After spending eight years in orbit, the Venus Express spacecraft is preparing to plunge deeper into the rocky planet’s atmosphere than ever before attempted. If it survives the daring maneuver planned for this summer, it’ll provide a view of an previously inaccessible region of the hostile Venusian atmosphere.
The European Space Agency’s Venus probe was launched on a Soyuz–Fregat rocket from the Russian Baikonur Cosmodrome in Kazakhstan in November 2005, arriving at Venus in April 2006. Since then, it’s been orbiting the planet in an elliptical 24-hour loop: from 66,000 kilometers over the south pole to 250 km above the north pole. Equipped with seven instruments for collecting data on the ionosphere, atmosphere, and surface of Venus, the spacecraft has been helping scientists understand how the planet has changed since it formed 4.6 million years ago.
“This information is helping us decipher how Earth and Venus came to lead such dramatically different lives, but we’ve also noticed that there are some fundamental similarities,” ESA’s Håkan Svedhem says in a news release. The two planets are about the same size and formed at right about the same time. But Venus has a surface temperature of 450 degrees Celsius, and its atmosphere is an extremely dense, “choking” mixture of noxious gases.
Infrared surveys of the chemical composition suggest that Venus may have had a plate tectonics system and an ocean of water like Earth. Right now, Earth has 100,000 times more water than Venus. But like our planet, Venus is losing parts of its upper atmosphere to space: There are twice as many hydrogen atoms escaping than oxygen, measurements from Venus Express show, suggesting how water is being broken up in the atmosphere.
Meanwhile, the spacecraft’s cameras have tracked thousands of features in the cloud tops some 70 km above the planet’s surface, including: an enormous swirling vortex at the south pole (which shares similarities with hurricanes on Earth) and bursts of lightning generated in clouds of sulfuric acid.
Venus Express also turned up hints of geological activity. Lava flows may have been created no more than 2.5 million years ago (that’s basically yesterday on the geologic timescale). Large variations in sulfur dioxide measurements in the upper atmosphere support the idea of present-day active volcanism. Additionally, Venus also has a “super-rotating” atmosphere that whips around the planet in four days (Earth days, to be specific). That’s much faster than the 243 days the planet takes to complete one rotation about its axis. However, scientists still aren’t sure whether there’s a relationship between increasing wind speeds and rotation.
Well, eight years later, fuel supplies are low, and Venus Express is preparing for its final mission: a controlled plunge deeper into the atmosphere than ever before attempted. In a daring, fuel-saving maneuver called “aerobraking” (visualized below) Venus Express will orbit at an altitude of 130 km from June 18 to July 11. During this time, it’ll make measurements with its magnetic field, solar wind, and atom analyzing instruments, as well as its temperature and pressure sensors. If the craft survives, the elevation of its orbit will be raised up to 450 km, and it might continue limited operations for a few more months, fuel permitting.
Top image: ESA/VIRTIS-VenusX IASF-INAF, Observatoire de Paris (R.Hueso, Univ. Bilbao)
Bottom image: ESA–C. Carreau