Planetology and the Worlds of Space:1889

When Edison returned from his flight to Mars in 1870, the field of astronomy was changed forever. Suddenly, objects that once could only be seen through a telescope could be visited first-hand. Planetology became distinct as a field of astronomy dealing with the characteristics of solid bodies within the solar system. Since 1870, planetologists have noted a variety of unexpected characteristics of planets through observing them first-hand.

Gravity Dilation

A number of planets show unexpected surface gravity compared with what we know about the planets from observation from Earth. For example, Mars exhibits a surface gravity of 0.9 G when its mass only justifies a pull of 0.4 G. Planetologists are at present baffled by this phenomenon. Tests performed on Mars show that all Gravitational attraction between bodies (not just attraction to Mars) is affected by this phenomena, roughly doubling the mutual atraction between masses. This effect extends several miles above the surface, but seems to dwindle quickly as the atmosphere thins, so once one is in space the normal gravitational effect occurs.

Venus also exhibits a similar, though less pronounced effect; Venus ought to have a surface gravity of 0.91 G and instead has a gravity of virtually 1.0 G. Luna exhibits a normal surface gravity but once one delves within the world, the local gravity increases gradually to almost 0.5 G.

Scientists are still baffled as to the origin of this effect, but a number of theories exist. One theory is that local atmosphere has a magnifying effect on gravitation, and that the constants of gravity need to be recalculated to take into effect what gravity dilation must exist on Earth. Since the function of the Ether is affected adversely by atmosphere it is theorized that gravity dilation may be connected and that gravity is an etheric force.

Another theory is that some quirk of chemistry causes planets with a particular composition to cause an "etheric gravity generator," a natural chemical that interacts with a local magnetic field to create a second "layer" of gravity generated by this. Mars' effect is so pronounced because the chemicals which are needed are also the same chemicals that allow liftwood to have it's lifting properties; since these chemicals are present throughout the planet this effect is generated.

A compromise theory is that the etheric effect in question "energizes" the atmosphere of the planet causing the effect to permeate the atmosphere. In the end, though, all these theories are just wild speculation.

The ultimiate implication, however, is that smaller worlds throughout the solar system might have surface gravities much higher than their small sizes would suggest.

Thermal Moderation

Another surprising detail about the explored planets is their surprising temperature ranges. Scientists expected that Mars would be much colder than it is, and Venus much hotter. Though Venus is hotter than Earth, and Mars cooler, the differences are smaller than expected by at least a factor of 10! Some other system of explaining weather besides strict solar energy had to be devised that dealt with this phenomena.

Geothermal heat was one of the most obvious explanations, and planetologists have suggested that the force that generates planetary magnetic fields also generates heat; rather than simply bleeding off existing heat planets actually create heat in their interiors. The mechanism for such a "planetary furnace" are as yet unknown. Other theories exist as well that suggest that heat is carried by the solar wind, or that the ether exhibits heat conducting properties that speed the process of heat radiation into the outer solar system.

If such a "planetary furnace" actually exists, the large outer planets are likely to be emitting a fair amount of heat, warming the smaller bodies nearby, who might also have their own "furnaces". Planetologists now expect that some of the moons of Jupiter and perhaps Saturn might actually be habitable. Such suggestions continue to prompt a renewed increase in interest in exploring the outer solar system.


Planetologists have started to catalogue the planets in new ways now that real exploration of the planets has become feasible. Planetologists have noticed that gradations seem to exist in the sizes of planets and moons in the solar system, with many objects having similar sizes and then there being "gaps" before a smaller size is seen.

A classification system sprang into being virtually simultaneously from two different sources. The Royal Astronomical Society proposed a hierarchical system of numbered planetary classes, with 1 being the largest and 9 being the smallest. The American Society of Astronomers published their own classification system in collaboration with the French, which used letters to classify planets instead of numbers, though the groups were the same. The letters were supposed to provide some descriptive quality rather than the simple numric system. Each larger class is betwen 2 and 2.5 times larger than the previous smaller class. The demarcation points are arbitrary but were originially meant to parallel the system of magnitude used for classifying stars.

British Class American Class Planetary Diameter Examples
Type 1
"J" Class
50,000 - 125,000 miles Jupiter (89,400)
Saturn (75,700)
Type 2
"G" Class
20,000 - 50,000 miles Uranus (32,000)
Neptune (31,000)
Type 3
"H" Class
(Heavy, or "Hypothetical")
10,000 - 20,000 miles (none in solar system)
Type 4
"T" Class
5,000 - 10,000 miles Earth (7927)
Venus (7526)
Type 5
"M" Class
2500 - 5000 miles Mars (4200)
Ganymede (3288)
Titan (3220)
Mercury (3030)
Callisto (3000)
Type 6
"L" Class
2500 - 1000 miles Io (2270)
Luna (2160)
Europa (1960)
Triton (1700)
Pluto (1400)
Type 7
"P" Class
1000 - 400 miles
Osiris* (1000)
Sedna (1000)
Titania (980)
Rhea (956)
Oberon (950)
Iapteus (910)
Quaoar (810)
Charon (733)
Umbriel (731)
Ariel (725)
Dione (700)
Tethys (662)
Ixion (660)
Varuna (595)
Ceres (582)
Demogorgon* (556)
Elohim* (550)
Brahman* (540)
Kukulcan* (525)
Pele* (525)
Thanatos* (510)
Ahura Mazda* (495)
Arawn* (460)
Djamu* (460)
Huracan* (460)
Nergal* (445)
Ptah* (445)
Marduk* (445)
Tiamat* (445)
Chaos (428)

