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45

The Huygens was not capable of transmitting data directly to the Earth, instead Cassini relayed all communication. Therefore mission lifetime was limited by possible communication window from Titan surface to Cassini (which was orbiting Saturn, making only fly-by around Titan and departing the moon soon after the landing). Keeping Huygens alive until Cassini ...


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 ...


23

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....


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

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 ...


20

This book has a table with the energy budget for Huygens: Data relay system: 214 Wh Computer: 246 Wh Electric power system: 5 Wh Payload: 325 Wh Losses: 132 Wh Pre-separation checks: 50 Wh Total: 972 Wh for the designed mission: The batteries and all other resources were sized for a Huygens mission duration of 153 minutes, corresponding to a maximum ...


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 ...


11

Can Dragonfly make it to one of Titan's Lakes? tl;dr: Yes! It could be doable in 2-3 years. According to your linked document Dragonfly will use a Multi-mission radioisotope thermoelectric generator or MMRTG: The MMRTG design incorporates PbTe/TAGS thermoelectric couples (from Teledyne Energy Systems), where the TAGS material is a material incorporating ...


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

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 ...


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

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 ...


7

The paper itself (I have access) says and shows that they are detecting the bottom of some lakes with their radar with a maximum depth of 105+/-6 meters. The radar reflection off the bottom is much fainter than off the surface, but still distinct and clear. The attenuation (17 dB/us) fits a mostly-methane composition (best fit 69% methane, the rest mostly ...


7

From Cassini observations the methane-ethane mixture (with methane by far the largest component, maybe with some dissolved nitrogen) appears so pure that its absorptivity at the RADAR instrument's Ka-band frequency is quite low. That's how it could see so deep — not just 100 m, but 160-170 m. The paper The Bathymetry of a Titan Sea by Marco Mastrogiuseppe ...


7

They plan to use some form of "site evaluation" to prevent tipping over: However, technology developments in the last two decades, notably the revolution in availability of multi- rotor drones a made possible by modern compact sensors and autopilots as well as the development of sensing and control capabilities for autonomous landing and site ...


7

There are bacteria on Earth which get energy from hydrocarbons and oxygen. See for example this article. Many of them need oxygen which is not freely available on Titan. Some (thank's to @Calcutta for pointing this out) can use sulphate as an oxidising agent instead. However, as far as I can find out, essentially all the oxygen on Titan is in the form of ...


7

Cassini's Imaging Science Subsystem produced images like this: which has a resolution of about 200 m/pixel. This is a near-IR image. In visible light, color enhancement can bring out some detail: In UV, the atmosphere is opaque again: The ISS spans IR, visible and UV light: Each camera is outfitted with a large number of spectral filters which, ...


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 ...


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