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39

Sorry for the length of this, but it brings up some interesting facts and possibilities. The moons you mention, Titan, Europa, and Enceladus, are three very different places. Titan has a relatively large surface gravitational acceleration (as far as satellites go) and a very thick atmosphere; Europa has a relatively large surface gravitational acceleration ...


28

Simple. It was the easiest to land on. Titan has an atmosphere, which makes landing there quite a bit easier than landing on Europa, which does not. In addition, Europa has only been known as an object of interest since Galileo, which was the last mission that even had a chance of sending a lander there. It was suspected as an object in the Voyager flyby, ...


25

In order for a combustion process to happen, you do not only need fuel, you also need an oxidizer. On Earth, that is usually the oxygen in the air. In Titan's atmosphere, there is no oxygen. This applies to other atmospheres too, like the hydrogen dominated atmospheres of Jupiter and Saturn. Hydrogen, just like the methane in Titan's atmosphere, is flammable ...


23

A -183 C nitrogene-methane mix doesn't make you an icecube on the spot, but it still causes quickly frozen wounds. Your only way to avoid it if your whole body is protected, no $cm^2$ may remain open. You need also oxygen supply. Here comes another problem: methane with oxygen supply becomes an explosive substance. The methane concentation on the Titan's ...


22

The mass of Titan is 1,345 · 1023 kg, but the mass of the Moon is 7,349 · 1022 kg. The gravity at the surface is 1,35 m/s² for Titan and 1,62 m/s² for the the Moon. But the surface temperatures are very different, 94 K for Titan but the mean surface temperature of the Moon is 218 K and the peak about 300 K. Due to the high surface temperature of the Moon,...


22

The ESA Huygens probe very accurately characterized the conditions at its landing site on Titan's surface and verified measurements made by the Voyager 1 Radio Science (VRS) investigation nearly 25 years earlier. It measured a surface temperature of 93.8K (VRS: 94.0 ± 0.7 K), a surface pressure of 1467 mb (VRS: 1496 ±20 mb), a methane abundance of 5.65 ± 0....


21

Based on saturation diving operations, it looks like the limits are as follows: Compressed air: Nitrogen narcosis limits you to around four times Earth's atmospheric pressure. Any gas mix: Hydreliox was used for the current depth record; insomnia and fatigue issues appear to limit you to around 65 times Earth's pressure regardless of gas mix. Neither Titan ...


18

It's probably going to be less of a concern than you'd guess. The icy worlds of our solar system have essentially no atmosphere, so the surface materials will sublimate directly to vapor and be dispersed rather than melting and freezing the landing pads into place. Fairly little of the surface will be disturbed to begin with. The gas expansion which ...


13

This article suggests that the radar can penetrate the lakes and reports them to be hundreds of meters deep. The space.com article referenced seems to be sourced from a Geophysical Research Letters article from 2008 (not paywalled) which gives the radar wavelength (2.2cm) and claims that it would be absorbed in 2-20m of clean hydrocarbon, but also give other ...


12

A colleague worked on the Titan Mare Explorer (the concept did not proceed beyond proposal stage). It was an ultra-cool idea that would include to lower a boat to sail the seas of Titan (doesn't that sound catchy?). Alas, it wasn't selected; instead, NASA selected the InSight Mars lander — NASA keep changing their priorities as to where they want to go. ...


11

Titan's atmosphere is not extremely thick. Its only 1.5 bars at ground level. Its also not corrosive, consisting mostly of nitrogen and, to a lesser degree, methane. The only real challenge is the distance from the sun. Reaching Titan requires a considerable amount of delta-v (about 20km/s from the earth's surface). Once you are on Titan, solar panels are ...


10

It is not being overlooked. There are studies which are being carried out about the feasibility of life on Titan based on methane. It is true that Titan has all the necessary conditions for life: It is not in thermodynamic equilibrium It has more than enough of carbon based molecules It has a fluid environment (ethane/methane) for chemical reactions to ...


9

The solar flux at 1 AU (Earth's distance from the sun) is ~1361 W/m2. Flux falls off as the square of distance. Saturn, on average -- and thus Titan, on average -- is about 9.58 AU from the sun, so the falloff factor is 1 / 9.582 or 0.0109. Titan should average about 1361 x 0.0109 = 14.8 W/m2 when not shadowed by the gas giant. When Saturn is at its ...


8

Let's turn the question on its head and see what exhaust velocity we need to if Titan's entire (mostly nitrogen) atmosphere were used as a propellant. $\Delta v = v_e log(m_i / m_f)$ Wikipedia tells us that the atmosphere of Titan is about 1.19 times as massive as that of Earth so we get about 6.13e18 kg of atmosphere (propellant) in a total mass of about ...


