Venus Express Detects Water Vapour in Low Altitude Clouds

There’s a real advantage to having a spacecraft orbit a planet for days, months and even years. You have lots and lots of time to really pull in the science. And now, almost 2 years into its visit at our evil twin planet, ESA’s Venus Express has been able to map the planet’s atmosphere at lower altitudes, searching for chemicals that will help scientists understand the planet’s global climate and weather systems.

The planet’s clouds block the visible light from escaping the surface, but other wavelengths, such as infrared, do escape. Since temperatures can reach 200 degrees C at an altitude of 35 km, and more than 450 C at the surface, infrared – or heat – pours out, going right through the clouds. This radiation can then be analyzed to see the chemicals present.

ESA’s Venus Express spacecraft is equipped with a special instrument called the VIRTIS spectrometer, which can measure the atmosphere at various altitudes. It’s already mapped the high altitude clouds, and now VIRTIS has spent the last few orbits mapping the lower atmosphere.

Of course, like the rest of Venus’ atmosphere, the lower altitude clouds are dominated by carbon dioxide – the greenhouse gas that traps the heat in, raising temperatures. VIRTIS also detected carbon monoxide, a chemical that scientists weren’t expecting to see at such low altitudes.

Since carbon monoxide is so rare, scientists can use this as a way to trace global winds that cycle across the planet – sort of like dropping ink into water to study turbulence. VIRTIS was able to determine the large-scale circulation of winds as they rise at the equator and then move north and south towards the poles. Once at the poles, the winds lose altitude again, and circulate back to the beginning.

Venus Express has also detected and mapped the amount of water vapour in the lower atmosphere with high resolution. Since this molecule is so difficult to detect, this has ended a scientific debate about how much there is on Venus.

Original Source: ESA News Release