Titan is the most hospitable extraterrestrial world

Titan is the most hospitable extraterrestrial world within our solar system for human colonization." ^[6] The atmosphere contains plentiful nitrogen and methane, and strong evidence indicates that liquid methane is on the surface and, liquid water, and ammonia are present under the surface and are often delivered to the surface by volcanic activity. HP Pavilion DV7-3165dx laptop keyboard

Water can easily be used to generate breathable oxygen. Nitrogen is ideal to add buffer gas partial pressure to breathable air; indeed, nitrogen forms about 78% of Earth's atmosphere.^[7] Nitrogen, methane and ammonia can all be used to produce fertilizer for growing food.

Additionally, Titan has an atmospheric pressure one and a half times that of Earth. SONY VAIO VGN-NW25GF laptop keyboard

This means that the interior air pressure of landing craft and habitats could be set equal or close to the exterior pressure,reducing the difficulty and complexity of structural engineering for landing craft and habitats compared with low or zero pressure environments such as on the Moon, Mars, or the asteroids. Compaq Presario CQ71-317EA laptop keyboard

The thick atmosphere would also make radiation a non-issue, unlike on the Moon, Mars, or the asteroids. While Titan's atmosphere does contain trace amounts of hydrogen cyanide, in the event that an astronaut's respiration system is breached, the concentration would not inflict more than a slight headache. HP Pavilion dv6-2129ev laptop keyboard

A greater danger is that the gases of the atmosphere can generate an explosive mixture with oxygen, which requires special measures in the event that a leak occurs in a habitable module or a spacesuit.

Titan has a surface gravity of 0.14 g, slightly less than that of the Moon. FUJITSU Lifebook P1610 laptop keyboard

Managing long-term effects of low gravity on human health would therefore be a significant issue for long-term occupation of Titan, more so than on Mars. These effects are still an active field of study. They can include symptoms such as loss of bone density, loss of muscle density, and a weakened immune system.SONY VAIO VGN-FS640/W laptop keyboard

 Astronauts in Earth orbit have remained in microgravity for up to a year or more at a time. Effective countermeasures for the negative effects of low gravity are well-established, particularly an aggressive regime of daily physical exercise or weighted clothing. The variation in the negative effects of low gravity as a function of different levels of low gravity are not known,  HP 405963-001 laptop keyboard

since all research in this area is restricted to humans in zero gravity. The same goes for the potential effects of low gravity on fetal and pediatric development. It has been hypothesized that children born and raised in low gravity such as on Titan would not be well adapted for life under the higher gravity of Earth.  HP Pavilion G6-1223TX Laptop Keyboard

The temperature on Titan is about 94 K (−179 °C, or −290.2 °F), so insulation and heat generation and management would be significant concerns. Although the air pressure at Titan's surface is about 1.5 times that of Earth at sea level, because of the colder temperature the density of the air is closer to 4.5 times that of Earth sea level. HP Pavilion dv6-3001so laptop keyboard

At this density, temperature shifts over time and between one locale and another would be far smaller than comparable types of temperature changes present on Earth. The corresponding narrow range of temperature variation reduces the difficulties in structural engineering.

Relative thickness of the atmosphere combined with extreme cold makes additional troubles for human habitation. HP HDX18-1100 CTO laptop keyboard

Unlike in a vacuum, the high atmospheric density makes thermoinsulation a significant engineering problem.

The very high ratio of atmospheric density to surface gravity also greatly reduces the wingspan needed for an aircraft to maintain lift, so much so that a human would be able to strap on wings and easily fly through the atmosphere.^[6] SONY VAIO VGN-N21E/W laptop keyboard

However, due to Titan's extremely low temperatures, heating of a flight-bound vehicle becomes a key obstacle.

The lakes of Titan, a moon of Saturn, are bodies of liquid ethane and methane that have been detected by theCassini–Huygens space probe, and had been suspected long before.^[2] HP Pavilion dv5-1118tx laptop keyboard

The large ones are known as maria (seas) and the small ones as lacūs (lakes).

The possibility that there were seas on Titan was first suggested based on Voyager 1 and 2 data. The data showed Titan to have a thick atmosphere of approximately the correct temperature and composition to support them. HP AEUT5U00010 laptop keyboard

Direct evidence was not obtained until 1995 when data from the Hubble Space Telescope and other observations had already suggested the existence of liquid methane on Titan, either in disconnected pockets or on the scale of satellite-wide oceans, similar to water on Earth.^[4]

The Cassini mission affirmed the former hypothesis, although not immediately. HP Mini 110-3504tu laptop keyboard

When the probe arrived in the Saturnian system in 2004, it was hoped that hydrocarbon lakes or oceans might be detectable by reflected sunlight from the surface of any liquid bodies, but no specular reflections were initially observed.^[5]

The possibility remained that liquid ethane and methane might be found on Titan's polar regions, where they were expected to be abundant and stable.^[6] SONY VGN-FE21H laptop keyboard

