Hot answers tagged

87

It depends on where in outer space you are. If you simply stick it in orbit around the Earth, it'll sublimate: the mean surface temperature of something at Earth's distance from the Sun is about 220K, which is solidly in the vapor phase for water in a vacuum, and the solid-vapor transition at that temperature doesn't pass through the liquid phase. On the ...


15

Its very unlikely for a comet to become a satellite of an inner solar system planet. Much less likely than it is for an asteroid. Most asteroids are on fairly circular orbits, and so the relative velocity between asteroids and planets is quite low. In comparison comets have very elliptical orbits, and their relative velocities to the planets are much larger. ...


12

It would sublimate. The frozen mass of water would decrease in size as the water converts from a solid to a gas (without becoming a liquid) and drifts away.


10

Given that moons commonly orbit planets, why do we never encounter a comet orbiting a planet? By definition, it would no longer be a comet, but rather a moon (or more properly a satellite). Comets are icy bodies that orbit the Sun, satellites are any body which orbits a larger body than itself, other than the Sun. There are many examples of asteroids and ...


10

Technically those aren't "geysers" on Europa, they're cryovolcanos. Though that definition may be a bit imprecise as well, but the 100 km eruptions on Europa probably have more in common with volcanic eruptions on Earth than geysers. Europa undergoes significant tidal flexing which, in combination to it's solid icy crust, could be compared to explosive ...


10

The key finding why we think Earth's water came from Asteroids (big rocks) and not Comets (small rocks) is the Deuterium/Hydrogen ratio that we can measure in several sources. When a star forms, it has an initial value of D/H that came from the nucleosynthesis in its progenitor nebular / star. In a protoplanetary disc, as dust grows to rocks grow to planets ...


9

Liquid water can in principle exist at many locations on present-day Mars, but there are a few interesting twists to the story. At low elevation, the atmospheric pressure is high enough. The triple point pressure of H2O is 611 Pascal, which corresponds to about mid-elevation. At low elevations, such as the northern lowlands, the atmospheric pressure will ...


8

Some of the water evaporated, some of it froze and another good part of it went into the surface and is now subterranean. For more info read Mars' Vanished Water & Atmosphere --Where Did It Go? and MAVEN’s Quest – Where Did Mars Water Go?. There's much still to learn and experiments in the future will help us to better understand the evolution of Mars' ...


8

We can look up for water in the atmosphere of the planet, not at the planet itself. We can do that when a planet passes in front of a star. That tehnique is called transmission spectroscopy.


8

Self-sufficiency is an incredibly broad term. We could argue that yes, there is water on the Moon, and that yes, there are viable ways to produce required electricity in self-sustainable ways, but the real question is, are there areas on the Moon that would be viable for both at the same time. You see, the most likely place where surface or near subsurface ...


7

Any ice that forms from water will be free of salt -- the process of crystallization does an excellent job of removing impurities. But that's only when freezing out of liquid water, which is not a process that happens today at the Martian surface. When ice forms out of the air, it forms as tiny crystals -- "hoar frost" we call it on Earth -- and forms on ...


6

I wanted to throw my hat into the mix to flesh out another contributing factor. One reason these "geysers" are so capable of achieving great heights is a lack of atmosphere on Europa to slow them down (and to a lesser extent, weaker gravity). I wrote a basic "physics simulation" in Python 3 which illustrates this purpose, the code for which is below. import ...


5

No and yes. I'll address the "no" answer first. The answer is no if you truly mean "water ice". Ceres is close to the limit of where water can exist as water, as opposed to in the form of hydrated rock. Those intriguing bright spots on Ceres may well be water ice that has been exposed to vacuum (but they might just be salts). Ceres most likely is inside the ...


5

Unlikely. Plugging numbers into the Stefan–Boltzmann law gives us a temperature near 273°K (0°centigrade) for bodies near earth's orbit. The exact answer for atmospherless bodies depends on albedo. Any water on nearby asteroids will thus boil until it freezes, and then sublimate. That's why the search for nearby ice is focused on lightless, cold regions of ...


5

In the vacuum of space the most important consideration is to consider how much radiation an ice cube would absorb from, for example, nearby stars and how fast the ice cube itself would radiate away energy (using Wien's law), finding what ice cube temperature would produce an equilibrium (the temperature at which the ice cube radiate energy at the same rate ...


