many good replies here so I will make it brief. Nitrogen is added to beer now precisely because it is not soluble. When it gets trapped inside a bubble on the head of the beer it is less likely to diffuse out, therefore long lasting head on a well poured Guinness. I expect helium would act similarly, except it might float away.

When we tag animals so they can be tracked and counted, do the tags affect the way their peers relate to them? Does it affect their mating chances?

  1. It really depends on the species. Those species that depend more heavily on smaller color features are more likely to be affected by bands. It’s an important consideration in the design of bird tracking studies! Here’s an interesting study on zebra finches that found a preference in female individuals for males with red beaks or red identification tags:
    https://www.google.com/url?sa=t&source=web&rct=j&ei=usM2U7axGXesATtz4LICQ&url=http://www.researchgate.net/publication/51315807Ultravioletvisionandband-colourpreferencesinfemalezebrafinchesTaeniopygiaguttata/file/d912f512de0e932317.pdf&cd=9&ved=0CEEQFjAI&usg=AFQjCNHi1GSMYhshNsrrivSGYnit5fpOKQ&sig2=S10L3SAHhr5iqXE1TCChjQ

  2. Another consideration is how the tag or band might affect their physical movement. For example, with microbats we have to be very careful with radio tags to ensure they don’t substantially impede flight– even if the transmitter only weighs half a gram.

  3. I worked with a group tagging monkeys, and we had to put quite a lot of instrumentation on the poor guys. They were immediately ostracized from the group because of their unfashionable ‘jackets’, but we would capture and release then back into the group no problem in a few days.

  4. Yes! You are absolutely right! Even small tags have shown to affect mortality and breeding rates n penguins in this landmark 2011 study: http://www.nature.com/news/2011/110112/full/news.2011.15.html

  5. A general rule of thumb is to use a tag or collar no heavier than 2-5% of the individuals body weight. Everyone tagging an animal has hopefully considered all possible costs, including a litany of behavioral costs (foraging, interacting with the same species, raising young, etc). interestingly, lots of reptilian or amphibian tags are actually implanted into body cavities (hellbenders, for example: https://ag.purdue.edu/fnr/discover/HerpetologyLab/Documents/StoufferSurgicalImplantation.pdf) or even sewn on to the back of the animal with dissolving sutures (http://www.herpconbio.org/volume1/issue1/Bull2006.pdf). Wildlife biologists often have to resort to these seemingly invasive methods due to the body shape and skin type of reptiles/amphibians. These methods are usually used only when everything else has been ruled out as more damaging or a greater hinderance.

  6. This is something discussed by statisticians as well as biologists when considering what are called capture-recapture methods. You capture some amount of animals, tag them, release them back into their habitat, and then later recapture some new amount and this will give you a good amount of information with which you can make an estimate on how many total animals there are in this habitat.

    Now, what you are asking if whether the tags we place on animals have any effect on their “lifestyle”. Well the answer is: it depends! It definitely can have an effect on the things you mentioned but since we are aware of this we, as statisticians or biologists or what have you, try to minimize the impact of the tags on the animal. It won’t help us estimate the total population if any of the tags go missing unexpectedly (ie: a colorful tag making some animal very visible to predators is bad).

    TL;DR: Yes the tags do affect them but we try to make the tags such that the effect will be minimized.

  7. Not directly related to color, but it was found that certain penguin tags could increase drag when the birds where swimming and hurt their survival chances, source

  8. What about the selective process of capturing animals to tag? A priori I would wager that in general a researcher would be catching less fit individuals. For example, if a researcher is trapping birds, he / she is more likely to trap a sick, unfit bird than a fit, fast, intelligent (and sexually selected) bird.

  9. I was watching a show the other day about tagging lions. They chose to tag & also give a birth control to the lioness, since her male companion would stay with her. What was interesting is that the reason they don’t do the male (for birth control reasons) is that he will lose his mane, therefore losing his stance in the pack.

How close together are the stars near the center of our galaxy?

