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The surface of Venus, as imaged by the Magellan spacecraft's radar. (NASA/JPL)

Venus Is More Than Just a Cautionary Tale

Venus shines more brightly in Earth’s sky than any of our stars, but it gets surprisingly little attention nowadays (unless it’s being used as an example of a planetary What Not To Do).

Not that long ago, though, humans seemed rather interested in hurling tons of hardware at our sister planet, which is roughly the same size as Earth. From the 1960s through the early 1980s, Venus was the target of 19 Soviet space missions. The Venera program launched 16 probes at the cloudy world and managed to grab several photos from the planet’s parched surface. NASA has sent a half-dozen spacecraft to the planet – the most recent being Magellan, which orbited Venus between 1989 and 1994, and mapped 98 percent of the planet’s surface.

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Venera 13 Lander image of the surface of Venus. The probe survived on the surface for two hours, in 1982. (Soviet Planetary Exploration Program/NASA)

It took nearly a decade for the next spacecraft to arrive at our nearest neighbor. Since 2006, the European Space Agency’s intrepid Venus Express spacecraft has been exploring the sulfuric planet. The mission has revealed much about the mysterious world that hides beneath its cloudy shroud. But later this year, when the spacecraft plunges through the 250-kilometer thick clouds and falls to the planet’s surface, Venus will again be alone. At least until next year, when the Japanese space probe Akatsuki is supposed to arrive. Our sister planet was once rather Earthy in many respects, so Earthy that it’s possible life may have gained a feeble foothold early on. Billions of years ago, scientists say, Venus had oceans, and a pleasant climate. But those oceans evaporated and the planet fell prey to a runaway greenhouse effect. The once-friendly, fertile world was transformed into a roasting, hellish home.

Anyway. In addition to its role as a warning to others, Venus offers a wealth of fun and crazy facts. Here are a few Venusian wonders.

1. Venus endlessly traces the same series of five shapes in Earth’s sky. The Mayans used these shapes, and Venus, as a basis for their cosmology and calendar.

2. Venus will always be a morning or evening “star.” It will never be a mid-day star, as Mars and Jupiter can be, because it orbits in between the sun and Earth.

3. The surface of Venus, at roughly 840 degrees F, is the hottest place in the entire solar system (aside from the sun, of course). It’s even hotter than Mercury.

4. Difference in temperature between day and night on Venus: 0 degrees.

5. Difference in temperature between the planet’s equator and poles: 0 degrees.

6. Reason for #4 and #5: That enormously thick, carbon dioxide atmosphere redistributes heat very efficiently. In other words, if you’re on Venus and you need to cool off, your best bet is to go up. Roughly 30 miles up, where the pressure and temperature finally relax and become something Earth-like (see #8).

7. But you wouldn’t want to be on Venus, because you’d die. The pressure on the planet’s surface is 90 times that of Earth (so, roughly the equivalent of being beneath 8,000 feet of water).

8. That doesn’t mean the planet is necessarily lifeless. It’s possible that organisms could live in those acid clouds, which contain water, energy, and nutrients.

9. Also, Venus might be actively volcanic. Scientists are still working on sorting this out, but evidence from the surface suggests geologically recent volcanic eruptions (within the last million years).

10. Greenhouse gases create efficient incubators. Venus’ thick shroud reflects roughly 80 percent of the sunlight that hits the planet. This means that the small amount of sunlight that does get through is enough to superheat the planet – thanks to those gases and that massive atmosphere.

Thank you to astrobiologist David Grinspoon, author of Venus Revealed, for helping me with this post!