Hi everyone! So I have an idea for a 'community project' that I think could be a lot of fun if enough people get involved in it! The idea is to explore the science of alien, as a community, through POSITIVE discussions. I myself, have a strong background in chemistry and environmental science, and as a hobby I read a lot about astrophysics and planetary science; it's become a big fascination of mine post-college.
I have a few rules in mind that I would like to ask everyone to follow, but of course I have no authority to ban anyone from this thread... So, honor system, guys!!
1) alien biology is out! This topic I feel has been extensively discussed and expanded on by the community for a LONG time now... I'm more interested in newer topics that not many people have thought about yet.
2) obviously, we can use facts from the movies, but this is not intended to be a discussion/debate on the storyline. Plenty of those threads too. For example, no theories on the mysterious alien 3 egg; that's a storyline debate/discussion.
3) keep it clean! I'd like this to remain a positive and respectful discussion. Let's keep the sarcasm and insults out too, please.
With that all said, I have a topic to get the ball rolling. I'd like to hear any feedback you all may have on this! And definitely feel free to add any tidbits you may have for gaps in my 'theory,' (after all, I'm not a professional planetary scientist or astrophysicist, lol). Also, if you have a similar topic you'd like to add for discussion, please feel free to post it here as well.
We can assume that LV-426 has a surface temperature between -161 °C and -78 °C at the time when the Nostromo set down on the moon. This temperature is EXTREMELY cold, and by the time Hadley's Hope is visited in Aliens, LV-426 must have warmed up considerably; likely as a result of the terraforming process.
We know from our sources (movie/novelization) that LV-426 has an atmospheric composition which contains nitrogen, methane and carbon dioxide crystals. Nitrogen remains gaseous at -195 °C and warmer, and that temperature constraint lies outside the range I've stated before, making this temperature irrelevant. Methane boils at -161 °C, and since we do not see any lakes of methane, we can assume LV-426's surface temperature is warmer than the boiling point of methane. Carbon dioxide crystals are analogous to water-based snow flakes here on Earth. In other words, carbon dioxide crystals are frozen conglomerates of carbon dioxide gas. Carbon dioxide freezes into a solid state at -78 °C, which means LV-426's surface temperature must be colder than the freezing point of carbon dioxide. Additionally, atmospheric pressure is somewhere near that of Earth's or lower, and carbon dioxide does not have a liquid state at any temperature below 5.1 atmospheres of pressure (at sea level, earth is at 1 atmosphere of pressure). We could be conservative, and say that there may be lakes of methane but we just don't see them in the movies; and if this is the case, the temperature range would change to between -195 and -78 °C (since nitrogen is gaseous the temperature must be warmer than the point where it would change to liquid form). Also, it's important to note, that these temperature predictions are assuming the atmospheric pressure is 1 atmosphere; if the pressure is higher or lower then these temperatures would change slightly. These temperatures are cold enough to be supported by Ash's analysis in the movie; "deep cold, well below the line." Obviously, by the time we see Hadley's Hope in the second film the moon has warmed up considerably, thus allowing the characters to roam around outside without protection from the "deep cold." Looking to a moon in our own solar system as an analogy, Titan has a significant amount of methane in its atmosphere. Methane is a green house gas, but about 10 times more effective at trapping heat than carbon dioxide. However, methane reacts with UV-light to form an orange smog which causes an anti-green-house effect blocking out much of the heat from its host star. This is the case on Titan, and explains why the moon is colder than you'd expect considering the amount of methane present in the atmosphere, and further supports the "deep cold" on LV-426. Also, the host star in LV-426's system, Zeta 2 Reticuli, has an abnormally low light intensity for an earth-like main sequence star, as well as abnormally high UV-light emissions for a star of its type. That too would support the "deep cold" description; less light intensity to warm up the moon plus higher amounts of UV-light to react with the atmospheric methane.
During the terraforming process, much of the methane and carbon dioxide would be removed to achieve earth-like levels, and replaced with oxygen. Nitrogen may be removed or added to the atmosphere depending on the original concentrations present (unspecified in the films) to earth-like levels (about 70% nitrogen, 21% oxygen, etc...). By removing the methane, the colonists would be reducing the anti-green house effect caused by methane-UV light induced orange smog. This could possibly allow for LV-426 to warm up enough for the colonists/marines to move around outside without any heavy-duty cold-weather gear or space suits. From an engineering perspective (thinking in terms of efficiency) I'd say LV-426 was a prime candidate for terraforming for two reasons:
1) the high levels of nitrogen already present would have made it less work for the colonists to reach the earth-like 70% atmospheric composition needed.
2) the high abundance of methane would have been an excellent fuel/energy source to power the atmospheric processors which could have directly sequestered the methane from the atmosphere to use. This would also facilitate in the removal of methane in the overall process as well. However, one thing that bothers me about this conclusion regarding the terraforming process is the safety risks associated with it. Here on earth, our atmosphere contains much more oxygen than methane, thus making methane highly combustible (limiting reactant). Going back to Titan, the opposite is true: methane is relatively inert around open flames/heat sources and oxygen (the limiting reactant in this case) would become highly combustible. So, on LV-426, there would be considerable risk for a massive explosion while burning methane as a fuel source (or burning anything at all as fuel for that matter) while pumping out massive quantities of oxygen into the atmosphere.
Geologically speaking, when the characters in the movies describe LV-426 as a "rock," they are implying that there are no vast oceans/liquid bodies on the surface, and it is otherwise incapable of supporting indigenous life without human intervention (terraforming). The movie shows us geysers blasting out some sort of gas. These geysers are likely "ice-geysers" due to the "deep cold," and are forced out from below the moon's surface as a result of frictional warming caused by geological activity. The geological activity would be the result of tidal friction caused by the immense gravitational pull of the gas giant that LV-426 orbits (similar to Jupiter and its moon Io). LV-426 is too small of an object to have any geological activity caused by its own gravity (like earth). Also, since LV-426 is too small to sustain any geological activity from its own gravity, it would be very unlikely that a molten iron/nickel core (or a similar core) would be present to generate a magnetosphere. This would make LV-426 uninhabitable, even after terraforming, because there would be no protection from cosmic radiation or solar winds (which would whisk away any atmosphere, which is what happened/is happening to Mars). However, the gas giant that LV-426 orbits likely generates it's own magnetosphere like Jupiter, which means LV-426 must orbit close enough to the planet to be within its protective magnetosphere, but still far enough away to generate tidal-geological activity without completely covering its surface with constant volcanos (like Io). The gas giant's magnetosphere is likely the result of "metallic hydrogen" which would conduct a magnetic field in the same way earth's molten iron/nickel core does.
The tidally-induced geological activity on LV-426 might suffice as an alternative renewable energy source to power the atmospheric processors at Hadley's Hope rather than sequestering methane from the atmosphere to burn as fuel which would require oxygen to combust anyway (the colonists would be using the oxygen they create to power the processors which create the oxygen to begin with; it would be a cyclical process which would require the technology to be EXTREMELY energy efficient in order to make any progress in supplying breathable amounts of oxygen... Not to mention the hazard involved here).