(* represents Kuiper Belt objects which
have not yet received an official
designation as of the time of this article.
See The Outer Void for details)
Type 8
"Q" Class
400 - 160 miles
Pallas (334)
Vesta (325)
Enceladus (322)
Miranda (295)
Hygiea (270)
Proteus (261)
Mimas (245)
Euphrosyne (230)
Interamnia (220)
Nereid (212)
Davida (210)
Chariklo (200)
Europus (195)
Cybele (194)
Hyperion (180)
Patienta (173)
Eunomia (170)
Juno (160)

(Plus over a hundred Kuiper Belt objects)
Type 9
"A" Class
less than 160 miles (everything else - tens of thousands of objects)

Theorists maintain that a hypothetical Type-3, or "H"-class world might exist elsewhere in the universe, though detractors suggest that such a planet might not be stable and that it is foolish to classify a type of world when no examples exist.

It is also possible in theory to have a Type-0 or "S"-class (superjovian) world, but again no examples actually exist to demonstrate this.

Some detractors of this system suggest that the Type-9 or "A"-class objects should be further subdivided, adding a Type-10 or "A2"-class of objects smaller than 64 miles in diameter. Others argue that the division between Type-9 or "A"-class and Type-8 or "Q"-class is unnecessary as these two world types show largely the same characteristics. Navigators seem happy with the current system, however, so for the time being it is unlikely to change.


The Planetary classification system not only divides the bodies of the solar system into categories, but also makes predictions about unexplored bodies based on experience. The following is a list of the presumed characteristics of each class of planet.

Type 0
"S" Class
The Superjovian planet is a hypothetical planetary class as no planets in this category have so far been observed. Scientists assume that Superjovian planets not only have the powerful magnetic fields and thermal energy of Jovian planets, but actually generate enough heat and energy that, while not stars, they will yet emit light in the red end of the spectrum. While very dim compared to a star such a world is still generating power and could be considered a star that "didn't quite make it."
Type 1
"J" Class
The Jovian planet class is based on Jupiter and Saturn and represents the larger type of gas giant world. Jovian planets are extremely heavy and have enourmous surface pressures and temperatures, though it is by no means proven that they even have a surface at all. Their interiors are probably mostly Hydrogen and Helium, but the gravity of these planets makes it impossible for these lighter gases to escape. Jovian planets also generate extreme amounts of electrical energy in their magnetic fields and also emit a substantial mount of heat.
Type 2
"G" Class
The Giant planet class is based on Uranus and Neptune and displays similar characteristics as a Jovian planet, though the amount of heat and magnetism generated is much less (though still substantial). Giant planets have strong gravitational attraction, though their density is much less, so the gravity that would be observed at a hypothetical surface (since, like Jovians, it is not known if they have a surface) is actually similar to that of Earth's, assuming no gravity dilation. There may also be breathable layers in the atmosphere of these worlds, though this is speculation. Some planetologists argue that Saturn exhibits more of these qualities and properly belongs in this category, despite its size.
Type 3
"H" Class
The Heavy planet is a hypothetical class that represents a large, Earth-like planet, but with a very thick atmosphere. Gravity on such a world would be higher than Earth's, but not extremely so as the radius of such a world places the inhabitant further from the center of gravity. The high pressure of such an atmosphere is what might pose a problem on such a world, though it is not known exactly what effects this might have on life. Also, the thick atmosphere and large world suggests that such a planet would be warmer than other worlds in the same conditions.
Type 4
"T" Class
The Terran planet is, as the name suggests, Earth-like and posesses a thick atmosphere magnetic field, and abundant surface water. Conditions on the surface of a terran planet tend to make it an ideal habitat for living things.
Type 5
"M" Class
The Martian planet is smaller than the Terran world, and correspondingly has less free water on the surface, a thinner atmosphere, and lower gravity. However, since all observed M-class worlds sustain life, it is believed that the three other M-class worlds in the solar system (Ganymede, Callisto, and Titan) will also be habitable.
Type 6
"L" Class
The Lunar world is comparable in size to Earth's Moon, and since the Moon has no atmosphere, it seems less likely that L-class worlds will posess an atmosphere. However, since there is some evidence that Luna once posessed an atmosphere, planetologists give the solar system's three other known L-class worlds (Io, Europa, and Triton) a good chance of having an atmosphere. However, such an atmosphere would likely be thinner and the planet might not have very much free water.
Type 7
"P" Class
The Planetoid class is quite small (about 1/10th the diameter of Earth) and the asteroid Ceres is among this class. However, the planetoid is large enough that local gravity is still enough to make the world conform to a spherical shape. Planetologists think that this may be an indication that some chance of an atmosphere and life exists for such worlds, though odds may be against it. Such worlds do not have intrisic magnetic fields of any real strength and are not likely to have much internal heat. Objects in P-class or below are never considered "planets."
Type 8
"Q" Class
The Quasi-Planetoid represents a borderline between Asteroids and Planetoids. The Quasi-Planetoid may sometimes have enough gravity to cause it to take a spherical shape, but sometimes not. They are unlikely to have atmospheres (though it is not impossible), though if the object is round there is a better chance than otherwise. Most planetoids will simply show the traits of larger asteroids.
Type 9
"A" Class
The Asteroid is always irregular in shape and never has an atmosphere. They are generally considered to be just large rocks floating in space. However, their small size and low gravity makes it potentially easy to mine ores from them. There are thousands of such objects in the solar system.