  1. Short answer, yes! (with some assumptions)

    According to these lecture slides, the stellar density near the Galactic center is ~100 stars per cubic parsec (compared to ~1 star per cubic parsec in the stellar neighborhood). This corresponds (assuming I did my math right) to an average distance between stars of 0.13 parsecs (0.42 lightyears). If a star like the Sun were that far away, it would have an apparent magnitude (in V-band) of -4.6 mag. Wikipedia lists -4.0 as the faintest magnitude at which one can see things in the daytime sky with the naked eye. Since -4.6 is brighter than -4.0 (because smaller magnitude means brighter object) you could see a star like the Sun at 0.13 parsecs away (although, probably only if you have good eyesight). If you have stars in the sky that are brighter than the Sun or closer to you than the average distance between stars, then you’ll have a better chance of seeing them.

  2. http://i.imgur.com/RibFV9P.gif

    http://www.astro.ucla.edu/~ghezgroup/gc/pictures/orbitsMovie.shtml

    > A 2.2 micron animation of the stellar orbits in the central 0.5 arcsec. Images taken from the years 1995 through 2013 are used to track specific stars orbiting the proposed black hole at the center of the Galaxy. These orbits, and a simple application of Kepler’s Laws, provide the best evidence yet for a supermassive black hole, which has a mass of 4 million times the mass of the Sun. Especially important is the star S0-2 as it has has been observed for more than one full orbital period, which is only 16.17 years.

  3. Because stars are so closely packed together near the galactic center, the night sky for inhabitants there would be spectacular. Near the galactic center, the average distance between neighboring stars would be only 1000 AU (about a light-week). If the Sun were located within a parsec (=3,2 light year) of the galactic center, there would be a million stars in our sky with apparent brightness greater than Sirius. The total starlight in the night sky would be about 200 times greater than the light of the full moon; you could easily read the newspaper at midnight, relying on starlight alone.

    Source: http://www.astronomy.ohio-state.edu/~ryden/ast162_7/notes31.html

  4. Within a parsec of the galactic center, the estimated number density of stars is about 10 million stars per cubic parsec. The number density of stars here in the Sun’s neighborhood is a only 0.2 star per cubic parsec.

    The nearest star to the sun is about 4 light years away. In the galactic center, the average distance between neighboring stars would be only 1000 AU (about a light-week). Not only would the starlight to be bright enough to read by at night, many of those stars would be visible during the day. However, I doubt anyone is looking up into those spectacular skies. Most of the stars are young and hot and will explode as a supernova within a few million years. Between the supernova and any outbursts from the nearby supermassive black hole at the galaxy’s center, most of the planets in the region have been sterilized from the radiation.

    http://www.astronomy.ohio-state.edu/~ryden/ast162_7/notes31.html

    http://www.space.com/414-death-stars-sterilizing-galactic-center.html

  5. Hopefully, this is a acceptable reply. Try downloading Space Engine.
    http://en.spaceengine.org/

    Its a universe simulator. It has procedural generation of every star in every galaxy so you can visit all of them. (Yes, every star in every galaxy). All types of planets are simulated so you can find one with water and atmosphere go down to the surface.

    For what you ask, I would fly to the center of the galaxy and search for a star with a planet system. Then I’d land on the planet on the day side and see what the sky looked like.

    http://en.spaceengine.org/_ph/8/114589036.jpg

    quick tutorial:

    mouse wheel for speed and forward and back arrows to travel

    click to lock, “g” to go to the selectged object

    “F2” to identify planets around a star

  6. The center of this image is the site of Sagittarius A*, a point containing an extremely dense mass widely thought to be the supermassive black hole at the center of the milky way, with stars in very tight orbits. The orbits of a few objects in our solat system is provided for scale.

  7. A quick wiki search gives you the following:

    > A typical mass density for a globular cluster is 70 MSun pc−3, which is 500 times the mass density near the Sun.

    Apparent magnitude, or how bright we see objects here on earth, is on a logarithmic scale. log(500)= +/- 2.7

    > Brightest star (except for the Sun) at visible wavelengths: Sirius at -1.47

    > Faintest objects observable during the day with naked eye when Sun is high at –4.00

    Note that the lower the value, the higher the brightness. E.g. the sun has -26.74. Now I feel like I’m cheating a little bit by equating the mass density to apparent magnitude, but I suspect it is at least a good indicator.

