Venus, Cloudy With A Chance of Life

Distance from Sun
0.72 x Earth
Volume
0.86 x Earth
Length of Day
243 Earth days
Length of Year
225 Earth days

Facts worth sharing

  • Venus, the second planet from our Sun, may have had oceans and been habitable to life before being transformed into an inhospitable wasteland.
  • By studying Venus, scientists learn how Earth-like planets change over time, and what conditions on Earth-sized planets orbiting other stars might be like.
  • Scientists have predicted that life could currently exist in Venus' upper atmosphere, where some regions have Earth-like temperatures and pressures.

Why study Venus?

Venus is the hottest planet in the solar system, even though Mercury is twice as close to the Sun and receives 4 times more solar energy. The reason? Venus’ thick, carbon dioxide atmosphere causes a runaway greenhouse effect. At the surface Venus has an atmosphere 50 times denser than Earth’s, and average surface temperatures of 470 degrees Celsius (878 degrees Fahrenheit)—hot enough to melt lead.

Venus is currently inhospitable, but it wasn’t always that way. Missions there have observed granite-like rocks that require abundant water to form. In the solar system's early days when the Sun was cooler, scientists think the planet may have had liquid water on the surface for 2 billion years—far longer than Mars, which had liquid water for a relatively shorter 300 million years. Water is the key to life as we know it, so did Venus once have life?

Scientists including Planetary Society co-founder Carl Sagan have predicted that life could currently exist in Venus' upper atmosphere, which has Earth-like temperatures and pressures roughly 50 kilometers (31 miles) above the planet's surface. There, mysterious dark patches absorb more than half the planet's solar energy. In 2020 scientists announced they had found phosphine, a chemical strongly associated with life, in Venus's clouds—though the existence of the signal is currently being reviewed.

We don't know how Venus transformed from a potentially habitable world to its current hellish state. By studying Venus, scientists learn how Earth-like planets evolve and what conditions exist on Earth-sized exoplanets. Venus also helps scientists model Earth’s climate, and serves as a cautionary tale on how dramatically a planet’s climate can change.

Global view of Venus from Magellan
Global view of Venus from Magellan Image: Mattias Malmer/NASA JPL

How we study Venus

Venus was the first planet to be visited by a spacecraft. In 1962, NASA’s Mariner 2 flew by the planet and discovered it was a hot world with no self-generated magnetic field. The Soviet Union became the world leader in early Venus exploration after that, sending multiple atmospheric probes and as many as ten landers to the planet. To this day, they remain the only nation to have landed spacecraft on the surface and transmitted both data and images back to Earth.

Due to thick clouds, it is impossible to see Venus’ surface without radar. NASA’s Magellan orbiter, launched in 1990, used radar to map Venus’ surface at the highest resolution to date. Magellan revealed that all of the planet’s impact craters are formed within the last 700 million years. This implies that Venus’ surface was completely reshaped by a worldwide volcanic event in its recent geologic past—but exactly what happened is still up for debate.

Magellan also found no sign of plate tectonics. On Earth, plate tectonics is a process in which sections of the planet’s outer crust glide over the mantle—the rocky inner layer above the core—allowing heat to escape through volcanism. Since we think Venus’s interior is similar to Earth's, the lack of plate tectonics means that volcanoes on Venus must work differently than on Earth.

The European Space Agency launched the Venus Express orbiter in 2006. By observing hotspots on the surface and changing sulfur dioxide levels in the atmosphere over 6 years, the spacecraft collected the best evidence yet of active volcanism on Venus. Venus Express also discovered granite-like rocks across the planet that require abundant liquid water to form, solidifying the idea of the planet having past oceans.

Japan’s Akatsuki spacecraft is the only probe currently orbiting Venus. It studies Venus’s atmosphere in frequencies of light that human eyes cannot see, which helps scientists paint a better picture of what’s happening above the planet’s surface. These images can be processed to create beautiful enhanced-color pictures of the planet.

Only 3 missions have visited Venus in the past 30 years, and many scientists feel new missions are long overdue. A spacecraft with a higher-resolution radar could help us solve the mystery of how Venus’s surface changed within the last billion years. Landers and atmospheric probes would analyze the extent that water may have existed on the surface, what the planet’s atmosphere was like, and how it changed into its present-day state.

India aims to launch a Venus orbiter called Shukrayaan in December 2024 equipped with a radar and infrared camera to map the surface. It will have a payload capacity of about 100 kilograms and study Venus for four years from a polar orbit of 200 x 600 kilometers. The spacecraft will carry both Indian and international science instruments. One, called VIRAL  (Venus Infrared Atmospheric Gases Linker), will be co-developed by the French and Russian space agencies.

In February 2020 NASA announced the selection of 4 mission concepts that are under consideration to fly as part of the agency’s low-cost Discovery program. Two are Venus missions:

  • DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging Plus) consists of an orbiter and an atmospheric descent probe. The probe would make high precision measurements of trace gases in Venus’ atmosphere, helping firmly determine how much water Venus’ oceans had and how long they existed.
  • VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) would have a radar instrument with up to 100 times higher resolution than Magellan. This would give scientists a better handle on Venus’ geology and evolution and also reveal why the planet lacks large-scale plate tectonics.
Venera 13's landing site
Venera 13's landing site A processed and colorized panorama from the Venera 13 lander, the third spacecraft to return images from the surface of Venus, on March 3, 1982. Data gaps were filled in by hand. Four Venera landers remain the only spacecraft to have returned photos from beneath Venus' obscuring cloud deck, two each in 1978 and 1982.Image: Brown University / Vernadsky Institute / Olivier de Goursac

How you can support Venus exploration

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Venus on Planetary Radio

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Acknowledgements: This page was initially written by Jatan Mehta in 2020 and is regularly revised and updated by Planetary Society staff writers.