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Explained: European Space Agency’s EnVision mission to Venus

EnVision is an ESA led mission with contributions from NASA. It is likely to be launched sometime in the 2030s.

Artist impression of ESA's EnVision mission at Venus. (Source: European Space Agency)

Following NASA’s footsteps, the European Space Agency (ESA) on Thursday announced that it has selected EnVision as its next orbiter that will visit Venus sometime in the 2030s. Last week, NASA selected two missions to the planet Venus, Earth’s nearest neighbour. The missions called DAVINCI+ and VERITAS have been selected based on their potential for scientific value and the feasibility of their development plans. NASA is expected to allot $500 million to each of these missions that will launch between 2028-2030.

So what is EnVision?

EnVision is an ESA led mission with contributions from NASA. It is likely to be launched sometime in the 2030s. The earliest launch opportunity for EnVision is 2031, followed by 2032 and 2033. Once launched on an Ariane 6 rocket, the spacecraft will take about 15 months to reach Venus and will take 16 more months to achieve orbit circularisation.

The spacecraft will carry a range of instruments to study the planet’s atmosphere and surface, monitor trace gases in the atmosphere and analyse its surface composition. A radar provided by NASA will help to image and map the surface.

EnVision will follow another ESA-led mission to Venus called ‘Venus Express’ (2005-2014) that focussed on atmospheric research and pointed to volcanic hotspots on the planet’s surface. Other than this, Japan’s Akatsuki spacecraft has also been studying the planet’s atmosphere since 2015.

Why are scientists interested in studying Venus?

At the core of the ESA’s mission is the question of how Earth and Venus evolved so differently from each other considering that they are roughly of the same size and composition. Venus is the hottest planet in the solar system because of the heat that is trapped by its thick cloud cover.

“What history did Venus experience to arrive at this state and does this foretell Earth’s fate should it, too, undergo a catastrophic greenhouse effect? Is Venus still geologically active? Could it have once hosted an ocean and even sustained life? What lessons can be learned about the evolution of terrestrial planets in general, as we discover more Earth-like exoplanets?” these are the key questions that ESA’s mission aims to answer.

On the other hand, the results from DAVINCI+ are expected to reshape the understanding of terrestrial planet formation in the solar system and beyond. Taken together, both missions are expected to tell scientists more about the planet’s thick cloud cover and the volcanoes on its surface.

Further, scientists speculate about the existence of life on Venus in its distant past and the possibility that life may exist in the top layers of its clouds where temperatures are less extreme.

Last year, a team of scientists reported that they had found phosphine gas (a chemical produced only through biological processes) in the atmosphere of Venus that triggered excitement in the scientific community that some life forms might be supported by the planet. But the existence of life on the planet is nearly impossible given the high temperatures of Venus and its acidic atmosphere. Even so, this discovery could mean that life forms could have existed on Venus before when it was habitable. As per this theory, the discovery of phosphine could simply be remnants from the past.

About Venus

For those on Earth, Venus is the second-brightest object in the sky after the moon. It appears bright because of its thick cloud cover that reflects and scatters light. But while Venus, which is the second closest planet to the Sun, is called the Earth’s twin because of their similar sizes, the two planets have significant differences between them.

For one, the planet’s thick atmosphere traps heat and is the reason that it is the hottest planet in the solar system, despite coming after Mercury, the closest planet to the Sun. Surface temperatures on Venus can go up to 471 degrees Celsius, which is hot enough to melt lead, NASA notes.

Further, Venus moves forward on its orbit around the Sun but spins backwards around its axis slowly. This means on Venus the Sun rises in the west and sets in the East. One day on Venus is equivalent to 243 Earth days because of its backward spinning, opposite to that of the Earth’s and most other planets. Venus also does not have a moon and no rings.

Have humans visited Venus?

Because of the planet’s harsh environment, no humans have visited it and even the spacecraft that have been sent to the planet have not survived for a very long time. “Venus’ high surface temperatures overheat electronics in spacecraft in a short time, so it seems unlikely that a person could survive for long on the Venusian surface,” NASA says.

So far, spacecraft from several nations have visited the planet. The first such spacecraft was the Soviet Union’s Venera series (the spacecraft, however, could not survive for long because of the planet’s harsh conditions), followed by NASA’s Magellan Mission that studied Venus from 1990-1994. As of now, Japan’s Akatsuki mission is studying the planet from Orbit.

Which missions did NASA announce?

Both missions called DAVINCI+ and VERITAS are part of the space agency’s Discovery Program, which began in 1992 to give scientists the chance to launch some missions that use fewer resources and have shorter developmental times. The two selections are a part of the ninth Discovery Program and were made from proposals submitted in 2019.

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What do these missions plan to achieve?

DAVINCI+ is short for ‘Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging’ and is the first US-led mission to the planet’s atmosphere since 1978. It will try to understand Venus’ composition to see how the planet formed and evolved. This mission also consists of a descent sphere that will pass through the planet’s thick atmosphere and make observations and take measurements of noble gases and other elements.

Significantly, this mission will also try to return the first high resolution photographs of a geological feature that is unique to Venus. This feature, which is called “tesserae” may be comparable to Earth’s continents, NASA says. The presence of tesseraes may suggest that Venus has tectonic plates like Earth.

The second mission called VERITAS is short for ‘Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy’ and will map the planet’s surface to determine its geologic history and understand the reasons why it developed so differently from Earth.

VERITAS will orbit Venus with a radar that will help to create a three dimensional reconstruction of its topography which might be able to tell scientists if processes such as plate tectonics and volcanism are still active there. This mission will also map the emissions from Venus’s surface that may help in determining the type of rocks that exist on Venus–a piece of information that is not exactly known yet. It will also determine if active volcanoes are releasing water vapour into the atmosphere.

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