news item on a design study being undertaken to evaluate the best way to build a 'tumbleweed rover' for Mars. As the name suggests, you drop something like a spherical cage onto Mars, equipped with surfaces to catch the breeze, your favorite sensors and cameras, and let the wind take it where it will.
It sounds wonderfully elegant, until you start to worry about the details. Topography is the most obvious problem - even the bounciest tumbleweed, with the occasional blast of stormy weather - is eventually going to get stuck, wedged, or dropped into a spot that traps it. A solution is of course to drop lots of tumbleweed rovers onto a planet like Mars - certainly an appealing picture, dozens or more sweeping across Elysium Mare in a great Terran invasion. However, it's not entirely clear whether the type of data you could accumulate from such a campaign would balance out the cost.
Another idea that has done the rounds is to have a long-duration solar powered glider or aircraft, or even airship. At high altitude, away from anything but the tallest mountains, and above much of the debilitating martian dust storms, such semi-autonomous craft could provide in-atmosphere monitoring of chemistry, weather, and potentially higher resolution surface imaging than space-based platforms. Unlike a surface rover, the light-delay time to Earth would be less of an issue. Setting the airborne machine on a course for hundreds of miles could be done without the need for constant guidance. Similar ideas have also cropped up for exploring a far more alien environment on Titan. With a frigid but much thicker atmosphere, Titan could be a fantastic place for aerial exploration. With about a 90 minute light travel time - depending on the Earth-Saturn configuration - this may be the only real way to explore without a highly sophisticated AI calling the shots.
Many of these ideas take their inspiration from nature. The only question mark for me is that exploration or migration strategies used by organisms - be they bacteria or humans - may be optimal for survival or resource gathering, but not necessarily for gathering the best data.