Venus

The planet Venus has been gracing our early evening skies for weeks now – shining out like a beacon. Usually when this happens, planetariums and observatories get a lot of phone calls from people wondering what that bright thing is up there. Back when I worked at a planetarium, we’d inevitably get a few calls from people who swore they were seeing a UFO (meaning some kind of space ship) hovering in the western sky after sunset.

Venus is a very interesting place. For a long time, scientists referred to it as the twin of Earth. Given what we know NOW about Venus, I’d have to say that it is the thoroughly unpleasant cousin of Earth. How so?

For starters, Venus is covered with clouds. They never clear away and the only way to probe beneath them is to either a) send a spacecraft through them (which we’ve done) or b) send radar waves through them to bounce off the surface (which we’ve also done). The spacecraft views of the Venus surface are pretty darned forbidding.

The Magellan mapping mission (which used radars to “image” the surface) showed the same thing. Long-term studies of the planet basically tell us that this place is a volcanic desert. Its extremely dense atmosphere is laden with carbon dioxide and sulfuric acid clouds. It’s not a place where humans could reasonably expect to explore once, much less settle down and colonize. That last fact pretty much ruled out a lot of old-fashioned science fiction tales that hypothesized a damp, foggy planet run by dinosaurs and lizards.

But, the big question now is whether Venus was always a hellish cousin or could it have been a pleasant place at one time early in its history? That’s the story that science writer Bruce Dorminey explores in a recent issue of Nature Magazine. He describes new research into and analysis of data from the Galileo spacecraft that may point to a more Earth-like period in Venus’s history, a time when oceans may have covered the planet and that Venus may have experienced plate tectonics and maybe even the conditions where life could have formed.

What’s the evidence for this supposition? In an interesting interpretation of the Galileo data, George Hashimoto of Okayama University in Japan, points out that Venus’s highlands regions emit less infrared radiation than the lowlands. He interprets this to mean that the highlands are made of “felsic” rocks (like granite, for example) that require water in order to form. Furthermore, tectonic motions may have formed continents on Venus, and water and carbon may have been cycled between the atmosphere and the mantle. Hashimoto published his findings in the Journal of Geophysical Research at the end of 2008.

If this research bears out, it could mean that perhaps at some point in the past, Venus had plenty of water and may have been habitable. Whether it was welcoming to life is another matter NOT discussed in these papers, but of course people are interested in knowing if Venus could have supported life in the past. It’s an intriguing finding and it really does beg the question that if Venus were that hospitable in the past, what could have happened to turn it into the hellhole we see today?

Of course, there are researchers who do not agree with the finding and are actively challenging Hashimoto’s hypothesis. That’s the way science works, of course. And, it will lead researchers to further examination of data from the Venus Express mission and the Venus Climate Orbiter (a Japanese Space Agency mission) when it reaches the planet after its 2010 launch.

So, think about that the next time you gaze up at Venus. That bright, starlike object may well have an exciting past that we are just beginning to know.