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Colored perspective mosaic of the Vesusian surface of Venera 9. Photos by the Venera 9 team, processing by Don P. Mitchell
Compared to Earth, our astronomical neighbor Venus is 95 percent bigger, 28 percent closer to the Sun and almost identical in planetary composition. However, if one were to spend a day on the surface of Venus – from one sunrise to the next – one would be faced with a considerable number of obstacles and novelties.
Assuming you could survive the journey through clouds of sulfuric acid to get to the surface, survive the lead-melting heat, withstand the air pressure comparable to a sea depth of 800 meters, and remain stationary against the constant thick breeze, the sun wouldn’t actually be Visible as a single point, as all the sunlight is scattered through a planet-wide cover of almost opaque clouds.
The sun would rise in the west rather than east because Venus is “retrograde” and spins in the opposite direction of the sun and most of the other planets in the solar system. One hypothesis is that the planet was once “progressive” like most others, but that its spin was reversed billions of years ago by two massive planetoid impacts. Another hypothesis suggests that Venus’ original progressive spin was unstable because the planet’s core, mantle, and atmosphere move at different speeds. The friction between these layers may have caused increasing wobble across the planet, ultimately causing Venus to tip over. If this hypothesis is correct, then Venus is upside down rather than backwards.
The rotation of Venus is also very slow. A full-day visit to Venus’ equator would include 1,401 hours of uninterrupted sunlight – or about 58 Earth days. At this speed, a quick jog would be enough to keep the sunspot in the sky. After sunset, an additional 1,401 hours of darkness would be observed, although the temperature would not change after dark. Venus has become isothermal due to the greenhouse effect and has an average temperature of 420 ° C (788 ° F) at any point on the planet: both poles and the equator, day and night. The coolest point on the planet’s surface is at the top of its highest mountain, Maxwell Montes, where the temperature drops to 382 ° C. There you could see a heavy metal “snow” made of lead sulfide and bismuth sulfide.
Venus completes an orbit of the Sun every 224.7 Earth days, so a Venusian year is almost – but not quite – two Venusian days.
In the 1970s, the Soviet Union sent a number of Venera probes to Venus with various scientific instruments. The heat and pressure troubled the probes and their surface operating times were measured in just a few minutes. On October 22, 1975, Venera 9 was the first probe to return images of the surface of another planet and, thanks to an ingenious liquid cooling system, survived for almost an hour.
During the space race, the United States also had a visit to Venus in mind. In the mid-1960s, NASA designed a manned flyby mission to Venus with modified Apollo hardware. The launch was scheduled for Halloween 1973, with a Venus flyby on March 3, 1974 and return to Earth on December 1, 1974. After launch, the astronauts had about an hour to abort the mission in the event of a problem After that time, they would run out of fuel to return to Earth by any means other than a sling around Venus. The mission was scrapped for budget reasons.
In 2020, scientists reported the discovery of phosphine in Venus’ atmosphere, which could be an indicator of the life of microbes in the air. However, since these data did not fare well in the subsequent review, it is likely that Venus is a lifeless planet.