ESA Venus Express: Venus Dried Out Because It's Closer to Sun

This false-colour image of cloud features seen on Venus by the Venus Monitoring Camera (VMC) on the European Space Agency's Venus Express.

The image was captured from a distance of 30 000 km on 8 December 2011. 

ESA Venus Express has been in orbit around the planet since 2006.

CREDIT: ESA/MPS/DLR/IDA

Taking a closer look at the history of Venus, including how the planet transformed into a hellish hot house, may help astronomers predict the evolution of alien worlds, scientists say.

Ultraviolet rays from the sun sapped Venus' atmosphere of water during the planet's evolution, keeping it in a "prolonged molten state" for longer than Earth's molten state, a team of Japanese scientists has found.

Venus' vastly different environment came because it formed closer to the sun than Earth did, the researchers said.

With alien planets now a planetary-science frontier, studying Venus — which is within easy reach of Earth — will give clues about what to look for in exoplanet surfaces, they added.

"In a situation such [that] a magma ocean sustains very long, the planets are covered with a thick atmosphere.

Therefore, unfortunately, it would be difficult to observe their surface temperatures directly," said Keiko Hamano, a planetary scientist with Tokyo University who led the research.

"According to previous studies, however," he added, "hot atmospheres could contain unique species, such as alkali- and halogen-bearing gases. So, we hope to recognize hot surfaces indirectly by detecting their signatures on future missions."