Article: Venus Can Have 'Comet-Like' Atmosphere

When the solar wind dies down, an outer layer of Venus's atmosphere billows outward (illustrated on right), making the second planet from the sun look like a comet.

  

The planet Venus sometimes looks less like a planet and more like a comet, scientists say.

Scientists with the European Space Agency have discovered that a part of the upper atmosphere of Venus — its ionosphere — acts surprisingly different depending on daily changes in the sun's weather. The side of Venus' ionosphere that faces away from the sun can billow outward like the tail of a comet, while the side facing the star remains tightly compacted, researchers said.

The discovery was made using ESA's Venus Express spacecraft, which observed Venus's ionosphere during a period of low solar wind in 2010 to see exactly how the sun affects the way the planet's atmosphere functions. In 2013, the sun is expected to reach the peak of its 11-year solar activity cycle.

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