In the latest announcement from NASA’s solar system research program, two missions were given the green light – both aimed at Venus. The two ambitious missions will start between 2028 and 2030.
This marks a significant change in the direction of NASA’s planetary science unit, which has not sent a mission to the planet since 1990. This is exciting news for space scientists like me.
Venus is a hostile world. Its atmosphere contains sulfuric acid and surface temperatures are hot enough to melt the lead. But this has not always been the case. It is believed that Venus began very much like Earth. And what happened?
While on Earth carbon is trapped mainly in rocks, on Venus it escaped into the atmosphere ̵
The history of the planet makes it an excellent place to study the greenhouse effect and to learn how to govern the Earth. We can use models that draw the atmospheric extremes of Venus and compare the results with what we see at home.
But extreme surface conditions are one of the reasons planetary missions avoid Venus. The high temperature means a very high pressure of 90 bar (equivalent to approximately one kilometer under water), which is enough to immediately crush most planetary landings. Then it may come as no surprise that missions to Venus were not always planned.
Most of the research carried out so far was carried out by the then Soviet Union between the 1960s and 1980s. There are some 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 took place in 1970, when the Soviet Union’s Venus 7 crashed due to the melting of the parachute. But it managed to transmit 20 minutes of data back to Earth. The first surface images were made by Venus 9, followed by Venus 10, 13 and 14.
The descent mission
The first of NASA’s two selected missions will be known as Davinci + (short for Venus Deep Atmosphere Research on Noble Gases, Chemistry, and Imaging). It includes a descent probe, which means that it will be released through the atmosphere, taking measurements as it walks. The descent has three stages, the first exploring the entire atmosphere.
The probe will examine the composition of the atmosphere in detail, providing information on each layer as it falls. We know that sulfuric acid is limited to clouds about 50 km (30 miles) up, and we know that the atmosphere is 97 percent carbon dioxide.
But the study of trace elements can provide information about how the atmosphere got into this state. The second stage will be to consider lower altitudes to measure meteorological properties such as wind speed, temperature and pressure in detail.
The last stage makes high-resolution surface images. Although this is very common for Mars, Venus has always been a challenge. The thick cloud layer means that visible light is reflected, so observation from Earth or orbit is not practical. Intense surface conditions also mean that rovers are impractical. One suggestion is a balloon mission.
We have a low-resolution image of the surface of Venus, thanks to a mission by Nasa Magellan in 1990, which mapped the surface using radar. The Davinci probe will make surface images using infrared light during its descent. These images will not only allow better planning of future missions, but will also help scientists study how the surface formed.
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, complementing Davinci’s detailed infrared observations.
The first is a camera that monitors in a range of wavelengths. He can see through the Venusian clouds to study the atmospheric and terrestrial composition.
This task is very difficult because the surface temperature causes the reflected light to have a very wide range of wavelengths. Veritas will compensate for this by using techniques often used to study the atmosphere of exoplanets.
The wavelength camera will also look for signs of water vapor. The Venus Express mission has shown that the main elements that avoid the Venusian 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 images – is simulated using radio pulses directed at different angles in front of the spacecraft.
High-resolution radar images will create a more detailed map to study the surface evolution of Venus, as well as determine if there is any tectonic or volcanic activity.
These missions could also add evidence to the theory that the Venusian surface was completely melted and reformed 500 million years ago. This is due to the explanation for the lack of meteorite impacts on the surface, but so far no evidence has been found of a volcanic lava layer that would result from such a restoration.
It is exciting that NASA has directed its planetary mission to Venus. For all novice astronauts, I’m afraid the chance of sending a man there soon doesn’t exist. But the information that can be obtained from the largely forgotten sister of the Earth will be very valuable for understanding our world.
(This article was syndicated by PTI from The Conversation)