Laythe

	Laythe
	Laythe as seen from orbit.
	Moon of Jool
	Orbital Characteristics
Semi-major axis	27 184 000 m
Apoapsis	27 184 000 m
Periapsis	27 184 000 m
Orbital eccentricity	0
Orbital inclination	0 °
Argument of periapsis	0 °
Longitude of the ascending node	0 °
Mean anomaly	3.14 rad (at 0s UT)
Sidereal orbital period	52 981 s
	2 d 2 h 43 m 0.9 s
Synodic orbital period	53 007.7 s
Orbital velocity	3 224 m/s
Longest time eclipsed	3 754 s
	Physical Characteristics
Equatorial radius	500 000 m
Equatorial circumference	3 141 593 m
Surface area	3.1415927×1012 m2
Mass	2.9397311×1022 kg
Standard gravitational parameter	1.9620000×1012 m3/s2
Density	56 144.728 kg/m3
Surface gravity	7.85 m/s2 (0.8 g)
Escape velocity	2 801.43 m/s
Sidereal rotation period	52 980.879 s
	2 d 2 h 43 m 0.9 s
Sidereal rotational velocity	59.297 m/s
Synchronous orbit	Outside sphere of influence
Sphere of influence	3 723 645.8 m
	Atmospheric Characteristics
Atmosphere present	Yes
Atmospheric pressure	60.7950 kPa
	0.6 atm
Atmospheric height	50 000 m
	6.0×10-7 atm
Temperaturemin	-74.15 °C 199 K
Temperaturemax	3.85 °C 277 K
Oxygen present	Yes
	Scientific multiplier
Surface	14
Splashed	12
Lower atmosphere	11
Upper atmosphere	10
Near space	9
Outer space	8
Recovery	8
	↑ 1.0 1.1 1.2 1.3 The distances are given from the body's center, not from the surface (unlike ingame) ;

Laythe is the innermost of the five natural satellites of Jool. Although mostly covered in seas, Laythe has numerous rocky, sandy islands. Laythe is tidally locked to Jool. Synchronous orbits around Laythe are not possible, as they would lie outside of its SOI, at a radius of 5,186,399 meters. A circular archipelago prominent in surface maps of the moon suggests that Laythe suffered a massive impact in its distant past.

Achieving a stable orbit around Laythe from sea level requires a delta-V of ≈2800 m/s.

Laythe has no real-world analogue. In the real-world Jupiter system, the moons Ganymede, Europa and Io form a group with an orbital resonance just like KSP's Tylo, Vall and Laythe. But while Tylo and Vall have a certain resemblance to their real-life counterparts, Laythe is very unlike Io, which is dry, volcanic, and only has a tenuous atmosphere. Instead, the presence of a liquid ocean, plus a dense atmosphere, makes Laythe more similar to the Saturnian moon Titan. Laythe also seems very similar to what happened to Europa in 2010: Odyssey Two.

Although Laythe has liquid water on its surface, its polar regions have temperatures below zero degrees Celsius even outside its ice caps. This means Laythe's oceans must contain another compound which reduces its freezing point, most likely ionic, such as salt. Surface samples indicate that much salt is present on Laythe's surface. Unlike that of Kerbin, the air cannot be breathed by Kerbals (according to EVA reports). It is therefore possible that there are also high concentrations of salt in the air, as well as on the surface, assuming that the salt is sodium chloride. The apparent toxicity of Laythe's atmosphere, despite being similar in composition to Kerbin's, may also be a reference to the film Avatar - the moon Pandora is very similar to Earth, but its atmosphere is too toxic for humans to inhale, and the moon also orbits a gas giant, like Laythe. Laythe may also be a reference to the planet Damogran from the radio/tv/book/movie series The Hitchhiker's Guide to the Galaxy, as they are almost, but not quite, entirely not unlike one another.

According to former developer NovaSilisko, Laythe was planned to have volcanic activity and high radiation levels in later versions, making it a much more hostile moon than in 1.4^[1]^[2]

In-game description

“

When Laythe was first discovered, it was not entered in the records because the scientist in charge thought he was looking at Kerbin.

Luckily this error was corrected when a plucky intern informed him that “telescopes don’t work that way”.

The intern was shortly afterwards “promoted” and moved to the experimental rocket testing program.''

— Kerbal Astronomical Society

”

Biomes

Laythe has 10 biomes. Laythe consists primarily of a huge ocean, called The Sagen Sea, with another ocean called the DeGrasse Sea and some small Peaks, Dunes and Shores biomes. It also has a Poles biome. The aforementioned seas are likely to be named after Neil DeGrasse Tyson and Carl Sagan, two famous physicists.

Biome list

Laythe In-game biome map as of 1.2

Poles
Shores
Dunes
Crescent Bay
The Sagen Sea
Crater Island
Shallows
Crater Bay
DeGrasse Sea
Peaks

Atmosphere

Temperature and pressure of Laythe's atmosphere as a function of altitude.