    -1.47 -2.7 = -4.17 which is just bright enough to see when the sun is high.

    Therefore my answer to this question would be yes, but barely.

    *Edit: That said, if you are anywhere near a star like R136a1, you are very likely to see them during the day. It has a luminosity of 8.700.000 times that of the sun.

  8. Apparently, stars are packed very close together. 10 million stars per cubic parsec; around our neck of the galaxy, it’s about 0.2 stars per cubic parsec. Source.

    A cubic parsec is roughly 3 x 10^49 cubic meters. If we assume the stars are evenly distributed, that’s 3 x 10^42 m^3 for each star. Which would mean that the stars are about 1.5 x 10^14 meters apart from one another. The distance from the earth to the sun is 1.5 x 10^11 meters, so these stars are separated by about 1000 AU. So I’d hypothesize that you probably wouldn’t be able to see other stars during the day. However, the night sky would probably be really really cool looking. You’d have 10 million stars within half a parsec of you (1.6 ly). From earth, the closest star is Proxima Centauri, which is 4.3 ly away.

If photons travel at the speed of light, and time is dilated as you approach this speed, does this mean that all photons are precisely zero seconds old by their own reckoning?

  1. An assumption of special relativity is that light travels at c in every frame.
    Going by that assumption, there’s no such thing as light’s rest frame (point of view) – because if there was, light would not be travelling at c in that frame. In a way, I suppose you can take this as confirmation that a beam of light’s frame exists for zero time and spans zero distance, as it were.

    If photons do not in fact move at c and have a tiny, tiny mass (which is not ruled out but would be surprising), then indeed they would not experience much time at all during travel.

    > For example, in modifications of the double-slit experiment the state of the photon can appear to be changed in the past.

    I’ll leave this bit to other people (I still haven’t heard a good explanation of those experiments), but I suspect you’re just gonna get a lot of “that’s not actually what happens”.

    >However, according the photon, it’s departure, detection, and arrival may happen simultaneously, and therefore no “time travel” is actually occurring.

    This is a given: time in something’s frame always, always ticks forward, even inside closed time loops in general relativity. So that’s unrelated to time travel.

    >Does this have implications in quantum entanglement when information seems to have traveled faster than the speed of light?

    If you are careful about what you mean when you say information, no FTL happens. That “seems” is a trap, a pitfall.
    Relativity isn’t necessary to talk about quantum entanglement, nor does it dramatically modify it.
    For what it’s worth, entanglement makes perfect, intuitive sense in the many worlds interpretation…

  2. This video on the Relativity Paradox and Muons by Sixty Symbols[8:35] really helped me visualize the problems in imagining these things.
    It illustrates the compression and dilation over the professor talking. After reading the comments here, I think it will be a good supplement.

  3. >For example, in modifications of the double-slit experiment the state of the photon can appear to be changed in the past.

    What you’re referring to here, is the Delayed Choice Eraser. It goes like this:

    Particles which go through a diffraction grating will be detected on the other side as a single particle which followed a single path. (This is what is seen when attempting to catch out the interference patterns of electrons.)

    Waves which go through a diffraction grating, will travel through all possible paths at once, resulting in an interference pattern on the other side, with no way to tell which part of the detected wave followed which path.

    The idea is that if you change your parameters when the light is between your detector and the grating, then you can affect what form the light is detected in. If you change it’s form, then surely you changed the way it interacted with the grating, thus effectively changing the past.

    However. that’s not really how light works. Rather than “choosing” to be either a wave or a particle and then sticking with it, the light exists as a constant superposition of the two. And which one you detect can be affected even after it has been diffracted, resulting in no apparent reversal of causality.

    Note: Everything, every wave and particle in the whole universe exists in this manner. And the only reason we even use those terms any more is that our puny human brains haven’t evolved to understand complex wave functions.

