Extremely Rare Venus Transit May Help Future Missions to Nearby Planet

Scientists have learned a bit more about Venus by examining a very rare transit. They watched Venus when it passed between Earth and the sun in order to make measurements of how the Venusian atmosphere absorbs different kinds of light.

Transits of Venus are so rare that they only happen twice in a lifetime. Every 115 years or so, Venus will appear to cross over the face of our home star twice, with eight years passing between the pair of transits. This phenomenon is not only incredible to watch, but also provides a unique opportunity for scientific observations of Venus.

In this case, astronomers took pictures of the entire even in several wavelengths of light. A team of scientists then used the picture to watch the backlit planet as it crossed in front of the sun. By observing the planet's atmosphere in different wavelengths of light during its journey, they learned more about what kinds of atoms and molecules are actually in its atmosphere.

"Radiation goes into the atmosphere and is absorbed, creating ions and a layer of the atmosphere called the ionosphere," said Dean Pesnell, one of the researchers, in a news release.

Because various types of atoms absorb light slightly differently, the height of this light absorption lets scientists know how many and what types of molecules make up Venus's atmosphere. This information is important for planning missions to Venus.

"The planet appeared very round in all wavelengths," said Pesnell. "If the transitions from day to night were different from the transition from night to day, you would expect a bulge in the atmosphere on one side of the planet."

The findings could help with future space missions. In addition, it reveals that there aren't any drastic changes from day to night in Venus's atmosphere.

The findings are published in the journal Nature Communications.

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