‘Hedgehog’ robots could shed light on origins of Mars moon

Spherical robots covered in spikes could be used to explore the surface of Mars’s moons, according to researchers in the US.

Scientists at Stanford University, the Massachusetts Institute of Technology (MIT) and NASA have designed the ‘hedgehog’ robots to roll across the cratered surface of the Martian moon Phobos, gathering and relaying information about its composition, and other data that could help to shed light on its origins.

The hedgehogs would be deployed from an orbiting mothership called the Phobos Surveyor, a coffee-table-sized vehicle flanked by two umbrella-shaped solar panels that would help the robots to determine their position and orientation in order to map their trajectories, and to relay their gathered data back to Earth.

Phobos could also be useful as a base for studying Mars and serve as a site to test technologies for use in a human mission to the planet because its gravity is much weaker than that of Mars and so costs and dangers would be reduced, said the robots’ developer Marco Pavone of Stanford’s Department of Aeronautics and Astronautics.

‘It’s a piece of technology that’s needed before any more expensive type of exploration is considered,’ he said in a statement. ‘Before sampling, we need to know where to land. We need to deploy rovers to acquire information about the surface.’

Instead of using wheels like traditional rovers, the hedgehogs exploit the low gravity of Phobos by moving with the use of three rotating discs inside each robot, each pointing in a different direction.

In the microgravity of Phobos, the inertial forces of the spinning discs cause the hedgehogs to jump if they are accelerated quickly or tumble across the surface if the area accelerated just slightly.

The Surveyor would deploy one hedgehog at a time with gaps of several days, using the data from each one to determine the next launch site.

The mothership would also take large-scale measurements of the moon’s surface, for example, using a gamma ray or a neutron detector to measure the concentration of various chemical elements and compounds.

Studying the origin of Phobos — which is thought to be an asteroid captured by the gravity of Mars or a piece of Mars that an asteroid impact flung into orbit — could help us to understand the creation of our own moon.

The platform could also be used to explore any of the Solar System’s smaller members, including comets and asteroids, said Pavone. ‘The bottom line is that there is a growing interest in the exploration of small bodies,’ he said.

The team has already built and tested two generations of rover prototypes and is developing a third. Although the third generation is cube shaped, future generations would be likely to have more sides, eventually becoming almost spherical.

The team has also developed a prototype Surveyor and hopes to test it in two to four years. Pavone hopes that a Phobos Surveyor mission could be carried out within the next 10–20 years.

The researchers initiated the spacecraft-rover project as part of the NASA Innovative Advanced Concepts Program. They will present a paper describing their platform’s proposed mission at the Institute of Electrical and Electronics Engineers Aerospace Conference in March.