7

Let's do a Fermi estimate: Rockets bring about 2-5% of their start mass to orbital velocity. To cancel out Titan's orbital velocity, you're looking at two orders of magnitude more fuel and oxidizer than Titan's mass. Earth's atmosphere weighs $10^{18}$ kg, or 1/200,000 of Earth's total mass. Titan's is 1.5 times as dense, so if Titan's atmosphere were ...


7

Tholins encompass a large range of hydrocarbon compounds, could be anything from heavy oil-like substances to something more akin to plastics. So it'll burn, the question is if you can use it in an engine. Heavy oil needs a large engine, plastics aren't really usable. There are two ways around this: either burn the tholins directly and build a steam ...


7

It's a late answer but I was surprised nobody cited this: Titan Mare Explorer (TiME) The TiME lander was a part of cooperative NASA-ESA mission TSSM. The mission was not considered as highest priority by Planetary Decadal Survey 2013 so it's not being implemented now. Also it was studied as standalone Discovery class mission. ASRG generator was planned as ...


7

The maximum pressure for long term survival in an atmosphere of 79 % nitrogen and 21 % oxygen is limited by oxygen toxicity. The limit of the partial pressure of oxygen is about 0.5 bar, the maximum pressure therefore is about 2.5 bar. For only some hours the pressure may be 4 to 5 bar, but nitrogen narcosis might be a problem. For higher pressures the ...


7

In general, a spectrum can tell us about the composition of the source of the radiation, or of any substance between the source and the detector. Each material has its own fingerprint and spectroscopy allows us to decompose this in constituent parts. Shorter wavelengths will likely saturate NIRSpec, especially at lower resolutions Without having studied ...


7

The spectrum you show from Titan was taken using the IRIS spectrometer aboard Voyager 1. Of course Voyager 2 had one as well. A huge amount of work went into developing and optimizing the design in order to develop a precise optical instrument that would survive both the high g-force and vibrations of launch, and the years in a space environment while ...


6

The Huygens probe that landed on Titan back in 2005 had a special flood-light affixed to its cameras because it's supposedly too dark to take pictures with any detail during Titans day without it. Images from the DISR Side-Looking Imager and from the Medium Resolution Imager, acquired after Huygens' landing on Titan, were merged to produce this image. ...


6

Additional to @Rikki's answer in addition to heat and power you need to be able to move and explore, there are several challenges to this: Titan is far from the sun, so has very little light. On Mars there's enough light for conventional camera instruments to work. Making navigation decisions is possible based mostly on visual information. On titan you'd ...


6

NASA's currently planned and funded (to some extent) future missions are listed here: http://www.nasa.gov/missions/future/. Alas, nothing is currently planned for Titan. I guess other agencies/organizations might have something.


6

The Phys.org article Researcher sets eyes on Saturn's largest moon describes the Dragonfly project; the potential application of large (~2 meter) quadcopters on Saturn's moon Titan. Dragonfly is one of two NASA recently short-listed– from an original proposal group of a dozen – as part of the agency's New Frontiers planetary science program. An artist’...


6

A quick search on Google Scholar turns up 106 articles published in 2018 using Huygens' data. So I'd say the data is still being analyzed and used.


6

As noted before, landing gear, especially for soft or relatively rough surfaces, tends to be heavy, and mass is at a premium. More on that later. But there is another good reason to stay aloft, especially if the craft can fly at more than ~12 m/s, which is Titan's equatorial rotation speed (11.744 m/s): you can stay on the Earth-facing side of Titan, so you ...


6

According to NASA's article "Rainbows on Titan": The density of liquid methane is only about half the density of water. This is something, say, a boat builder on Titan would need to take into account. Boats float when they're less dense than the liquid beneath them. A Titan-boat would need to be extra lightweight to float in a liquid methane sea. ... ...


6

No, liquid methane in a nitrogen atmosphere is not a useful fuel. Earth is a very special place to have such a reactive substance as oxygen abundantly in the atmosphere, and that's only because plants are constantly generating it from carbon dioxide using solar power. Without some process like that, any combination of chemicals that you could burn to make ...


6

Given that they are finding water in all sorts of places, my bet is on Enceladus and Mars. But here's a few interesting quotes I gathered from NASA... From Water: Life's Elixir in the Solar System: Liquid water is a necessity for every form of life known, with the possible exception of some plants or fungi that may get by on water vapor. With this ...


6

Wikipedia says of the composition of the lower atmosphere: Because methane condenses out of Titan's atmosphere at high altitudes, its abundance increases as one descends below the tropopause at an altitude of 32 km, leveling off at a value of 4.9% [the rest is mostly nitrogen] between 8 km and the surface. and in a separate article The average ...


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