Why will NASA return to explore Venus after 40 years?

Venus can be seen as a small black dot.


For decades, exploration of our solar system left one of our neighboring planets, Venus, largely unexplored. Now, things are about to change.

In the latest announcement from NASA‘s solar system exploration program, Two missions have been greenlit, and both are heading to Venus. The two ambitious missions will launch between 2028 and 2030.

This marks a considerable change in direction for NASA’s planetary science division, which hasn’t sent a mission to the planet since 1990. It’s exciting news for space scientists.

Venus is a hostile world. Its atmosphere contains sulfuric acid and the surface temperature is high enough to melt lead. But it hasn’t always been that way. It is believed that Venus started out very similar to Earth. So what happened?

This image of Venus is a composite of data from NASA's Magellan spacecraft and Pioneer Venus Orbiter.
NASA will do two missions to Venus. (Photo: NASA)

Why explore Venus

While on Earth carbon is mostly trapped in rocks, on Venus it has escaped into the atmosphere, making it about 96 percent carbon dioxide. This has led to a runaway greenhouse effect, raising surface temperatures as high as 90 degrees Fahrenheit.

The history of the planet makes it a great place to study the greenhouse effect and learn how to manage it on Earth. We can use models that map the atmospheric extremes of Venus and compare the results to what we see at home.

But extreme surface conditions are one reason planetary exploration missions have avoided Venus. The high temperature means a very high pressure of 90 bar (equivalent to about a kilometer underwater) which is enough to instantly crush most planetary landers.

High temperature means very high pressure. (Photo: NASA/JPL/USGS)

Most of the exploration done so far was done by the then-Soviet Union between the 1960s and 1980s. There are a few notable exceptions, such as NASA’s Pioneer Venus mission in 1972 and the European Space Agency’s Venus Express mission in 2006.

The first landing occurred in 1970, when the Soviet Union’s Venera 7 crashed due to parachute meltdown. But it managed to transmit 20 minutes of data to Earth. The first surface images were taken by Venera 9, followed by Venera 10, 13 and 14.

The first mission to Venus

The first of NASA’s two selected missions will be known as “davinci“, an abbreviation for Deep Atmosphere of Venus Investigations of Noble Gases, Chemistry and Imaging. It includes a descent probe, which means it will drop through the atmosphere, taking measurements as it goes. The descent has three stages with the first investigating the entire atmosphere.

The probe will observe the composition of the atmosphere in detail, providing information about each layer as it falls. We know that sulfuric acid is confined to cloud layers about 30 miles up, and we know that the atmosphere is 97 percent carbon dioxide.

But the study of trace elements can provide insight into how the atmosphere ended up in this state. The second stage will seek lower altitudes to measure weather properties such as wind speed, temperature and pressure in detail.

The last stage takes high-resolution images of the surface. While this is very common on Mars, it has always been a challenge on Venus. The thick cloud cover means that visible light is reflected, so observation from Earth or from orbit is impractical.

The intense surface conditions also mean the rovers are impractical. One suggestion has been a balloon mission.

The second mission to Venus

The second mission is called Veritas, short for Venus Emissivity, Radio Science, InSAR, Topography and Spectroscopy. This will be a more standard planetary mission. The orbiter will carry two instruments on board to map the surface, supplementing Davinci’s detailed infrared observations.

The first of these is a camera that observes in a range of wavelengths. It can see through the clouds of Venus to investigate the atmospheric and soil composition. This task is very difficult, since the temperature of the surface causes the reflected light to have a very wide range of wavelengths. Veritas will compensate for this by using techniques that are often used to study the atmospheres of exoplanets.

Venus crosses one face of the Sun. (Photo: NASA/GODDARD)

The wavelength camera will also look for signs of water vapor. The Venus Express mission showed that the main elements escaping from Venus’ atmosphere are hydrogen and oxygen, so if there is water, it will be in small amounts or deep below the surface.

The second instrument is radar and uses a technique widely used on Earth observation satellites. A very large active radio receiver, important for high-resolution imaging, is simulated using radio pulses aimed at different angles in front of the spacecraft. The high-resolution radar images will create a more detailed map to investigate the evolution of the surface of Venus, as well as determine if there is tectonic or volcanic activity.

These missions could also add evidence to the theory that the surface of Venus completely melted and reformed 500 million years ago. This arose to explain the lack of meteorite impacts on the surface, but no evidence of a volcanic lava layer that would result from such resurgence has been found so far.

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