5

First, one should observe that water is very abundant in the Solar system and most of it comes from before the planetary formation stage. Even Mercury has got its deal of water, albeit a small one. I think, it will be safer to assume that earth had had it water from the very beginning of its formation. Additional thing to consider are the temperatures, ...


5

No idea is stupid per se. But in order to place an answer to your question, please consider Venus as a comet. It once had, in that image, a coma (a tail) pointing outwards from the sun, made of evaporated water pushed away by solar wind. How frequently is the Earth exactly inside that coma? As a comparison, when the Earth strikes a real comet coma we see ...


5

Had you asked a couple of months ago the answer would be "probably yes", now it is more "maybe". Pure water could not exist in the Martian Environment. The pressure is too low, so the water would turn to water vapour. Yes, if you produce hyper-concentrated brine it can remain in liquid form for a while in some martian environments. Solutions of ...


5

It looks to me that you probably have some misunderstanding of the term meteorite. A meteorite is a remnant body which has reached the surface of a major or minor body (a planet, a moon, an asteroid, etc.). The meteorite's parent body (a meteoroid) would definitely lose its entire water ice (if it had any at all) no later than during its passage through the ...


5

According to Wiktorowicz & Ingersoll (2006), Neptune is too hot and too dry to form liquid oceans at the present time. This may seem counterintuitive for a planet with a far higher bulk fraction of water than the Earth which is located so far from the Sun, but the water is going to be mixed up with hydrogen, helium and various other materials in the ...


4

In Farihi et al. (2013) (it's a Science paper, unfortunately I'm not sure its content is freely accessible), they actually measured metal excess in the white dwarf GD 61 (for an astronomer, everything that is nor hydrogen neither helium is a metal). Due to high surface gravity in white dwarfs, any heavy element should sink rapidely in its atmosphere; ...


4

Additionally, Mars has a much more substantial atmosphere composed of ~95% CO2 (which is one of the major points Zubrin makes), whereas the atmosphere of the moon pales in comparison. Why is this important? Combined with the supply of Hydrogen which would be brought along, you could combine the CO2 with H2 to produce methane (CH4) which can be used as rocket ...


4

Yes. See Split comet Shoemaker-Levy 9 became a satellite of Jupiter Ríse hvezd, Vol. 74, p. 224-225 and The Century of Space Science comet Shoemaker-Levy 9 which was probably captured into a Jupiter-centric orbit and thus, temporarily, became a satellite of Jupiter before splitting into at least 21 piece and crashing into Jupiter's atmosphere And ...


4

This is far too soon to draw sweeping conclusions. The Philae probe has only measured deuterium for one comet. But comets are diverse, of diverse origins. We need to take a lot more samples, from many different comets, before we can conclude firmly that water has, or has not, come from comets. The only conclusion we could draw so far from this study is that ...


4

I don't think applying Earth data to Mars makes much sense, well, except perhaps at the very beginning. The reason I say that is that life on Earth took a long time to get what we might consider "interesting", for lack of a better word. Source - and, OK, it's a children's book, but I like the picture. 4 billion years ago - simple cells. 3.5 billion years ...


4

Being an ice giant, there is no water on the surface of Neptune. Having a surface temperature of $-201$ $^oC$ any water on Neptune will be frozen. Extraterrestrial liquid water is believed to be beneath the ice surfaces of the Jovian moons Europa and Ganymede. A sub surface ocean has been confirmed on the Saturnine moon Enceladus. As to whether fish or any ...


3

We have not found life, bacterial or otherwise, anywhere other than Earth ... yet. I think you mean the difference between liquid water and water ice. This difference relates to the hospitality to life. Life of the type we are used to needs liquid water, even if this is just trapped moisture, unless the life is temporarily in suspended animation. If there ...


3

When you talk about the frost line you are talking about a protostar, and its protoplanetary disk, not an actual star. So, there is no empty space nor strong solar winds. Inside the frost line, water does not condense into ice grains, but the individual molecules could as well become attracted by the planets-to-be.


3

I don't believe there is factual answer just yet, though many solid theories. Here are some sources I've found to be helpful. I don't necessarily have an opinion myself and while certainly everyone is entitled to one, I wouldn't put too much stock in any one source of information. It was "always" here: http://news.nationalgeographic.com/news/2014/10/141030-...


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