Monday, April 12, 2010

Volcanic Venus

Venus is the brightest object in the night sky (not including the moon) and the hottest object in our solar system (not including the sun). This planet is super-weird and really intriguing. It is a little bit smaller than Earth, has no moon, has a smaller than expected magnetic field, and rotates very slowly and in the wrong direction. Its year is 244.6 days long and its day is 243 days long. The planet is covered in a thick layer of clouds that are very good at reflecting light (= has a high albedo). The atmosphere is 96.5% carbon dioxide, which traps an extrodinary amount of heat on the planet (a runaway greenhouse effect). It is thought that, at one point in history, Venus may have had oceans, but as the temperature increased they evaporated, UV light broke up the water molecules, and all this increased the greenhouse effect. Radar imaging of the surface, particularly by the Magellan probe in the early 1990's, has given detailed maps of the planet. This imaging has shown a distinct lack of craters, expected when the thick sulfuric atmosphere burns up all but the largest asteroids/meteors. But even these big craters are only about 500 million years old, suggesting that the planet has entirely resurfaced itself (likely caused by a lack of plate tectonics).

In a new online Science paper, evidence is presented that suggests that Venus is still reshaping its surface and cooling its interior via volcanic outpourings. As I said above, it is thought that a dramatic planetary resurfacing event may have occurred 500 million years ago, and this paper suggests that Venus also steadily resurfaces itself through smaller volcanic events. In addition to young craters, the Magellan probe also found nine "hot spots", low rises each a couple of thousand kilometers across, from which lava has more recently flowed. Gravity measurements taken by the probe also revealed plumes of hot rock slowly rising beneath these hot spots that may feed the eruptions. However, the age of the lava flows was unknown.

Planetary scientists from NASA's Jet Propulsion Laboratory (JPL) have taken a look at three of these hot spots using the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on the European Space Agency's Venus Express, still in orbit. Using VIRTIS, the scientists found that the hot spots radiate more heat than the rest of the planet, and were able to infer that the hot spot flows are still pretty fresh an unweathered. Calculations of the flow ages range from a few million years down to 2500 years (young when we are talking planetary history), and the researchers suggest that they are slow, steady outpourings.

Here's the story: http://www.sciencemag.org/cgi/content/full/328/5975/157-a
and www.sciencemag.org/cgi/content/abstract/science.1186785
and a NYT article including video: http://www.nytimes.com/2010/04/10/science/space/10venus.html?ref=science
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