Does Gravity travel at different speeds in different mediums?

  1. No, it always propagates at the same speed. If its path was warped by another gravitational field, it might appear to travel slower because it’s taking a longer route.

    edit: see here for a very small effect due to absorption of gravitational waves in different media.

  2. Sort of off topic. If gravity can be slowed going through a medium, can it ever be 1/2 phase off and cancel out the gravity in an area in a similar way to active acoustic noise cancellation? What would be the wavelength of a gravity wave? Would it depend upon the medium?

  3. Just a Question: do Forces move with the speed of light?
    I thought they were instant. So that there is no time needed for any Force to work? Or do I missunderstand that totally?
    And to my knowledge gravity is one Force.
    The proper question if my assumption is true would be:
    do gravitational waves do travel at different speeds in different mediums?

  4. Gravity travels at the universal constant which is the same speed that light travels at regardless of the medium. This is the same as light by the way. It travels at the same speed but it may appear to slow down in mediums such as water because of refraction but in reality it’s still traveling at the same speed it’s just harder to move in a straight line when you’re bouncing off things.

  5. The speed of light is the maximum speed, the speed of all information and massless things (including gravity) , it is the universal constant and not “just the speed of light”. Information may take some minor detours in denser mediums but it never slows down. space and time are relative and bendable while the universal constant is the same, regardless of your point of view and reference point.

    The speed of light is THE universal constant and all information propagates at that speed. We are just to small to notice it as much, but it takes some dozens of minutes between earth and mars and 1,4 seconds to earths moon. If we would be planet-sized we would notice the universal constant and bending of space time more easily. You could move your extremely long arm and it would take a few seconds for any noticeable effect.

    or you can just simulate a world where the speed of light is much slower:

    some high rated answers here are just wrong, it is sad.

  6. Light doesn’t travel at different speeds. The photons get interacted with by the matter of the medium, the main example of this is photons getting adsorbed by the atoms then re-emitted a shot time after. This appears to slow down the light when in fact, photons generally travel at c.

How did comets form,?

  1. Until somebody can give you a more thorough answer:

    Comets, like everything else form by a bunch of dust gradually getting clumped together by their gravity.

    What distinguishes comets is their composition.
    Water, dust, and ice make up comets because they can only form a certain distance from a sun, star or hot celestial body, whereas rocks can clump up together and stay intact in much hotter areas.

    Source: memory from intro to astronomy

  2. Here’s an article that may shed some light on the process of water formation in space:

    http://arxiv.org/PS_cache/arxiv/pdf/0805/0805.0055v1.pdf

    In short, it appears it’s possible for water to form from hydrogen interacting with solid oxygen at very low temperatures.

  3. /u/IBrokeMyCloset, this is why you should watch Cosmos (Fox, 9PM, Sundays), last night’s episode was all about comets.

    Like people here are saying, it’s basically a combination of nature’s forces. Gravity and Electro-Magnetism start pulling dust together. Electrostatic Attraction gets small particles to stick together at first, and when they reach a certain minimum combined mass, gravity takes over from there as the dominating ‘growth driver’. From there it’s just a function of time, location, and available material.

    Watch Cosmos.

  4. Think “Ice’ as in frozen liquids, not Ice as in frozen water. It’s a bunch of rocky debris that gathered under its own gravity and froze together in space with equally cold (think really close to absolute zero) gas molecules (co2, methane, ammonia, etc.). In space, the lack of air between the particles lets them find enough molecular bonding points to sort of stick together, like you would get if you had two really flat surfaces and slid them together-what they call vacuum welding. So, this collection of junk ends up making a kind of rock, like an asteroid, and, if it’s orbiting a star, when it gets close enough, light and solar wind heat it up to where those same gasses start to melt, then boil. It’s in space, no gravity, right? So the gas goes out in all directions. If it’s BIG enough, it obscures/picks up enough sunlight that it appears as a cloud from far away. Since the suns light and solar wind has pressure, this cloud is “blown” away from the Sun, which is why a comets tail always points away from the Sun, not away from the direction of travel. Eventually, after enough passes around a star, the comet loses enough cohesiveness or gets small enough that just falls apart and, without outgassing, becomes nearly invisible.

