On Earth, most volcanoes form along the boundaries between tectonic plates. Like volcanoes, impact craters are distributed nearly randomly on its surface. Thus, these craters likely formed after most of the volcanic activity on the surface died down. There are also not very many impact craters, which suggests a youthful surface on average, to million years old , unlike the ancient surfaces of the Moon, Mercury, and Mars. What could make a young surface, covered with volcanoes and pristine craters?
Other scientists disagree. Therefore, scientists think such circulation inside Venus has developed differently from what happens inside the Earth. If the entirety of the Venusian surface was replaced by a worldwide volcanic event, how long did it take?
Was it dramatic and catastrophic, completed in a hundred thousand years or less, or could it have been an incremental, yet still globally effective process stretched over more than a hundred million years? The planetary geology community does not agree on this point. Different scientists have proposed different volcanic resurfacing models, all of them consistent with the young impact cratering record but disparate in their approach to explaining the evolution of the planet.
For scientists discussing Venusian history, there are two extreme points of view: catastrophic and steady-state. These terms refer to the primary difference between the two models, which is how long the resurfacing of Venus actually took. The catastrophic resurfacing model suggests that planetary resurfacing on Venus occurred through infrequent, planet-wide volcanic events, large enough to bury all earlier material. In other words, resurfacing was a near-instantaneous change to Venus relative to the slow flow of geologic time.
Steady-state, on the other hand, implies numerous smaller, discrete processes, stretched out across time. For Venus, the steady-state model posits more frequent resurfacing episodes, more similar to the pace of volcanism on Earth, that obliterate older craters at the local scale over much longer timescales. If the location and timing of the volcanism work out, a slower pace might still yield a young age for the surface overall.
Simply, no. If it was a collision that caused Venus to rotate clockwise opposite of the Earth , this probably happened long ago at the same time that the planets were still forming and that a Mars-sized object hit the Earth and formed the Moon.
It is likely, based on what we see now, that what happened on Venus million years ago was due to a turning over of the surface. Without the water to allow for plate tectonics, it is harder for Venus to get rid of its internal heat.
So, the mantle gets hotter and eventual melts the crust, forming a whole new surface. This process probably takes about million years and is probably when most of the volcanoes on Venus formed—very little erosion to weather them away.
We do not think so. It might have been the other way around: early Venus was similar to the early Earth before a runaway greenhouse turned Venus into what it is today. How long is a year on Mercury? How long is a day on Mercury? How fast does Mercury orbit the Sun?
How close is Mercury to the Sun? How strong is the gravity on Mercury? How small is Mercury compared to Earth? Lakshmi is a Hindu goddess of prosperity. Convection currents of molten material in the mantle of Venus push and stretch the crust.
Such forces are called tectonic , and the geological features that result from these forces are called tectonic features. In a few places, the crust has even torn apart to generate rift valleys. The circular features associated with coronae are tectonic ridges and cracks, and most of the mountains of Venus also owe their existence to tectonic forces. The Ishtar continent, which has the highest elevations on Venus, is the most dramatic product of these tectonic forces.
Both are the product of compression of the crust, and both are maintained by the continuing forces of mantle convection. The successful Venera landers of the s found themselves on an extraordinarily inhospitable planet, with a surface pressure of 90 bars and a temperature hot enough to melt lead and zinc. Despite these unpleasant conditions, the spacecraft were able to photograph their surroundings and collect surface samples for chemical analysis before their instruments gave out.
The diffuse sunlight striking the surface was tinted red by the clouds, and the illumination level was equivalent to a heavy overcast on Earth. The probes found that the rock in the landing areas is igneous, primarily basalts.
Examples of the Venera photographs are shown in Figure 5. Each picture shows a flat, desolate landscape with a variety of rocks, some of which may be ejecta from impacts.
Other areas show flat, layered lava flows. There have been no further landings on Venus since the s. Figure 5. Surface of Venus: These views of the surface of Venus are from the Venera 13 spacecraft.
Everything is orange because the thick atmosphere of Venus absorbs the bluer colors of light. The horizon is visible in the upper corner of each image. Venus has been mapped by radar, especially with the Magellan spacecraft. The planet has been modified by widespread tectonics driven by mantle convection, forming complex patterns of ridges and cracks and building high continental regions such as Ishtar.
The surface is extraordinarily inhospitable, with pressure of 90 bars and temperature of K, but several Russian Venera landers investigated it successfully. Skip to main content. Earthlike Planets: Venus and Mars. Search for:. The Geology of Venus Learning Objectives By the end of this section, you will be able to: Describe the general features of the surface of Venus Explain what the study of craters on Venus tells us about the age of its surface Compare tectonic activity and volcanoes on Venus with those of Earth Explain why the surface of Venus is inhospitable to human life.
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