The planet Venus crosses the face of the sun. (Ian Waldie/Getty Images)
Venus passes between Earth and the sun as little more than a mote of dust, overlooked as ever beside our Martian dreams of water, life, footprints and flags. What would it be like to survey the Venusian surface firsthand — to set foot on Earth’s strange twin?
Assuming your imagined space suit protects you from Venus’ intense heat and crushing atmospheric pressure, the first thing you’ll notice will be the gloom.
“If you were suddenly transported to Venus, you would notice that the light seems very different from that on Earth,” says Denver Museum of Nature and Science astrobiologist David Grinspoon. “It’s always cloudy, and there’s a very thick atmosphere so the light is extremely diffuse and kind of reddish. There are no shadows because there’s no direct sunlight.”
It’s a planet where the days are dim, and the blackness of the night is broken only by the glow of red-hot rocks and towering volcanic peaks.
“Volcanism covers 80 percent of the surface,” says Suzanne Smrekar, a planetary scientist at NASA’s Jet Propulsion Laboratory. “It’s a very volcanic planet, with thousands and thousands of small-scale volcanoes and hundreds of large volcanoes.”
As you envision yourself strolling this hellish landscape, imagine a carbon dioxide-rich atmosphere mingled with wafts of sulfuric acid. The temperature outside your space suit is a searing 900 degrees Fahrenheit (482 degrees Celsius). It’s hot enough to melt lead, and the atmospheric pressure is nearly 100 times greater than that on Earth.
“If you were to walk around the surface, it would actually be more like walking through a fluid than a regular atmosphere,” says Smrekar.
The second planet from the sun may strike a harsh contrast to the conditions we know on Earth, but the more we understand about Venus, the more we come to understand our own world.
A view of Venus’ surface as photographed by the Russian Venera 13 lander in 1982. (NASA)
In many ways, Venus resembles a long-lost twin to Earth. It’s the only planet in our solar system that shares a similar size and composition to our planet and, more likely than not, the two worlds share similar origins.
“Venus could have been nearly identical to Earth in the beginning,” says Grinspoon, “and yet they have gone down very different paths in terms of how their climates and surface conditions have evolved. A runaway greenhouse effect boiled off its early oceans, and they were lost to space. The climate became stuck in a very desiccated and overheated condition. So, Venus is sort of a worst-case scenario of climate change on an Earth-like planet.”
Unsurprisingly, Venus has proven very useful to scientists in testing ideas about terrestrial environmental change. In fact, according to Grinspoon, studies of the Venusian atmosphere informed the scientific understanding of acid rain and Earth’s depleted ozone layer.
“Venus is a laboratory for understanding how the Earth works,” says Smrekar. “We expect it to be more like Earth, and because it’s not, it helps challenge our ideas about what we think we know about processes on Earth. For example, Earth is the only planet that has plate tectonics. Venus ought to as well, but it doesn’t. As we try to understand why, we learn a lot more about why plate tectonics actually exist on Earth.”
Venus’s absence of plate tectonics continues to offer planetary scientists a tantalizing mystery. Is the difference due solely to an orbit that takes it closer to the sun or are other factors involved, such as differing planetary interiors.
“We need more missions to know for sure,” says Grinspoon. “For those of us advocating new Venus missions, one of our prime motivations and arguments is that with the right data we could puzzle out this fascinating question surrounding the divergent evolutions of Venus and Earth.”
As with Mars, many questions remain regarding the cosmic curiosity of organic life.
A radar map of Venus’ surface imaged by the 1990-1994 Magellan mission. (NASA/JPL/USGS)
Was there ever life on this poisonous pressure cooker world? Might it thrive there even now? After all, Venus may have boasted oceans in its distant past. Why not the simple organisms that emerge there, too?
“Early in its history, Venus could have been a more hospitable place for life to form,” says Smrekar. “We might see evidence of early life in terms of minerals left at the surface and that has eventually led us to look at cloud environments on Venus today as a place where microorganisms could feasibly exist.”
Unlike the planet’s surface, Venus’ clouds are not particularly hot and possess the possible nutrients, energy sources and liquid water that life requires. It’s also possible that the same life that emerged on Venus in some primordial age lives on today on our own rocky planet.
“We don’t know that Earth life even started on Earth,” Grinspoon says. “It could have started on Mars, and it also could have started on Venus. We could all be Venusians as far as our distant ancestry is concerned. The young planets were exchanging materials and blasted rocks could have carried organisms from one world to the other. We don’t know for sure, but there is no reason to strongly doubt that Venus could have supported life.”
These and other mysteries of Venus remain unsolved, at least until more exploration missions come to fruition. Flybys aside, the United States hasn’t conducted a mission to Venus since 1989′s Magellan — although the European Space Agency currently has Venus Express in orbit around the planet.
“It’s been quite some time since we’ve had a dedicated Venus mission and a lot of us feel like it is time,” says Grinspoon, “especially given the timeliness of our questions about climate change. Several missions are currently under consideration at NASA, so it doesn’t seem like a completely vain hope.”