NASA already has robots exploring the surface of Mars, but there are plenty of places these roaming science laboratories cannot go. One day a pint-sized rover may help fill in the blanks, with the space agency developing a flat-packed, shape-shifting two-wheeler that can not only handle rougher terrain, but can squeeze into confined spaces where organic molecules may be waiting to be discovered.
The Puffer robot was inspired by origami and started out as a paper robot with four wheels. The researchers then swapped the paper material being used as the robot's main body for a printed circuit board, which allowed them to incorporate electronics. They also cut the number of wheels to two and fitted them with treads so they could handle inclines.
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These wheels also fold inwards, which reduces Puffer to the size of a smartphone and allows a number of them to be stacked on top of one another for easier transport. But this compact configuration comes in handy when Puffer is on the move too, as it can still move forward and crawl into tight spaces beneath ledges, or drop into pits or craters.
Puffer also has a so-called "skittering walk" mode, which allows it to move forward slowly one wheel at a time without slipping. This means the robot can walk up steep inclines even on surfaces that don't provide great traction. It also features a tail for extra stability and solar panels on its belly, allowing it to flip over when it needs a recharge.
On flat ground in its current form, Puffer can travel around 2,050 ft (625 m) on each charge. It is already equipped with a micro-imager that allows it to see objects just 10 microns in size, but the team aims to kit it out with more scientific instruments, such as a spectrometer to study chemistry or technologies to sample water for organic material.
Future upgrades would also include making it autonomous, making it more robust by scaling it up and, one day, deploying it on other planets for exploratory missions. The team has tested the robot on the active volcano Mt Erebus in Antarctica, across rocky terrain in Rainbow Basin, California and at a ski resort in Colorado, showing off its ability to handle snowy environments.
The Rainbow Basin tests in particular offer a taste of what Puffer could get up to on Mars, as it scooted over rocky slopes and under overhangs. On the Red Planet, these kinds of overhangs could be hiding organic molecules from harmful radiation, while the dark Martian slopes are another area scientists would like to learn more about but can't access with current rovers.
One thing Puffer already has in its favor is that the materials used have been tested in earlier space missions, this includes Nomex, the textile used in the airbags that softened the fall for the Spirit and Opportunity rovers when they touched down on Mars.
"Small robotic explorers like Puffer could change the way we do science on Mars," Karras said. "Like Sojourner before it, we think it's an exciting advance in robotic design."
You can see Puffer adjust its shape to access tight areas in the video below.