By akademiotoelektronik, 26/11/2022

Venus, our close cousin with scorching weather Back to Clubic homepage

Eric BottlaenderSpace specialistApril 13, 2021 at 5:03 p.m.13Venus, seen by the Venus Express probe. © ESAA neighbor of the Earth, of the same size, accessible in a few months' journey? You can easily find her in the night sky, it's Venus of course!But make no mistake: on the spot, it's hell.

Close cousin

Given that he second most visible object in the night sky after the Moon, it's safe to say that humans have been observing Venus for tens of thousands of years. It is even sometimes still given its old name "Etoile du Berger", even if it is technically incorrect... Venus is the second closest planet to the Sun, which it orbits at a distance of about 108 million kilometers. Like its smaller cousin Mercury, it has no moon, and in fact shares several characteristics with Earth. A diameter very close to that of the latter (12,103 km), a mass which is also close to it, the presence of an atmosphere, volcanism, and even conditions which were perhaps conducive to life, there a few billion years ago. So why so few bookings for trips to Venus? Venus and its clouds, seen by the Pioneer Venus Explorer probe. © NASA

Highway to Hell

A popular adage has it that "women are from Venus"... If so, it's easy to see why they left. For starters, there's the atmosphere. This is particularly dense and made up of more than 96% CO2. There are also the winds, which blow at more than 300 km/h (up to 700 km/h at an altitude of approximately 55 km), the clouds with droplets of sulfuric acid, and a pressure at ground level which reached... 92 bars (i.e. the equivalent of the pressure that would be exerted at a depth of 910 meters, on Earth)! If you are still hesitating, know that Venus also offers the highest average temperatures in the Solar System (excluding ) with 467°C in the shade, on average. Clearly the most horrible conditions possible. The landscapes are monochrome gradients between yellow and orange, and the planet experiences Venus quakes, eruptions, or even both, even though there is no plate tectonics and even if no flow of lava has yet been observed - which would complement the postcard nicely.

We are aiming for Venus, but...

Just imagine that despite these extreme characteristics, the exploration of Venus , due to its proximity to the Earth, has made great progress in 60 years of space adventures. The first mission to Venus took off from the USSR before Yuri Gagarin! Well, unfortunately, it is one of the many failures of the time. It will indeed be necessary to wait until December 14, 1962 for the American probe Mariner-2 to fly over Venus, a few tens of thousands of kilometers from its surface, thus managing to measure the temperature of its atmosphere. However, it must be admitted that the Soviets did not lack determination. After 12 failures in a row (including missions that almost succeeded), the Venera 4 probe was the first to transmit data through the atmosphere of Venus. One of the most accurate radar readings of the surface of Venus, by the Magellan orbiter. © NASA

Communist planet

For more than 20 years thereafter, and until the fall of the USSR, Venus was a formidable playground for Soviet space technology, which wrote its letters of nobility there ( failing to succeed on Mars). In 1973, the Venera 8 probe became the very first lander to land and transmit data from the ground of another planet, Venus. In October 1975, a new first for the USSR, which became the first to photograph the surface of Venus with Venera 9 and 10 (the Americans only managed to land successfully on the surface of Mars six months later). The success of the Venera missions will continue until the beginning of the 1980s, with the exceptional panoramas of the arid surface of Venus, and a veritable collection of other data less appreciated by the general public. But landing in hell is an unforgivable exercise: despite their size and foolproof design, the Venera probes will not last more than an hour and a half on the surface. The surface of Venus seen by the Venera 13 probe

Cosmopolitan missions

Between 1990 and 1994, NASA piloted the Magellan probe, which managed a complete mapping of the planet thanks to its high-resolution radar, delivering snapshots unmatched today. More recently, other missions have focused on Venus' atmosphere (Venus Express, ESA) and even specifically on its clouds and wind currents (Akatsuki, JAXA, the only probe still active in orbit today).If it is not shunned by scientists who regularly request new missions to study Venus, decision-makers do not have the same attraction for Venus as for its cousin Mars. However, we must expect new discoveries in the decade to come: several missions are in preparation to go and map its surface with new precision, cross its atmosphere, make small robots survive for several hours on its soil or even, futuristic luxury. , send airships on long-distance missions in the upper atmosphere. Artist's impression of a concept robot on the Venus surface. © NASA/JPL-CaltechFun fact: A year on Venus lasts 224.7 Earth days, and that's less than a sidereal day (time for the planet to spin around on it- same) on the surface of Venus, which lasts 243 Earth days! Its rotation is indeed very slow (and upside down compared to all the planets of the Solar System, except Uranus), at least on the surface. Because the winds at high altitude, they form a continuous jet stream. And for tourists? The duration of a solar day is all the same 116 days...Tourist notes:-Travel 8/10: Provided you leave when Venus is close to the Earth, the trip only lasts four months, which is far from unpleasant. Imagine that this was even seriously considered in the 70s (overflight, then return in stride).-Landscapes 3/10: Despite some canyons and mountains (a few peaks over 5,000 m in Beta Regio), there are a lot of plains and anyway, you can't see much there. It may have been pretty, but that was before.-Livability 1/10: The ground is solid. That's about the only positive feature. Everything else is constantly trying to kill you.