One of the main objectives of Nature Astronomy is to foster the development of comparative planetology studies, including exoplanets. Page 1. Comparative Planetology of the Terrestrial Planets. Page 2. Basic Characteristics. • Inside the Frost Line. • Smaller than the Gas Giants. • Rocky surfaces. Comparative Planetology. ▫ Overview. ▫ The Earth as a Template. ▫ Understanding the governing parameters. ▫ The Outer Planets. ▫ Jupiter, Saturn, Neptune.


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Comparative Planetology | ScienceDirect

Background[ edit ] The term "comparative planetology" was coined by George Gamowwho reasoned that to fully understand our own planet, we must study others. Poldervaart focused on the Moon, stating "An adequate picture of this original planet and its development to the present earth is of great significance, is in fact the ultimate goal of geology as the science leading to knowledge and understanding of earth's history.

Volcanism Volcanism on Earth is largely lava -based. Other terrestrial planets comparative planetology volcanic features assumed to be lava-based, evaluated in the context of analogues readily studied on Earth.

For example, Jupiter's moon Io displays extant volcanismincluding lava flows.

Comparative planetary science - Wikipedia

These flows were initially inferred to be composed mostly of various forms of molten elemental sulfurbased on analysis of imaging done by the Voyager probes. Surfaces in the comparative planetology regions show polygonal morphologiesalso seen on Earth.

These domes lack comparative planetology known Earth analogue. They do bear some morphological resemblance to terrestrial rhyolite-dacite lava domesalthough the pancake domes are much flatter and uniformly round in nature.

Cryovolcanism is studied through laboratory experiments, comparative planetology and numerical modeling, and by cross-comparison to other examples in the field.

Comparative Planetology

Examples of bodies with cryovolcanic features include cometssome asteroids and CentaursMarsEuropaEnceladusTritonand possibly TitanCeresPlutoand Eris. The trace comparative planetology of Europa's ice are currently postulated to contain sulfur.


Assumed to have experienced little or no heating, these materials may contain or be samples representing the early Solar System, which have since been erased from Earth or any other large body.

Some extrasolar planets are covered entirely in lava oceansand some are tidally locked planets, whose star-facing hemisphere is entirely lava.

Impact crater The craters observed on the Moon were once assumed to be volcanic. Earth, by comparison, did not show a similar crater count, nor a high frequency of large meteor eventswhich would be comparative planetology as two nearby bodies should experience similar impact rates. Eventually this volcanism model was overturned, as numerous Earth craters demonstrated by e.

Craters formed by larger and larger ordnance also served as models.


The Moon, on the other hand, shows no atmosphere or hydrosphere, and could thus accumulate and preserve impact craters over billions of years despite a low impact rate at any one time.

In addition, more searches by more groups with better equipment highlighted the great number of asteroids, presumed to have been even more numerous in earlier Solar System periods. This is particularly credible if nearby comparative planetology or bodies show heavier cratering.


Young surfaces, in comparative planetology, indicate atmospheric, tectonic or volcanic, or hydrological processing on large bodies and comets, or dust redistribution or a relatively recent formation on asteroids i.

However, the Late Heavy Bombardment as currently proposed has some issues and is not completely accepted.

Comparative planetary science

Planetary differentiation As comparative planetology large body, Earth can efficiently retain its internal heat from its initial formation plus decay of its radioisotopes over the long timescale of the Solar System.

It thus retains a molten coreand has differentiated - dense materials have sunk to the core, while comparative planetology materials float to form a crust. Other bodies, by comparison, may or may not have differentiated, based on their formation history, radioisotope content, further energy input via bombardment, distance from the Sun, size, etc.