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Very close to us, cosmologically speaking, there is a planet almost identical to Earth. Venus is about the same size, made of more or less the same material, and formed around the same star.
For an alien astronomer light years away looking at the solar system through a telescope, it would be virtually impossible to distinguish Venus from our planet.
However, when the surface conditions of Venus are known – furnace temperature and an atmosphere saturated with carbon dioxide with clouds of sulfuric acid – it becomes clear that Venus has nothing to do with Earth.
How is it possible that two planets so similar in position, formation and composition could end up being so different? This is a question that concerns a growing number of members of the community of planetary scientists and that prompts many initiatives to explore Venus.
If the scientific community can figure out why it evolved the way it did, we will know with more certainty whether the existence of an Earth-like planet is the rule or the exception.
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Was Venus a blue planet in another era?
Current scientific opinion holds that at some point in the past, Venus had much more water than its dry atmosphere suggests today, possibly even oceans. But as the Sun got hotter and brighter (due to natural aging), Venus’ surface temperatures rose and eventually evaporated the oceans and seas.
The growing buildup of water vapor in the atmosphere created a runaway greenhouse effect on the planet from which Venus could not recover.
It is unknown if Venus ever had Earth-like plate tectonics (where the outer shell of the planet is broken into large moving pieces). Water is essential to the functioning of plate tectonics, and a runaway greenhouse effect would effectively stop this process, if it ever took place there.
But the end of plate tectonics would not have meant the end of geological activity: the planet’s considerable internal heat continued to produce magma, which spread as voluminous lava flows and reconfigured most of its surface.
Indeed, the average age of its surface is about 700 million years old, no doubt an advanced age, but very young if we compare it to the surfaces of Mars, Mercury or the Moon, which have several billion years.
exploration of the second planet
The vision of Venus as a wet world is only a hypothesis: the planetary scientific community does not know what makes Venus so different from Earth, or whether the two planets were in fact generated under the same conditions.
Humans know less about Venus than we do about other planets in the inner solar system, largely because Venus poses several unique obstacles to exploration.
For example, it must be explored by radar to penetrate the opaque clouds of sulfuric acid and see the surface. The difficulty is much greater than with the surfaces of the Moon or Mercury, which can be easily observed.
In addition, the high surface temperature –470℃– makes conventional electronics only last a few hours. A very different situation from Mars, where vagabond They can work for more than ten years. So, in part because of the heat, acidity and opacity of the surface, Venus has not benefited from a sustained exploration program over the past two decades.
Yet in the 21st century, two missions have been sent to Venus: the European Space Agency’s Venus Express satellite, which operated between 2006 and 2014, and the Japan Aerospace Exploration Agency’s Akatsuki probe, which is currently in orbit.
little interest
Human beings have not always shown so little interest in Venus. It was once the darling of planetary exploration: between 1960 and 1980, some 35 missions were sent to the second planet. The Mariner 2 mission was the first space probe to successfully conduct a planetary rendezvous, flying past Venus in 1962.
The first images taken from its surface returned by the Soviet Venera 9 probe module after it landed on Venus in 1975. And the Venera 13 lander was the first spacecraft to send sounds from its surface.
But NASA’s last mission to Venus was the Magellan probe, in 1989. This probe took radar images of nearly the entire surface before its predicted demise in the planet’s atmosphere in 1994.
Return to Venus?
Several NASA missions to Venus have been proposed in recent years. The most recent planetary mission NASA has chosen is a nuclear-powered spacecraft called Dragonfly bound for Saturn’s moon Titan, but a proposal to measure the composition of the surface of Venus has also been selected and will receive a support to further develop its technology.
Other missions under consideration are a European Space Agency project that aims to map the surface of Venus in high resolution and a Russian plan that aims to build on its legacy as the only country to successfully placing a lander on the surface of Venus.
Some 30 years after NASA set sail for our infamous neighbour, the future of Venus exploration looks bright. But sending a single mission – a radar-equipped orbiter or even a long-duration lander – won’t solve all the remaining mysteries.
On the contrary, a sustained program of exploration is needed to raise our knowledge of Venus to the level of knowledge we have of Mars or the Moon. To achieve this, it will take time and money to invest, but, in my opinion, it is worth it.
If we can understand why and when Venus became the planet it is today, we will better understand how an Earth-sized world can evolve when located near its star. And, under an increasingly bright Sun, Venus could even help us understand the fate of Earth itself.
Character font: Paul K. Byrne / THE CONVERSATION
Reference article: https://theconversation.com/why-should-we-go-back-to-venus-122507