March 25, 2013
Europe-Sized Storm On Venus Monitored By Astronomers Via ESA Spacecraft
Lee Rannals for redOrbit.com — Your Universe Online
Astronomers writing in the journal Nature Geoscience say they have been closely monitoring the movement of a huge whirlwind the size of Europe on Venus.
Researchers from Universidad del Pais Vasco (UPV) used an instrument on board the European Space Agency's (ESA) Venus Express spacecraft to monitor the evolution of the south pole vortex. The team monitored the movement of the vortex on two separate main cloud levels in Venus' atmosphere and was able to confirm the movement of the giant storm.
“We knew it was a long-term vortex; we also knew that it changes shape every day. But we thought that the centers of the vortex at different altitudes formed only a single tube, but that is not so. Each centre goes its own way, yet the global structure of the atmospheric vortex does not disintegrate," explains Itziar Garate-Lopez, head researcher and member of the UPV/EHU's Planetary Science Group.
The researchers said the centers of rotation in the upper and lower vortex rarely coincide in their position, forming a constantly evolving permanent structure on the surface of Venus. The planet has permanent vortices in its atmosphere at both poles, which is not uncommon for planets in our Solar System. Both Jupiter and Saturn are known for having long-term vortices in their atmospheres, but they are fast rotating planets while Venus rotates slowly. However, the rotation speed of Venus' atmosphere is greater than that of the planet.
“We´ve known for a long time that the atmosphere of Venus rotates 60 times faster than the planet itself, but we didn´t know why," said Garate-Lopez. "The difference is huge; that is why it´s called super-rotation. And we℠ve no idea how it started or how it keeps going.”
She said the seasonal effects and temperature differences on Earth between the continental zones and oceans create suitable conditions for the formation and dispersal of polar vortices. However, on Venus, there are no oceans or seasons, so the polar atmosphere behaves differently than our planet.
Venus Express' orbit was able to help the researchers get close to the North Pole and South Pole, providing the perfect view for the study.
"This is what we needed for our study, a more complete view of the vortex and at a lower speed, so that the instrument we used could capture the images we needed," Garate-Lopez said. "Also needed was a more extended view offering a detailed view of the planet's south pole, whereas the north pole is observed from much shorter distances, which prevents it from being observed globally," explains Garate-Lopez.
The team used Venus Express' VIRTIS-M infrared camera and analyzed data obtained in the course of 169 earth days. They also studied the data on the 25 most representative orbits.
"This camera doesn´t take individual photos like an ordinary camera, it divides the light into different wave lengths that enable various vertical layers of the planet´s atmosphere to be observed simultaneously. Besides, we have compared images separated by one-hour intervals and this has enabled us to monitor the speed at which the clouds move," says Garate-Lopez.
Last year, Venus made a transit between Earth and the Sun, allowing scientists an opportunity to view the planet in a new way and gather plenty of data through an event that will not take place again until 2117. Astronomers used the unique opportunity to study the atmosphere of Venus as it bent sunlight towards Earth. This not only helps scientists know more about Venus, but also know more about other planets orbiting other stars.
Scientists will be using data from this transit along with that collected from Venus Express to really hone in what we know about Earth's "twin."