Archimedes is the project of the German Mars Society of a Mars Balloon probe carrying a scientific payload and entering the Mars atmosphere in a fully inflated configuration. The probe would be transported to Mars onboard a satellite around 2020.
The project started in 2001. In 2008 a downscaled model of Archimedes has been tested during a sounding rocket campaign in Northern Sweden. Another flight test is under preparation for 2014.
MORE INFORMATION HERE