 In Titan's south polar region, an enigmatic dark feature named Ontario Lacus was the first suspected lake identified, possibly created by clouds that are observed to cluster in the area.^[7] A possible shoreline was also identified near the pole via radar imagery.^[8] Following a flyby on July 22, 2006, in which the Cassini spacecraft's radar imaged the northern latitudes  HP G72-b60SF laptop keyboard

 (which were at the time in winter), a number of large, smooth (and thus dark to radar) patches were seen dotting the surface near the pole.^[9] Based on the observations, scientists announced "definitive evidence of lakes filled with methane on Saturn's moon Titan" in January 2007.^[6][10] HP Mini 110-3180sv laptop keyboard

The Cassini–Huygens team concluded that the imaged features are almost certainly the long-sought hydrocarbon lakes, the first stable bodies of surface liquid found off Earth. Some appear to have channels associated with liquid and lie in topographical depressions.^[6] Channels in some regions have created surprisingly little erosion, LENOVO IdeaPad S10 20015 laptop keyboard

suggesting erosion on Titan is extremely slow, or some other recent phenomena may have wiped out older riverbeds and landforms.^[11] Overall, the Cassini radar observations have shown that lakes cover only a few percent of the surface and are concentrated near the poles, making Titan much drier than Earth.^[12] HP Mini 110-3180sv laptop keyboard

 The high relative humidity of methane in Titan’s lower atmosphere could be maintained by evaporation from lakes covering only 0.002–0.02% of the whole surface.^[13]

During a Cassini flyby in late February 2007, radar and camera observations revealed several large features in the north polar region interpreted as large expanses of liquid methane and/or ethane, Lenovo ThinkPad Edge E125 laptop keyboard

including one sea (Ligeia Mare) with an area of over 100,000 km² (larger thanLake Superior), and another incompletely imaged region potentially the size of the Caspian Sea (Kraken Mare).^[14] A flyby of Titan's southern polar regions in October 2007 revealed similar, though far smaller, lakelike features.^[15] HP Pavilion dv6-3230us laptop keyboard

Image of Titan taken duringHuygens' descent, showing hills and topographical features that resemble a shoreline and drainage channels.

During a close Cassini flyby in December 2007 the visual and mapping instrument observed a lake, Ontario Lacus, in Titan's south polar region. ACER K052030A1 laptop keyboard

This instrument identifies chemically different materials based on the way they absorb and reflect infrared light. Based on this instrument's observations, scientists concluded that at least one of the large lakes observed on Saturn's moon Titan does in fact contain liquid, that liquid being hydrocarbons, and have positively identified the presence of ethane.  DELL Inspiron 6400 Laptop Keyboard

And on July 8, 2009, a specular reflection in infrared was seen off Jingpo Lacus, a lake near Kraken Mare. This confirms the presence of liquid on the part of the moon dotted with many large, lake-shaped basins, in the northern regions of Titan.^[16] This makes Titan the only other object than Earth in the solar system known to have stable liquid on its surface.^[17] TOSHIBA NSK-TAJ01 Laptop Keyboard

This would make Titan a very interesting place to observe and study, to refine weather science, as differing liquid and gaseous materials and temperatures are at play there. This would help refine the science of Earth weather forecasting, allowing for better weather forecasts.^[ Radar measurements made in July 2009 and January 2010 indicate that Ontario Lacus is extremely shallow, ACER Aspire 7741G Laptop Keyboard

with an average depth of 0.4–3.2 m, and a maximum depth of 2.9–7.4 m.^[18] It may thus resemble a terrestrial mudflat. In contrast, the northern hemisphere's Ligeia Mare has depths exceeding 8 m, the maximum measurable by the radar instrument.

According to Cassini data, scientists announced on February 13, 2008, SONY KFRMBA152B Laptop Keyboard

that Titan hosts within its polar lakes "hundreds of times more natural gas and other liquid hydrocarbons than all the known oil and natural gas reserves on Earth." The desert sand dunes along the equator, while devoid of open liquid, nonetheless hold more organics than all of Earth's coal reserves.^[19] HP Pavilion dv6-3001so Laptop Keyboard

In June 2008, Cassini's Visible and Infrared Mapping Spectrometer confirmed the presence of liquid ethane beyond doubt in a lake in Titan's southern hemisphere.^[20] The exact blend of hydrocarbons in the lakes is unknown. In addition to ethane, methane is almost certainly present. Methane rain should fall on the lakes but it is vastly more volatile than ethane, HP HDX18-1100 CTO Laptop Keyboard

so it probably evaporates much faster from lakes, leaving the heavier hydrocarbons behind. Cyclonesdriven by this evaporation and involving rain as well as gale-force winds of up 20 meters per second are expected to form over the large northern seas only (Kraken Mare, Ligeia Mare, Punga Mare) in northern summer, lasting up to ten days.^[21]  TOSHIBA Satellite C655-S9521D Laptop Keyboard