Laythe has an atmosphere thick enough and warm enough to support liquid water on its surface. The atmosphere has a mass of approximately 2.4×10¹⁶ kilograms, a sea level pressure of 60.795 kilopascals (0.6 atmospheres), and a depth of 50,000 meters. Compared to the atmosphere of Kerbin, Laythe's atmosphere has 1/2 the mass and 3/5^ths the surface pressure. The sea level pressure on Laythe is equivalent to that at an altitude of 3,287 m on Kerbin. The atmosphere contains oxygen and can support combustion; however, it is unbreathable by Kerbals. Laythe is the only moon in the game that has an atmosphere.

The average molecular weight of Laythe air is 28.9644 g/mol, and its adiabatic index is 1.40. These values suggest a compostion very similar to Kerbin, and to Earth — likely nitrogen and oxygen.

Like all other atmospheres in the game, Laythe's atmosphere fades exponentially as altitude increases. The scale height varies with altitude, which is a change from pre-1.0 versions of the game. The pressure-altitude profile is globally constant and independent of temperature. The following table gives the atmospheric pressure at various altitudes above sea level.

Altitude (m)	Pressure (Pa)	Pressure (atm)
0	60 795	0.600
2 500	47 153	0.465
5 000	34 495	0.340
7 500	24 914	0.246
10 000	17 786	0.176
15 000	9 351	0.092
20 000	4 782	0.047
25 000	2 671	0.026
30 000	1 507	0.015
40 000	363.5	0.004
50 000	0	0.000

The variation of temperature with height suggests the presence of an earthlike troposphere, stratosphere and mesosphere. The warm surface temperatures rapidly decrease as the alitude increases to 5 km. The stratospheric region, where temperature rises as altitude increases, spans the region between the altitudes of 10 km and 22 km.

Air temperatures vary with latitude and time of day. At the equator, sea level temperatures vary between a nighttime low of 9 °C and a daytime high of 15 °C. Mid-latitudes are only slightly cooler than the equatorial zone — at latitudes below 63°, the sea level temperature never drops below 0 °C. At the poles, the temperature varies between -26 °C and -24 °C. The globally averaged sea level temperature is approximately 9 °C. Since Laythe has no axial tilt, there are no seasonal temperature variations.

Laythe's surface temperatures are warmer than would be expected based on its distance from the sun. This suggests the possibility that Laythe generates its own heat, likely tidal heating.

Atmospheric flight

The thickness of Laythe's atmosphere makes it suitable for aerobraking and the use of parachutes.

With proper aerobraking near Laythe and Jool, reaching Laythe may require the least Δv of all of Jool's moons. Another way is to approach Laythe directly, utilizing proper timing and making orbital adjustments on the way to Jool. Laythe's orbital period makes it an easy target to time and will have required less Δv on arrival (only 2000 m/s). As such, aerobraking on Laythe is less extreme than on Jool.

Landing on higher points of Laythe's surface has to be done with the help of retro-burns, as parachutes alone will not suffice to sufficiently lower a craft's velocity for landing.

Jet engines work in Laythe's atmosphere due to the presence of oxygen. However, the air-intake efficiency is lower there.

Oxygen

As previously mentioned, Laythe's atmosphere contains oxygen enabling jet engines to function. Even though there is a lower concentration of oxygen than on Kerbin, plus an unknown toxic trace gas, most likely ozone, this oxygen almost surely has to be generated somewhere on Laythe. Molecular oxygen is extremely unstable compared to other atmospheric gases, and is even capable of reacting with itself to form ozone under certain conditions. Because of this unstable molecular oxygen must constantly be replaced for it to remain in any meaningful quantity in an atmosphere. This fact, combined with Laythe's extremely high concentration of liquid water, make it tempting to declare the presence of life on the moon. While it is possible that this is the case, it is also possible that the moon has a self-sustaining chemical process that constantly replenishes its oxygen reserves.

Science

Laythe is the most science-rich body in the Joolian moon system. Even though Tylo has a slightly higher science multiplier for both surface and orbit, Laythe's atmosphere and oceans allow a lot more experiments to be performed, which means the total science output is higher.

Reference frames

Time warp	Minimum Altitude
1×	Any
5×	50 000 m (above the atmosphere)
10×	50 000 m (above the atmosphere)
50×	60 000 m
100×	120 000 m
1 000×	240 000 m
10 000×	480 000 m
100 000×	600 000 m

Gallery

A large user-created probe in low orbit around Laythe.
A probe on the surface of Laythe.
A topographic map of Laythe made with ISA MapSat.
A grayscale bump map normalized at sea level.
A color map of Laythe
Vall as seen on Laythe
Tylo as seen on Laythe
Bop as seen on Laythe
Laythe transfer plan
A topographic height map of Laythe as at Version 0.18.2 made with the ISA MapSat plugin
Laythe's northern ice cap, with the Sun, Vall, and Tylo.
User-created jet flying in Laythe's atmosphere.
User-created jet space plane on re-entry to Laythe.
A direct approach to Laythe.
A modular, mobile base being set up at Laythe
Laythe passing Jool making them look the same size.