Hopping Robots Free Fall To The Surface Of Asteroid Ryugu

UPDATE Sept. 22 — This photo was taken by MINERVA Rover-1B shortly after it separated from the spacecraft. The haziness at left is sunlight scattered by the camera’s optics. JAXA
This photo, taken as the MINERVA hoppers floated down to the surface of the asteroid, was taken from an altitude of just 262 feet (80 meters) above its surface last night. The shadow of the spacecraft, Hayabusa-2, is visible at left. JAXA

It’s happening right now. Two little robots bristling with sensors and cameras departed the Japanese spacecraft Hayabusa-2 at 11:06 p.m. yesterday and have begun their free-fall descent to the surface of Ryugu, a barren, rocky asteroid 0.6 miles (1 km) across some 200 million miles (322 million km) from Earth. Named MINERVA II-1A and MINERVA II-1B, they’ll land on the asteroid and explore its surface via a unique form of propulsion — hopping.

One of the MINERVA’s will break down into two smaller rovers for a total of three (for now) bouncing around the asteroid. Rover 1A and 1B are just 7 inches wide and 2.8 inches (18×7 cm) tall. JAXA

Being small, Ryugu has a very low surface gravity. If the Minervas (stands for Micro Nano Experimental Robot Vehicle for Asteroid) tried to move using wheels or treads, the push-back would launch the probes off the surface and into space. Instead, an internal rotating motor will make each rover hop from place to place. During each hop, the MINERVAs are expected to remain airborne for up to 15 minutes and move up to 50 feet (15-meters) horizontally across the surface. Picture a rabbit (about the same size as a MINERVA) taking a leap, tumbling and turning above the ground for 15 minutes before finally landing again in a new spot.

This is an artist’s illustration of the three hopping rovers on Ryuku’s surface with MINERVA-II1A and MINERVA-II1B (left and center), and MINERVA-II2 (right) exploring the surface of the asteroid Ryugu. JAXA

What we learn from the MINERVAs will provide pictures and context for the samples that will be picked up by the main spacecraft next year and returned to Earth in December 2020.

Stay in touch with the latest news about the spacecraft and the MINERVAs via Twitter.