Venus

 
Venus

Image Credit: NASA

Venus (also known as the Morning or Evening Star) is the second planet from the Sun. After the Moon, it is the brightest natural object in the night sky, and with temperatures that reach 870 degrees F (465 degrees C), it is the hottest world in our solar system.

Venus is one of the four solar terrestrial planets, meaning that, like the Earth, it is a rocky body. In size and mass, it is very similar to the Earth, and is often described as Earth’s “sister” or “twin”, but it has no natural satellite. The diameter of Venus is 12,092 km (only 650 km less than the Earth’s) and its mass is 81.5% of the Earth’s. The similarity in size and density between Venus and Earth suggests they share a similar internal structure: a core, mantle, and crust.

About 80% of the Venusian surface is covered by flat, smooth plains that are marred by thousands of volcanoes, ranging from about 0.8 to 240 kilometers wide, with lava flows carving long, winding canals up to more than 5,000 kilometers in length, longer than on any other planet. The sulfur in the atmosphere may indicate there is ongoing volcanic activity and even some recent eruptions.

Venus has two highland “continents”, one (Ishtar Terra) lying in the planet’s northern hemisphere and the other (Aphrodite Terra) just south of the equator. Its six mountainous regions include Maxwell Montes, which lies on Ishtar Terra. This 870 kilometers long mountain is the highest one on Venus, its peak is 11 km above its surface.

The planet has just about a thousand impact craters which are evenly distributed across its surface, demonstrating the surface is relatively young, approximately 300–600 million years old. These craters range from 3 km to 280 km in diameter.

Venus is covered with an opaque layer of highly reflective clouds of sulfuric acid, preventing visual observation of its surface. Strong 300 km/h winds at the cloud tops circle the planet about every four to five earth days. High in its atmosphere is an ozone layer, but it has a very weak magnetosphere.

The atmospheric pressure at the planet’s surface is 92 times that of the Earth and this extremely dense atmosphere consists mostly of carbon dioxide, with a small amount of nitrogen. Studies have suggested that billions of years ago, the atmosphere of Venus was much more like Earth’s than it is now, and that it previously possessed oceans, but a runaway greenhouse effect was caused by the evaporation of that original water, which generated a critical level of greenhouse gases in its atmosphere.

Although the surface conditions on the planet are no longer hospitable to any Earthlike life that may have formed prior to this event, the possibility that a habitable niche still exists in the lower and middle cloud layers of Venus can not yet be excluded.

The Venusian year — the time it takes to orbit the sun — is about 224.7 Earth days long. Its rotation is by far the slowest of any of the major planets, namely 243 Earth days, which normally would mean that days on Venus would be longer than years. However, because of Venus’ curious retrograde rotation, the time from one sunrise to the next is only about 117 Earth days long.

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