The Venus Express probe from the European Space Agency (ESA) was terminated in December of 2014 in Venus’ atmosphere after its mission had been completed. Researchers have now revealed some of the data gathered from the probe’s plunge into the atmosphere and the results are truly interesting.
The probe began its adventure into Venus’ atmosphere in June of 2014. It had been launched back in November of 2005 and by the time it reached Venus, it was close to the end of its mission in space. It did not have much fuel left but scientists decided to make best of what opportunity they were given to explore Venus, especially its poles and upper atmosphere. Their findings have recently been published in Nature Physics, a scientific journal.
"None of Venus Express' instruments were actually designed to make such in-situ atmosphere observations,” said the article’s lead author Ingo Müller-Wodarg of Imperial College London, UK. “We only realized in 2006 – after launch! – that we could use the Venus Express spacecraft as a whole to do more science."
What’s interesting is that the findings show that many parts of Venus are actually a lot colder than had been expected. Venus’ temperatures can reach highs of 460°C (860°F) on the surface, making it the hottest planet in the Solar System. Additionally, it possesses one of the thickest atmospheres which traps the heat. But the Venus Express probe, traveling at an altitude of 130 to 140 kilometers (81 to 87 miles) above the surface showed that Venus’ poles are actually much colder than Earth’s. The polar atmosphere of Venus is -157°C (-251°F), a difference of 70 degrees from prior belief. In addition, the atmosphere is 22 to 40 percent less dense than what was previously thought.
"These lower densities could be at least partly due to Venus' polar vortices, which are strong wind systems sitting near the planet's poles,” said Müller-Wodarg. “Atmospheric winds may be making the density structure both more complicated and more interesting!"
Something else discovered was that the polar region of Venus possesses something known as atmospheric gravity waves, which are ripples in the atmosphere that travel from low to high altitudes, vertically, as density of the atmosphere decreases. (They actually have nothing to do with actual gravity.) The Venus Express discovered that the atmospheric waves originate about 90 kilometers (56 miles) above the surface in Venus’ upper cloud layer. Planetary waves are also present, which are larger atmospheric waves that are caused by the planet’s rotation.
To make these findings, Venus Express was required to perform aerobraking maneuvers, using the Venusian atmosphere to slow the spacecraft’s velocity. And this maneuver could have implications for the European Trace Gas Orbiter, currently on its way to Mars, which will use a similar technique to measure the composition of various gases in the Martian atmosphere.
Venus Express may have died a fiery death more than a year ago, but results from the mission are still turning up some surprises. And with Japan’s Akatsuki mission recently beginning its own science mission around Venus, it's clear there is still much to learn about the second planet from the Sun.