One engineer is working on what amounts to a nanobot Mars base, which would protect the 'bots from cosmic radiation.For more complex and directed missions, such as digging under Mars's surface and collecting samples, robots will have to move autonomously and under their own power. Researchers at NASA's ANTS (Autonomous Nanotechnological Swarm) program have been developing concepts for tiny robots, called TETwalkers, capable of doing just that. Each TETwalker would be a tetrahedron of carbon-nanotube struts connected by joints. Each individual robot could move by lengthening or shortening its struts, thereby shifting its center of gravity until it tumbles in the desired direction. Together, tens of thousands of nanoscale TETwalkers could connect together to form devices such as rovers and antennas, which could travel the planet in search of signs of life and water. So far, engineers have built a two-foot-high proof-of-concept that moves in response to human commands. To shrink this prototype to nanoscale, scientists need advanced nanotubes that can both move themselves and rearrange themselves to form different kinds of materials. Program head Steve Curtis says that depending on the speed of nanotech development and funding levels, TETwalkers could land on Mars within the next 30 to 40 years.