  5. The elements came from a supernova before the sun was born. After the supernova, the material began swirling around and collecting. The supernova before the sun produced a lot of oxygen which mixed with hydrogen to make water. Since they were far from our sun, they froze together to make icy comets.

  6. I’ll do my best to remember what I can from Astronomy 150.
    Water-ice can only exist, In our solar system as a solid, outside the snow-line. This snow line lies roughly at 3.8 AU from the sun, any water ice that comes inside that line will quickly evaporate into gas. When we see comets from earth, this is exactly what we are seeing, water evaporating off the comets surface.
    Comets form on the very edges of our solar system in a giant sphere called the Oort Cloud. They form by accretion, gravity forcing smaller objects together to form bigger ones. Thus, since the only material in the Oort Cloud is dust and particulate water-ice, comets are mainly composed of just that.
    Comets have massive orbits. Hence why we only see some comets once every few decades. However, each time they enter the snow line, they loose a little bit of mass. Eventually, after entering the snow line over, and over, comets perish. They either disintegrate or, in the case as of recent with the comet Io, they travel too close to the sun and are burned up completely.

    Sorry for grammar or spelling errors. Typed this out on my phone.

    Source: Memory from Astronomy 150

  7. Comets formed along with everything else in our solar system. They are the left over material made up of frozen matter, and can vary in composition. Comets have a dark surface made up mostly of carbon, think of a hard candy shell. What is inside of the comet, depends on how old it is and its distance to the sun. Most of the time, the comet has a frozen solid chunk of matter on the inside, but as it begins falling towards the sun it goes through a process called sublimation. This is when the solid chunk of matter skips the liquid phase and turns directly into gas. Gas is less dense than solid and the comet starts ejecting the gas. That is how comet trails are formed and why there might be water traveling around the comet.

    Now if you wondering how water is even present in the comet, that’s a much bigger answer that involved the life cycle of stars.

  8. Three important things:

    Water is thought to be common throughout the universe. So, there’s likely a fair bit of it in a pre-star nebula scattered about. The water is made during supernovae where there is plenty of energy, hydrogen, and oxygen around.

    Water molecules will attract to each other due to gravity and their polar electromagnetic composition. This explains how comets can form in space.

    During the formation of a solar system, areas close to the sun where rocky planets form is too hot for liquid water. What happens is the forming star heats up the water near the star to more than the water’s gravity or electromagnetic attraction can keep it together. The added heat generally pushes the water away from the sun. If/when the water is in a cooler part of the solar system it will condense, and start attracting to each other. You get asteroids with water, planets with water (like Uranus), and also just icy things like Pluto or comets way out there.

    Here’s a question that we haven’t quite answered yet, though. If the inner area of a solar system is too hot for water to coalesce, where did Earth’s water come from? We don’t know for sure. Our best guess is that asteroids or comets brought water to the planet after Earth’s formation.

  9. is the question related to why is there water at all in the comet-making part of the solar system? what created all that water? is possible that there was lots of water throughout the disc that surrounded the proto-Star and only the water far away was able to survive the solar-system making process because of the temperature or other processes? did earth’s water collect together from this water that was everywhere, or did that water burn off and earth’s oceans were delivered to it by comets? i get that comets have ice because its cold in the oort cloud.. but why water? is that the question that is being asked? as opposed to solid etOH or whatever.

    don’t comets also have the basic organics and amino acids and they are all the left-handed versions as well that we find so many of here on earth? isn’t that a rather cool thing? comets can pepper a planet with all the necessary ingredients for life to start up.

  10. So people are saying that comets form out of dust from electrostatic and gravitational attractions, but how does a small ball of dust become a solid rock from just those two things? It seems that a large body like a planet or star can accomplish this throught its large gravitational forces, but why isn’t a comet just a loosely bound clump of dust?

