This is an expansion of the material mentioned on:
You should read that first before continuing with this page. On that page we mentioned these 5 processes that affect the surface attributes of the earth and we need to understand them in more detail.
These processes have been placed into five groups:
- Erosion, weathering and sedimentation.
- Impact cratering.
- Surface fracturing and distortion.
- Mountain-building, plate tectonics and continental drift.
To what extent are the geological processes observed on other planets and their moons similar to what has been observed on Earth? Unmanned spacecraft have been placed on the surface of Mars and Venus; while other vehicles have flown past Mercury and the moons of Jupiter and Saturn. We do have some information available to formulate a hypothetical answer to this question. It is still speculation as to how it applies to actual processes on earth, but some generalities can be assumed.
Erosion by both wind and water (or something like water) is evident on Mars. We know this from satellite imaging and just about any Hollywood movies having to with Mars which endangers the poor earthlings that have had the misfortune to land there (https://en.wikipedia.org/wiki/List_of_films_set_on_Mars) . Weathering by bombardment and temperature extremes seems to be widespread.
From decades of observing Mars, scientists know there is a seasonal pattern to the largest Martian dust-storm events. Neither of the two current NASA Lander’s on Mars (Opportunity and Curiosity) have experienced a sand storm, although Curiosity did detect a drop in atmospheric pressure during one that was a couple hundred kilometers away. Weathering of observable features by bombardment of asteroids and temperature extremes seems to be widespread.
Impact cratering has been modeled in experiments involving detonating an explosion at ground level, so that scientists are quite confident that they know at least what energy of impact is required to produce a certain sized crater. Impact cratering is of course evident on the Moon and most other planets and their moons. Venus and the Earth have comparatively less impact cratering, which would be expected on account of their dense atmospheres. (It is of interest to note, however, that geologists are now recognizing evidence of more impact craters on the Earth’s surface than previously.) Sometimes cratering is unevenly distributed, suggesting that later volcanic action or melting has obliterated earlier impact craters—for example, on the Saturnine moon Enceladus.
Approximately 200-per-year space rock impact rate for Mars was based on a portion of the 248 new Martian craters that have been identified in the past decade using images from the Mars Reconnaissance Orbiter, a NASA spacecraft that has been circling the Red Planet since 2006.2 Now I may be wrong (but I didn’t learn math under Common Core), but its been almost 10 years the satellite has been up there and 248 Martian craters divided by 10 years is only 24.8 craters per year. But what do I know.
(The belief is the shiny one is indication of a fairly new impact crater since it isn’t covered with red sand as much as the others and shows sharp edges. Of course then the real small one beside it and under the other one must have hit sometime in between them wouldn’t you think?)
Most of our knowledge about how landforms have evolved on Mars is based upon interpretation of images taken by the Mariner and Viking Orbiters and the Viking and Pathfinder Landers. Many landforms on Mars remain enigmatic — the processes, environments, and constituent materials involved in their formation are either totally uncertain or subject to a variety of interpretations. This is particularly true for channels and valleys on Mars, as well as the extensive heavily cratered terrain, which has a morphology very different from cratered landscapes of airless bodies such as the Moon.
To understand how surface processes have modified Martian landscapes we can only rely upon interpretation of images from orbiters and lenders, and, as discussed here, computer simulation of erosion.
The Martian facts are just that, speculation at best. Some good speculation I will admit, but even with close orbiters and Landers just speculation at this point.
Volcanism has been identified on most of the solar system’s planets and their moons. The largest volcano known is on Mars: the 25km high Olympus Mons.4 What appear to be lava flows from volcanic outpourings are observed in many other places; notably the Moon and Mercury. Evidence strongly suggesting active volcanoes have even been found on Io, one of Jupiter’s moons.5
Surface fracturing has been observed on Mercury in the Caloris Basin. This is possibly due to shock from an impact, or maybe the result of solidification processes after melting. Extensive surface fracturing is also found on Mars, particularly in the Tharsis region. This has been correlated with stresses resulting from surface gravity and topography.
In summary then, the first four categories are widely observed within the universe that we are able to perceive. But mountain-building processes and plate tectonics appear to be strangely absent. On Venus ‘The tectonic motion of large crustal plates appears not to have played the dominant role in altering the surface that tectonic motion has on the Earth’. While for Mars ‘This tectonic framework [of Earth] provides a striking contrast to that on Mars, where there are no plate tectonics’, and ‘Whatever the origin of Tharsis—be it deep seated uplift or long lasting volcanism—the nature of Martian tectonics is still vertical, rather than the horizontal varieties seen on Earth’. Indeed, the Earth differs from all the other terrestrial planets in that it alone has folded mountain chains, and platform deposits—“The Earth terrain map appears remarkably different than maps of the other terrestrial planets”.
This conclusion, derived from comparative study of geological processes on the Earth, the other planets of the solar system and their moons, that there are some geological processes unique to the Earth, is at first startling, and then somewhat disturbing. If we have found what is possible on all the other planetary bodies, we can perhaps conclude that what is left out and therefore unique to the Earth must be due to some as yet unknown factor operative on the Earth. There is no doubt that mountain-building has taken place during the Earth’s history, but if the plate tectonics and continental drift ideas have to be rejected, then we are at a loss to know by what forces do mountain chains form by folding of the Earth’s crustal strata?
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1 Masursky, H., Mars. In: Beatty, J.K. (ed.), The New Solar System, Cambridge University Press, pp. 86–87, 1981.