Goals: The European Space Agency's Venus Express was designed to study the atmosphere of Venus, from the surface to the ionosphere. The mission reused the same design as ESA's Mars Express and spare parts from other deep space missions.
Accomplishments: After arriving at Venus in April 2006, Venus Express logged many firsts. One of the most significant findings were signs that Venus had been volcanically active in the last three million years -- suggesting the planet may still be geologically active.
The orbiter also made extensive meteorological maps of Venus, providing measurements of wind fields and temperatures and the chemical composition of the atmosphere. The spacecraft found a striking double-eyed atmospheric vortex that dominates the south pole. It detected water molecules escaping into space, found concrete evidence for lightning in the Venusian atmosphere and provided infrared glimpses of the hot surface.
Venus Express, after running out of propellant, ended its mission in December 2014.