The European Space Agency (ESA) is bidding a sad farewell to its trusty Venus Express probe as it slowly plunges into the hellish Venusian atmosphere, bringing its eight-year mission to a dramatic, fiery end. Full contact was lost with the craft last month after a series of exhausting manoeuvres drained its propellant, meaning ESA is no longer able to maintain its altitude. Although difficult to predict, ESA expects its life will end in spectacular style towards the end of January after being charred and crushed by intense pressure and heat.
But we shouldn’t be too disappointed; the Venus Express has gathered an overwhelming amount of scientific information and has far exceeded its anticipated two-year shelf life. The probe arrived at our neighbor planet back in 2006 after being launched the previous year, and quickly settled in to a 24-hour elliptical orbit. Since then, it had been dunking in and out of the planet’s thick, cloudy air, defiantly hoarding data for six years longer than originally intended.
However, earlier this year, the craft’s propellant started running low, so ESA decided to test out a daring, experimental manoeuvre called aerobraking. This saw the probe dip down to dangerously low altitudes, allowing ESA to gather data on previously unexplored regions of the atmosphere. At its lowest point, it was skimming the atmosphere at 130 kilometers above the surface.
ESA then raised its altitude to safer levels with a series of thruster burns, but unfortunately its lowest point of orbit began to gradually reduce again due to the planet’s gravity. Full communication was then lost at the end of last month, suggesting the raising manoeuvres burned up its remaining propellant. Without propellant, the craft can’t be oriented towards Earth to maintain contact, nor can its altitude be increased. Now clutched firmly by the planet’s gravitational grasp, the probe will continue to slowly dive through the atmosphere over the next month or so before eventually burning up.
Although it’s sad to have to wave goodbye to such a trooper, the probe truly outdid itself and revealed some fascinating secrets about the planet, which has been dubbed Earth’s “evil twin.” With crushing air pressures, surface temperatures of over 450oC and a choking, dense atmosphere of CO2 and toxic sulfuric acid clouds, Venus may seem worlds apart from Earth. But our neighbor is virtually identical in terms of size and mass, is composed of similar materials, and may have even once had a water-rich atmosphere like our own.
NASA, via Wikimedia Commons
Indeed, the Venus Express found some evidence to suggest that the now parched surface once sported water, possibly even oceans like those found on Earth. Furthermore, much like Earth, the probe discovered that part of the planet’s upper atmosphere is gradually being shed into space, and that water is being broken up in its atmosphere.
Another interesting finding was that the planet may still be geologically active as evidence of recent volcanic activity was gathered. Not only were lava flows spotted, which were likely created within the last 2 million years, but levels of atmospheric sulfur dioxide appeared to fluctuate throughout the mission, hinting at active volcanism.
ESA/ AOES. Artist's impression of an active volcano on Venus.