  11. Comets and asteroids are leftover planetismals that never accreted into planets. About 4.5 billion years ago, the nebula from which we spun out began to collapse, probably as a result from a supernova shockwave. This nebula was about 98% H and He, 1.4% H-compounds (water, ammonia, ethane), .4% rocks and minerals and 2% metals. Now, H and He are gasses in space and gasses cannot build planetismals. Most of the remaining material was H-compounds. The center of collapse (to become our sun one day) was hot. Around 5AU away, the temperature was cool enough for the H-compounds to become solid. There’s more than twice as much “ices” as there is metals and minerals. This is where comets formed and this is why they have water. They formed in a region where it was cool enough for H-compounds to become solid. Inside of this region is where the rocky asteroids and, later, the terrestrial planets formed.

  12. Basically billions of years ago Jupiter and Neptune became a 2:1 resonance which basically threw all of the rocket bodies inwards and the icy bodies outwards. Between Mars and Jupiter there is a think called a snow ice line where anything formed outside is of ice and snow. Basically over billions of years the snow and Ice pieces slowly begin to accrete to each other (stick together by gravity) and over time become larger and larger and create comets.

  13. It’s simple really. Supernova nucleosynthesis creates the “soup” that solar systems are built off of. When a star goes supernova, these elements are sent outward into the cosmos, creating great big clouds of gas and dust, which are basically just mixtures of these elements. Gravity takes over, the gas and dust clumps, and begins to spin. The spin causes a flat disc to form, and at the center, gravity continues to build a protostar. Enough gravity and pressure, and hydrogen atoms begin to fuse, creating helium. After a while, the fusion takes over, and you have a star. The remaining gas and dust is then projected outward. This gas and dust in turn clumps under gravity as it orbits the new star. The farther out you go, the less likely these clumps find each other (in the Oort cloud, each object is as far away from each other as Earth is to the sun.) There’s also less heat, so water stays frozen. Comets are basically a mixture of all kinds of things, but water is a common element, and so it happens to be part of them. Notice: water is not just “on” comets, it exists throughout the clump, along with many other elements.

  14. Earth has so much water from luck. No joke.
    And comets can be form from many things.
    * Stars exploding (Gravity and unstable cores help on that),
    * heavy impacts by other comets may cause parts of the “body”/planet to detach creating other comets
    * or they just lucky keep drifting in the void of space from the big bang.
    This is the general idea. Hope i didn’t confused you further.

  15. Comets are primordial debris from the original existence of the solar system. They may also include a percentage of captured objects from interstellar space. They exist because the cross section of interaction with other objects inside the solar system is reduced, both by comets long orbital period and short portion of their lifespan near the sun, and the fact that the inner solar system has largely been cleared of gas and most objects for several billion years. The Jovian planets clear the inner solar system.

    In some ways the question of how did comets form is, “why are there so few things orbiting the sun with highly elliptic orbits and why are they all icy?” Comets are mostly icy and they’re in long period orbits that graze the sun.

    The dust and clumps of gas inside the orbit of Jupiter mostly formed into rocky planets, not because rock is attracted to rock, but because most of the lighter gases evaporated away. Those volatiles were only able accumulate in the outer part of the solar system in Jupiter, Saturn, Uranus and Neptune and their moons and trojans. As Jupiter formed it established a sequence of resonant modes with the other planets and the asteroids. Almost all the bodies in our solar system, the inner planets, trojan satellites, moons and asteroids inside the orbit of Saturn have some type of resonant behavior associated with a Jovian sized planet. Everything that isn’t in a type of stable relationship gets tossed out and eventually impacts a planet.

    So the long term history of our solar system has left rocky planets near the sun, gas giants further out and lots of rocks, asteroids, trojans and moons locked in resonant orbits. Comets are what’s left over from the original forming of the solar system. There just the lucky strange rogues that never were able to impact enough junk early on to shed their ellipticity and get stuck in the inner or gas giant part of our system. If they had they would have become resonant locked with something or fall into a planet. The long period ones probably aren’t in resonance with a Jovian planet, they don’t get near the sun for long enough to boil off their water so they stay icy. They have ice because they don’t have enough gravity to retain more volatile gases like Hydrogen.