According to a computer model developed by Daniel Cordier of the University of Rennes, three-quarters of an average polar lake is ethane, with 10 per cent methane, 7 per cent propane and smaller amounts of hydrogen cyanide, butane, nitrogen and argon. The chemical composition and physical properties of the lakes probably varies from one lake to another. HP G42-380LA Laptop Keyboard

The lack of evidence of waves possibly indicates the lakes contain heavier tar like hydrocarbons making them more viscous than expected (calculations indicate wind speeds of less than 1 metre per second should whip up detectable waves in Titan's ethane lakes but none have been observed).^[22] In such a case, GATEWAY NV-53 Laptop Keyboard

Titan's lakes are rather more like giant tar pits. Another possible explanation would be solidification of hydrocarbons. The optical properties of solid methane surface (close to the melting point) are quite close to the properties of liquid surface however the viscosity of solid methane, even near the melting point, is many orders of magnitude higher, which might explain extraordinary smoothness of the surface.^[23]  HP 646568-001 Laptop Keyboard

Solid methane is denser than liquid methane so it will eventually sink. However, according to calculations presented in a 2012 paper by Jason Hofgartner^[24] the methane ice is initially expected to float as it probably contains pockets of nitrogen gas from Titan's atmosphere. Temperatures close to the freezing point of methane (90.4 Kelvins) could lead to both floating and sinking ice - t ACER Aspire One D150-1920 Laptop Keyboard

hat is, a hydrocarbon ice crust above the liquid and blocks of hydrocarbon ice on the bottom of the lake bed. The ice is predicted to rise to the surface again at the onset of spring before melting.

On 21 December 2008, Cassini passed directly over Ontario Lacus at an altitude of 1900 km and was able to observe specular reflection in radar observations. HP AEUT5U00010 Laptop Keyboard

The signals were much stronger than anticipated and saturated the probe's receiver. The conclusion drawn from the strength of the reflection was that the lake level did not vary by more than 3 mm over a first Fresnel zone reflecting area only 100 m wide (smoother than any natural dry surface on Earth). From this it was surmised that surface winds in the area are minimal at that season and/or the lake fluid is more viscous than expected.^[25][26] ACER Aspire One D150-1920 Laptop Keyboard

On 8 July 2009, Cassini's Visual and Infrared Mapping Spectrometer (VIMS) observed a specular reflection in 5 micron infraredlight off a northern hemisphere body of liquid at 71° N, 337° W. This has been described as at the southern shoreline of Kraken Mare,^[27] but on a combined radar-VIMS image the location is shown as a separate lake (later named Jingpo Lacus).  HP AEUT5U00010 Laptop Keyboard

The observation was made shortly after the north polar region emerged from 15 years of winter darkness. Because of the polar location of the reflecting liquid body, the observation required a phase angle close to 180°.

The discoveries in the polar regions contrast with the findings of the Huygens probe, which landed near Titan's equator on January 14, 2005. APPLE A1278 Laptop Keyboard

The images taken by the probe during its descent showed no open areas of liquid, but strongly indicated the presence of liquids in the recent past, showing pale hills crisscrossed with dark drainage channels that lead into a wide, flat, darker region. It was initially thought that the dark region might be a lake of a fluid or at least tar-like substance, ACER 9J.N0F82.A1D Laptop Keyboard

but it is now clear that Huygens landed on the dark region, and that it is solid without any indication of liquids. Apenetrometer studied the composition of the surface as the craft impacted it, and it was initially reported that the surface was similar to wet clay, or perhaps crème brûlée (that is, a hard crust covering a sticky material). HP G72-b66US Laptop Keyboard

Subsequent analysis of the data suggests that this reading was likely caused by Huygens displacing a large pebble as it landed, and that the surface is better described as a "sand" made of ice grains.^[29] The images taken after the probe's landing show a flat plain covered in pebbles. The pebbles may be made of water ice and are somewhat rounded, which may indicate the action of fluids.^[30] ACER 9J.N0F82.A1D Laptop Keyboard

Thermometers indicated that heat was wicked away from Huygens so quickly that the ground must have been damp, and one image shows light reflected by a dewdrop as it falls across the camera's field of view. On Titan, the feeble sunlight allows only about one centimeter of evaporation per year (versus one meter of water on Earth),  HP G72-b66US Laptop Keyboard

but the atmosphere can hold the equivalent of about 10 meters of liquid before rain forms vs. only a few centimeters on Earth. So Titan's weather is expected to feature torrential downpours causing flash floods, interspersed by decades or centuries of drought.^[31] Cassini has observed equatorial rainstorms only once since 2004. HP Mini 110-3180sv Laptop Keyboard

Despite this, a number of long-standing tropical hydrocarbon lakes were unexpectedly discovered in 2012 (including one near the Huygens landing site in the Shangri-La region which is about half the size of Utah's Great Salt Lake, with a depth of at least 1 meter). As on Earth, the likely supplier is probably undergroundaquifers, in other words the arid equatorial deserts of Titan contain "oases".^[32] Lenovo 3000 N200 Laptop Keyboard