How Did Venus Get Hot?
The more intriguing question regarding Venus’ fever is how it got that way. The Venus Express probe has detected water vapor in the upper layer of clouds, and hydrogen and oxygen in other layers—signs of water. There are also surface features that indicate Venus may once have been a much different world, with oceans and perhaps vegetation.
German researchers have identified rocks in some areas that look like granite. Granite is formed when basalt is forced beneath plates by tectonic forces, mixes with water and is pushed back to the surface by volcanic activity. The Venus Express has added one more piece to this puzzle. Radar imaging has indicated that Venus’ highland plateaus were once continents surrounded by oceans.
So where did the water go?
One clue is Venus’ lack of a magnetic field. The Venus Express has found that the side of the planet facing the Sun is bombarded by the solar wind. Without a protective magnetic field, the solar wind blows lighter elements in the atmosphere—hydrogen, oxygen, water—out into space. Venus lost a good deal of its atmospheric water in this way.
But what about the surface water? And where did all the CO2 come from? As the Venus Express researchers say, we will have to put a lander on Venus to answer those questions.