Extremely bright in the early evening and morning sky, Venus is a captivating target and enigmatic celestial object.

The Planet

Of all the planets within the Solar System, none are as similar to the Earth, in physical features, as Venus is. Venus is just under 650km narrower than the Earth, and has a surface gravity that is approximately 90% of Earth’s. Both planets are close to the Sun, with Earth at 150 million km and Venus at 108 million kilometres. Venus also retains a thick permanent atmosphere that can be observed through a sufficiently powerful backyard telescope. However, the similarities end here. Unlike the Earth, Venus has a retrograde rotation, meaning sunrises occur in the west, and set in the east. Venus rotates extremely slowly, with a single day on Venus taking as long as 243 Earth days. Comparing this day length to the orbital period of Venus, 224 Earth days, means that a day on Venus lasts longer than an entire year.

A comparison of a radar image of the surface of Venus and the Earth. Image source: NASA

Venus also appears to have an unusually young surface, with very few impact craters. This suggests that Venus is a geologically active planet, with regular volcanic eruptions. This is also supported by spikes in the amount of sulphur dioxide, a chemical released in volcanic eruptions, over time and, in one instance, a temporary “hot-spot” on the surface that persisted for a few Earth days. Despite the volcanism, Venus doesn’t appear to have active plate tectonics, meaning that once significant pressure builds in Venus’ mantle, the crust splits and the face of the planet is covered in lava. This lava eventually solidifies and ‘resets’ the face of the planet.

An ultraviolet image of Venusian clouds. Image source: JAXA (CC BY 2.0)

The Atmosphere

The Venusian atmosphere is just as interesting and dynamic as the planet’s surface. At 92 times the mass of Earth’s atmosphere, the sea-level atmospheric pressure of Venus is comparable to that experienced at a depth of 1km below sea-level here on Earth. The atmosphere is composed of 96% carbon dioxide, which has turned Venus into a planet-sized greenhouse. A runaway greenhouse effect has caused the planet to heat to such an extent that the average surface temperature of Venus exceeds 450 °C, making Venus the hottest planet in the Solar System.

Photo of the surface of Venus, as imaged by the Soviet Venera 13 Lander

The Missions

Venus has a rich history of space exploration, starting with the Soviet Venera 1 spacecraft being the first craft launched to another planet despite contact being lost en route. The following year, in 1962, NASA’s Mariner 2 became the first successful interplanetary mission when it flew by Venus. Venus was also the first planet to be successfully landed on by a robotic spacecraft, having been visited by the Soviet Venera 7 craft in 1970.

In the decades since, Venus has been visited by 42 different spacecraft with 6 more craft due to visit the second planet from the Sun in the next 10-20 years.

How do I see Venus?

At the time of writing, Venus is visible in the early evening just after sunset as extraordinarily bright star low to the west. When viewed through a telescope, Venus will appear in a gibbous phase, similar to an almost full Moon. 

Riley Johnston

Riley is an experienced astronomy guide who has been working within the astronomy community for several years. He is incredibly passionate about the night sky and holds a Bachelor’s Degree in Science, Math and Education.

Riley Johnston


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