ESA Venus Express unravels mysteries of the shrouded planet

Venus is sometimes referred to as Earth's sister planet. It has an atmosphere and a weather system, and it is of similar size and density to our own planet.

However it is the Venusian atmosphere that is the most striking contrast between the two planets.

The thick, choking clouds trap heat on the planet, causing the surface temperature to reach an average 465 degrees Celsius.

The atmosphere also makes studies of Venus difficult, as it shields the surface from view.

The first scientific studies of Venus from orbit were performed during a flyby in 1962 by Mariner 2. Other craft have also attempted to peer through the haze of Venus, such as the Russian Venera orbiters and landers.

Unlike Mars, where rovers can roam the surface for years, the Venera landers lasted no longer than 2 hours due to the crushing surface pressure of 90 bar.

The latest era of Venusian exploration is being performed courtesy of the European Space Agency's Venus Express (VEX).

Venus Express was launched on 9 November 2005 aboard a Soyuz-Fregat rocket from the Baikonur Cosmodrome in Kazakhstan.

VEX entered orbit around Venus on 11 April 2006.

The mission was designed to last four days – Venusian days that is. Venus rotates very slowly, so one rotation of Venus is equivalent to 243 days on Earth.

The mission has been extended until 2014, pending a review later this year to prove that the craft is still in a good working condition.

The mission extension will see VEX continue to study the atmosphere of Venus in order to seek out any long term trends present, as well as monitor the planet during the peak of the solar cycle.

Venus Express reuses parts of the Mars Express design, such as the structural design, propulsion system and the use of dual solar arrays.

However VEX receives four times more radiation than Mars Express, so it has been modified to account for this, such as being gold instead of black to reflect the Sun's radiation.

VEX set out with a lengthy list of questions to answer about our mysterious “sister planet”, such as seeking out seismic activity, finding what drives the atmospheric escape, learning about the speedy winds and atmospheric rotation, and discovering how the cloud system works.

“Venus Express has successfully achieved almost all science goals stated in the mission proposal 10 years ago,” says ESA's Dmitrij Titov.

“I think the major result of VEX is that the mission has provided a comprehensive survey of the Venus atmosphere and plasma environment over the period of 6 years. Is there anything left to do? Yes. Observations of such a complex system as the Venus atmosphere require as long as possible extension, that would help to study its long term behaviour.”

Six years after entering orbit around Venus, around 250 scientific papers using results from VEX have been published detailing many of the discoveries by the orbiter. VEX uses seven scientific instruments to survey the planet and learn about why it became such a hostile environment.

The Analyser of Space Plasma and Energetic Atoms (ASPERA) instrument keeps a watchful eye on particles escaping Venus' atmosphere, and this data has allowed astronomers to calculate the escape rates of hydrogen, helium, and oxygen.

Studies have revealed that Earth loses more of its atmosphere to space than Venus does, yet it was thought that the Earth’s magnetic field would offer more protection compared to a planet that only has a weak induced magnetic field.

The magnetic field on Venus is caused by the solar wind interacting with the planet’s atmosphere, and the field is measured by the Venus Express Magnetometer (MAG).

Venus Express unravels mysteries of the shrouded planet