Popular science fiction from the early 20th century portrayed Venus as a kind of wonderful world with pleasant temperatures, forests, swamps, and even dinosaurs. In 1950, Hayden's Planetarium at the American Museum of Natural History made reservations for the first space tourists, well before the modern era of Blue Origins, SpaceX and Virging Galactic. All you had to do was indicate your address and put a tick in the right place, among which was Venus.
Venus is unlikely to be a dream come true for aspiring space tourists today. As numerous missions over the past few decades have shown, this planet is not a paradise, but a hellish world of high temperatures, a toxic atmosphere and colossal surface pressure. Despite this, NASA is currently working on a conceptual manned mission to Venus - the High Altitude Venus Operational Concept (HAVOC).
Mission to Venus: is it even possible?
How is such a mission even possible? Temperatures on the planet's surface (about 460 degrees Celsius) are higher than on Mercury, although Venus is twice as far from the Sun. At this temperature, most metals melt, including bismuth and lead, which can then fall out as "snow" on high mountain peaks. The planet's surface is a barren rocky landscape with vast basalt plains dotted with volcanic craters and several mountainous regions of continental proportions.
The planet is also geologically young and is undergoing catastrophic surface rework events. Extreme events are caused by heat build-up below the surface, causing the surface to melt, generate heat, and solidify again. An eerie prospect for any visitor.
Swimming in the atmosphere
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Because of this, the idea behind NASA's new mission is not to land people on an inhospitable surface, but to use the dense atmosphere as a ground for research. The official date for the HAVOC mission has not yet been publicly announced. The mission will be long term and will probably include several test missions that will have to prove the success of the entire event. Currently, such a mission is indeed possible using modern technology. The plan is to use airships that can remain in the upper atmosphere for extended periods of time.
Ironically, the upper atmosphere of Venus is the closest to Earth of any place in the solar system. Between heights of 50 and 60 kilometers, pressure and temperature can be compared to areas of the Earth's lower atmosphere. The atmospheric pressure in Venus's atmosphere at an altitude of 55 kilometers is about half the pressure at sea level on Earth. In fact, you'll feel great even without a squeeze suit - the same pressure can be found at the peak of Mount Kilimanjaro. You won't even have to warm up - the temperature will be within 20-30 degrees.
The atmosphere above is also dense enough to protect astronauts from ionizing radiation from space. The proximity of the sun also provides more available radiation than on Earth, which can be used to generate energy (about 1.4 times that).
The concept airship will float around the planet, carried by the winds. It could be filled with a breathable mixture of oxygen and nitrogen and thus provide buoyancy. This is realistic because breathable air is less dense than Venus's atmosphere and will rise.
The atmosphere of Venus is 97% carbon dioxide, 3% nitrogen and trace amounts of other gases. It contains sulfuric acid, which forms dense clouds and is the main factor responsible for the planet's visibility from Earth. Venus reflects about 75% of the light falling on it from the Sun. This reflective layer is between 45 and 65 kilometers in height, and the haze of sulfuric acid droplets reaches up to 30 kilometers down. Thus, the design of the airship must be resistant to the corrosive effects of this acid.
Fortunately, we already have the technology needed to overcome acidity problems. Several commercially available materials, including Teflon and a number of plastics, are highly acid resistant and can be used for the outer shell of an airship. With all these factors in mind, perhaps you could walk the platform outside the airship wearing a chemical protection suit and an oxygen tank.
Life on Venus?
The surface of Venus was mapped from orbit by the radar of the Magellan mission. However, we were able to visit only a few places on the surface, thanks to the Soviet Venera probes of the late 1970s. These probes gave us the first and so far the only images of the surface of Venus. Of course, the conditions on the surface seemed to us completely inhospitable for life.
However, the upper atmosphere is a different story. There are already several types of extremophilic organisms on Earth that can withstand conditions in the atmosphere at the altitude at which HAVOC will fly. Species such as Acidianus infernus can be found in highly acidic volcanic lakes in Iceland and Italy. It has been found that microbes are also carried in Earth's clouds. None of this proves that life exists in the atmosphere of Venus, but a HAVOC-style mission could explore that possibility.
The current climatic conditions and composition of the atmosphere are the result of a growing greenhouse effect (an extreme greenhouse effect that cannot be reversed) that has transformed the planet from a hospitable "sister of the Earth" into the monster it is today. While we do not expect the Earth to go through a similar extreme scenario, it demonstrates that dramatic changes in the planet's climate can occur when certain physical conditions occur.
By testing our current climate models using the extremes we see on Venus, we can more accurately determine how different effects on climate can lead to dramatic changes. Venus gives us the opportunity to test our climate modeling with all the ensuing consequences for the ecological health of our planet.
We still know relatively little about Venus, even though it is our closest planetary neighbor. Ultimately, studying the similarities between the two planets will help us understand the evolution of the solar system and possibly other stellar systems.
Ilya Khel