Good search terms for this would be "mars aerobot". This turns up lots of good links for LTA (lighter than air) mission concepts, and a couple of offhand menti

Good search terms for this would be "mars aerobot". This turns up lots of good links for LTA (lighter than air) mission concepts, and a couple of offhand mentions of HTA concepts. These are all separate from the ARES concept that is already linked nearby. Here's some examples: [a long time ago, but serious] http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/17308/1/99-0751.pdf http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/17308/1/99... [Venus, or maybe Titan] http://www.astrobio.net/news-exclusive/up-up-and-away-with-aerobots/ http://www.astrobio.net/news-exclusive/up-up-and-away-with-a... [Mars, with Earth demo] http://robotics.estec.esa.int/i-SAIRAS/isairas2005/session_10b/3_behar_10b.pdf http://robotics.estec.esa.int/i-SAIRAS/isairas2005/session_1... I learned that the Soviet Union used two small balloons to explore Venus in 1985. edited to add: I noticed a comprehensive design study for ARES which covers a lot of reasoning for tradeoffs: http://www.cs.odu.edu/~mln/ltrs-pdfs/NASA-aiaa-2003-6578.pdf http://www.cs.odu.edu/~mln/ltrs-pdfs/NASA-aiaa-2003-6578.pdf