by Bill Morris
Like many people in Otago I went out stargazing on Wednesday to observe the passing of the planet Venus across the face of the Sun. It was a momentous occasion, a chance to peer across the space that separates us from our mother star and get a real perspective on where things sit in relation to one another.
What is Venus? A planet similar in size to Earth but, being closer to the Sun, one that has been cooked at a much higher temperature than we have. There is a theory that when the Sun was in its earlier state it was much smaller and at that time, Venus may have been inhabitable for life as we know it. However as the sun expanded and heated up, it triggered a “runaway greenhouse” effect on Venus that turned it into a Hadean inferno with a crushing and toxic atmosphere.
Venus has no apparent plate tectonics, perhaps due to the fact that water, which is important in plate tectonics on Earth, has been almost totally evaporated from its surface. It is studded with hundreds of thousands of volcanoes belching carbon dioxide into the dense atmosphere.
Exploration of Venus goes back to the days of the Space Race, when America and the USSR competed with one another to push out the frontiers of the known Universe. The Americans got to Venus first – the Mariner 2 becoming the first successful interplanetary mission when it flew by Venus in 1962.
The Russian Venera missions repeatedly penetrated the atmosphere of Venus for two decades between 1963 and 1983, with later missions surviving the crushing atmosphere to land on the surface. The Venera 10 sent back the first images of the surface of the planet. Venera 13 and 14 returned the first colour images. They revealed a place of strange inhospitable beauty, strangely serene yet utterly parched.
All these landers lasted less than an hour on the surface, succumbing to intense temperatures of up to 450 degrees Celsius and the dense atmosphere, which at the surface has the equivalent pressure of that one kilometer below the surface of Earth’s ocean. The Vega missions in the early 1980’s were the last landings on the surface of Venus.
It has been proposed that humans could colonize Venus in the future and survive by living in enclosed floating cities about 50 km above the surface. In this portion of Venus’ atmosphere, temperature and pressure are similar to that on Earth.
For now, however, it appears our colder neighbor Mars is of more interest to NASA and space exploration in general and it may be a long time before a manned mission to Venus is seriously contemplated. And so at 4:43 pm on Wednesday afternoon, it slipped off the edge of the Sun’s disc and into the blackness of the space, once more to travel on without us.