A balloon-shaped robot explorer that one day could search for evidence that water existed on other planets has survived some of the most trying conditions on planet Earth during a 70-kilometer (40-mile), wind-driven trek across Antarctica.

The tumbleweed rover, which is being developed at NASA's Jet Propulsion Laboratory in Pasadena, Calif., left the National Science Foundation's Amundsen-Scott South Pole Station on Jan. 24, and spent the next eight days rolling across Antarctica's polar plateau.

Tumbleweed rover in Antarctica. Credit: NASA/JPL

Along the way, the beach ball shaped device, roughly six feet in diameter, used the global Iridium satellite network to send information on its position, the surrounding air temperature, pressure, humidity, and light intensity to a ground station at JPL.

The test was designed to confirm the rover's long-term durability in an extremely cold environment, with an eye toward eventually using the devices to explore the martian polar caps and other planets in the solar system.

The final tumbleweed rover is envisioned as a lightweight, roughly 88-pound device that can serve multiple roles as an independent robotic explorer. The rover's design can allow it to act in turn as a parachute while descending through an atmosphere; an air bag on landing; and, ultimately, as an unmanned vehicle equipped with a package of scientific instruments.

The tumbleweed rover is based on concepts going back to the 1970's and has been pursued by several investigators at JPL. Dr. Alberto Behar, a robotics researcher in the robotic vehicles group recently deployed this prototype at the South Pole. "We are testing a new mode of rover transportation that uses the available environmental resources to give us an added edge to cover more ground using fewer on-board resources," said Dr. Behar. "This gives us the ability to use the precious cargo (on Earth) or payload (in space) mass for more applicable science instrumentation."

Even though the average external temperature during the rover's deployment was recorded to be on average -30 degrees Celsius or -22 degrees Fahrenheit, the rover kept its internal instrument payload at an average temperature of roughly 30 degrees Celsius or 86 degrees Fahrenheit. The rover was able to stay warm by self-heating due to running electronics and an internal air pump.

The ultra-durable ball reached speeds of 16 kilometers per hour (10 miles per hour) over the Antarctic ice cap, and traveled at an average speed of about 6 kilometers per hour (3.7 miles per hour). The winds at the South Pole were unusually low during the test. As a result, there were several periods during its deployment when the rover did not move at all. Even taking those lulls into account, the rover managed an average speed of 1.3 kilometers per hour (.8 miles per hour) over the course of the deployment.

Behar said the rover's design is especially well suited for polar missions to use instrument packages to look for water beneath a surface desert or an ice sheet, a task that cannot be done accurately from orbit.

Plans to construct the next generation tumbleweed rover are already underway at JPL.  Future refinements of the design are likely to focus on reducing the rover's weight and rolling resistance to reduce the minimum winds needed to enable it to travel farther and the adaptation of the payload to include a ground-penetrating radar to conduct terrain and ice surveys.

Behar says he hopes an updated version of the rover will be deployed again later this year, and the design may one day find itself rolling on the polar icecaps of Mars.

The tumbleweed rover project is managed by NASA's Jet Propulsion Laboratory and was supported jointly by NASA's Office of Space Science, Washington, D.C. and the National Science Foundation.