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Two small Japanese rovers have begun to explore the surface of the large Ryugu asteroid over the weekend – but they are not traveling in the traditional sense of the word.
The small robots, called MINERVA-II1A and MINERVA-II1B, landed on Friday morning (21 September) after separating from their tanker Hayabusa2, which is orbiting the 900-meter-high Ryugu since the end of June.
MINERVA-II1A and MINERVA-II1B do not have wheels as do the rovers of NASA's opportunity and curiosity – and there's a very good reason for that. [Japan’s Hayabusa2 Asteroid Ryugu Mission in Pictures]
"The gravity on the surface of Ryugu is very low, so a vehicle powered by normal wheels or crawlers would float up as soon as it started to move," wrote officials at the Japanese Agency. aerospace exploration (JAXA). and MINERVA-II1B.
So the robots – each one measures 7 inches wide by 2.8 inches tall (18 by 7 centimeters) and weighs 2.4 pounds. (1.1 kg) – jump instead. They do this by moving a "torquer" into their interior, which rests on a disk-shaped turntable.
"By rotating the torch, a reaction force against the surface of the asteroid makes the mobile have a high horizontal velocity," wrote a team of researchers led by Tetsuo Yoshimitsu of JAXA in 2012. "After hopp[ing] in free space, it moves in a ballistic manner. With this mechanism, by changing the amplitude of the torque, the jump speed can be changed so as not to exceed … the speed of escape of the surface of the asteroid. "
MINERVA-II1 rovers control the direction of their hops by manipulating platinum orientation, the scientists added. These jumps can last 15 minutes and cover about 15 meters (50 feet) of horizontal distance. And rovers are designed to make their exploration decisions independently, without orientation of the Earth.
A close look at the MINERVA-II1 vehicles of the Japanese Aerospace Exploration Agency delivered to the Ryugu asteroid by the spacecraft Hayabusa2 in September 2018. Rover-1A is on the left, with Rover-1B to the right. Back is the blanket in which they were stored.
Credit: JAXA
This mobility system was not invented from scratch for the Hayabusa2 mission. The same basic idea was incorporated into the original MINERVA hopper, which flew on JAXA's first Hayabusa spacecraft. This mission came into orbit around the rock asteroid Itokawa in 2005 and was able to return small grains from the surface of the rock to Earth five years later. But MINERVA has not managed to land on Itokawa. (And, in case you're wondering, MINERVA stands for "Micro Nano Experimental Robot Vehicle for Asteroid.")
Other landings from Ryugu will be arriving soon, if everything goes as planned. Hayabusa2 is carrying another bantam hopper called MINERVA-II2, as well as the MASCOT lander ("Mobile Asteroid Surface Scout"), built by the German space agency DLR, in collaboration with CNES. [Asteroid Basics: A Space Rock Quiz]
The 22 lbs (10 kg) MASCOT, which carries four scientific instruments, is expected to land on Ryugu on 3 October. Despite its designation "lander", MASCOT will be mobile and evolve in a similar way to that of MINERVA-II1. duo.
This photo was captured by the Minerva-II1A rover during a jump after she managed to land on the asteroid Ryugu on September 21, 2018.
Credit: Japan Aerospace Exploration Agency
The MASCOT system "includes a tungsten swingarm, accelerated and decelerated by a motor, that tilts the entire system, allowing MASCOT to move by" jumping "and moving to the position required to conduct the experiments." DLR officials wrote in a description of MASCOT.
This swingarm is located inside MASCOT, just as the MINERVA-II1 pistons are inside these small hoppers. The MASCOT system will allow the LG to straighten as needed and jump up to 70 meters (230 feet) from one location to another, said DLR officials.
MINERVA-II2, meanwhile, is a surprisingly complex beast. This small hopper, developed by a consortium of Japanese universities, integrates four different mobility systems in its 2.2 pounds. (1 kg): an "environment-dependent buckling mechanism", a "leaf spring buckling mechanism", a "motor-driven eccentric micropack mechanism" and "a permanent mechanism for the generation of buckling springs"; impact, "according to a Hayabusa Information Sheet2.
MINERVA-II2 is an "optional" mobile, indicates this card. So, it is not clear for now if and when the rover will be heading towards the Ryugu surface.
The $ 150 million Hayabusa2 mission was launched in December 2014. Its main objectives are to shed light on the beginnings of the solar system and the role played by carbon-rich asteroids such as Ryugu in helping life on Earth.
In addition to obtaining all the data collected by the mother ship and the surface craft from the asteroid, Hayabusa2 aims to return a sample of raw Ryugu material to Earth. If all goes as planned, this cosmic land and rock should hit the parachute in Australia in December 2020.
NASA has its own mission of sampling asteroids in progress. The OSIRIS-REx probe from the US Space Agency is expected to orbit the carbon-rich asteroid Bennu on December 31 and return samples of the rock-space in September 2023.
Follow Mike Wall on Twitter @ michaeldwall and Google+. follow us @Spacedotcom, Facebook or Google+. Originally posted on Space.com.
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