Venus May Actually Be Cold Enough For Snow
October 1, 2012

Venus Hosts Curious Cold Layer In Atmosphere

Lee Rannals for - Your Universe Online

The European Space Agency said on Monday that Venus Express has spotted an area of Venus that may be cold enough to produce carbon dioxide snow.

Venus is known for its thick, carbon dioxide atmosphere, but also its hot surface. Due to its size, it is often referred to as Earth's twin, despite not having the life-giving features Earth provides.

In a new analysis based on five years of Venus Express observations, scientists have uncovered a chilly area on Venus, boasting temperatures of around -283 degrees Fahrenheit.

This cold location is in the atmosphere 77 miles above the planet's surface, and the chilly layer is far frostier than any of Earth's atmosphere.

Scientists made the discovery while watching as light from the Sun filtered through the atmosphere to reveal the concentration of carbon dioxide gas molecules at various altitudes along the terminator, which is the dividing line between the day and night sides of the planet.

The scientists used information about the concentration of carbon dioxide and combined it with data on atmospheric pressure at each height to calculate the corresponding temperatures.

“Since the temperature at some heights dips below the freezing temperature of carbon dioxide, we suspect that carbon dioxide ice might form there,” said Arnaud Mahieux of the Belgian Institute for Space Aeronomy and lead author of the paper published in the Journal of Geophysical Research.

Astronomers also know if small carbon dioxide clouds are made up of ice or snow particles because they should be reflective, leading to brighter than normal sunlight layers in the atmosphere.

“However, although Venus Express indeed occasionally observes very bright regions in the Venusian atmosphere that could be explained by ice, they could also be caused by other atmospheric disturbances, so we need to be cautious,” Mahieux said.

The study found that the cold layer at the terminator is sandwiched between two comparatively warmer layers.

“The temperature profiles on the hot dayside and cool night side at altitudes above 120 km (74 miles) are extremely different, so at the terminator we are in a regime of transition with effects coming from both sides," said Mahieux. “The night side may be playing a greater role at one given altitude and the dayside might be playing a larger role at other altitudes.”

ESA said similar temperature profiles along the terminator have been derived from other Venus Express datasets, such as measurements taken during the 2012 transit of Venus.

Models can predict the observed profiles, but further confirmation will be provided by examining the role played by other atmospheric species, like carbon monoxides, nitrogen and oxygen.

“The finding is very new and we still need to think about and understand what the implications will be,” HÃ¥kan Svedhem, ESA´s Venus Express project scientist, said. “But it is special, as we do not see a similar temperature profile along the terminator in the atmospheres of Earth or Mars, which have different chemical compositions and temperature conditions.”