Why are Earth and Mars the same

Venus: twin planet of the earth


Venus is our inner neighbor in space in the solar system. If you relate it to the closest point, it is just 40 million kilometers from Earth. Mars, our outer neighbor, is at least 56 million kilometers away.
Venus resembles the earth in the main parameters: size, mass, density and internal structure almost match. Gravity is also almost similar: an earthly being weighing 80 kilograms would weigh 72 kilograms on the planet of love. Physically, Venus can therefore also be represented as Earth's smaller twin sister.

The length of the year is easy to understand. Venus orbits the sun in just under 225 days at a distance of 108 million kilometers. The earth needs 365 days for the same process at a distance of 150 million kilometers.
With the length of the day it gets more complicated. While the earth rotates around its own axis once every 24 hours, Venus rotates extremely slowly. 243 earth days pass before Venus has rotated once around its axis. During this time, more than a Venus year has passed. So we have the paradox that a Venus year (225 days) is shorter than a Venus day (243 days).

On its seven-month journey around the Sun, Venus approaches our blue home planet to within 40 million kilometers. Nevertheless, the differences between the two planets seem to be greater than between Earth and Mars, which is twice as far away.

The planetologists assume that the four inner rock planets of the solar system - Mercury, Venus, Earth and Mars - have a very similar history of formation. They were formed from the dust of that interstellar cloud from which the sun and then the planets emerged 4.6 billion years ago. In the course of time, the dust particles merged into ever larger clumps, condensed under the increase of their own gravity and gradually agglomerated to form larger celestial bodies, today's planets. Therefore, the geological structure of Venus should essentially resemble that of the earth. In any case, Venus also has a dense iron-nickel core that is surrounded by a jacket. There is a thin crust on top. The atmosphere of Venus consists mainly of carbon dioxide. The clouds can also contain droplets of sulfuric acid.

Fiery giants: ripe for the Guinness Book of Records

When evaluating the radar images, the researchers found neither oceans nor lakes. There does not seem to be any water in liquid form on the surface of Venus. From the landed Soviet Wenera probes, the soil is known to be bone dry.

In contrast, there is an abundance of fiery things: thousands of volcanoes cover the planet. These include giants, such as the 8000 meter high Maat Mons at the equator of Venus or the Theia Mons with a base diameter of 700 kilometers. This corresponds roughly to the distance from Hamburg to Munich. Or in other words: The Theia Mons volcano would take up almost the entire area of ​​Germany.

In general, the researchers found astonishing dimensions in the shield volcanoes. Almost 150 of them are each several kilometers high and have a base diameter of well over 100 kilometers. Over 300 volcanic domes (bulges) and calderas (depressions) with a diameter of up to 100 kilometers characterize the surface. And gullies up to 7000 kilometers long show that the lava was apparently very thin and flowed for a long time.

Gigantic lava masses have flooded large areas of the surface of Venus. Unusual volcano-tectonic forms can be found everywhere. For example, in the Eistla region to the north of the Venus equator, there are two volcanic domes over 50 kilometers in size, which arch about 1000 meters above the surrounding plain. Due to their unusual appearance, which is so far unique in the solar system, the planetologists refer to these volcanoes as pancake domes.

The question remains: is Venus still active today? The space probe's temporal insight was too short to give a clear answer to the question. It definitely seems to be seething on the surface. It is still unclear to what extent the volcanoes are still active. Fluctuating concentrations of sulfur dioxide indicate at least active volcanism. The ESA space probe Venus Express is supposed to answer this question.

Unknown Driving Forces: Is Venus Inflating?

Strange scars, which indicate the expansion of what is happening inside the planet, can be found by the hundreds on the surface. They could be an indication that hot magma rises vertically from the mantle of Venus, expands the surface, cools it down again and then sinks. This mechanism could - in a much larger dimension - also have played an important role in the planetary evolution of Venus. It is unclear how the current rigid surface was formed.

Measured against the total age of Venus of 4.6 billion years, the current planetary skin is geologically very young with an age of 500 to 800 million years. Older material is not found on the planet. Since the surface is not renewed by plate tectonics, another - as yet unknown - geological process must be responsible for the fundamental planetary changes. There are many indications that a globally effective process completely reshaped the face of the planet around 600 million years ago.

Perhaps there are periods of global volcanism in the history of Venus? This would inflate the planet in such a way that young, hot volcanic material comes to the surface, while the old, pending material is pulled into the depths. Then the new surface cools, contracts and falls off in some places.
The Venus Express mission is to answer whether such a mechanism actually existed and whether it still exists.

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