The small Franco-German robot has just arrived on the asteroid Ryugu. Its lifetime, after a four-year journey, will be about fifteen hours.
In space, 325 million kilometers from Earth, no one heard the Mascot landing gear, dropped by the Japanese Hayabusa-2 probe, touch the surface of the asteroid Ryugu after a 51-meter freefall in the early hours of Wednesday, October 3.
Even if the small Franco-German machine – which has a mass of 10 kg and the dimensions of a large shoe box – has no system to stop its descent, even if Ryugu’s ground is only pebbles and roughness, everything went smoothly. The force of gravity exerted by this 900-meter diameter asteroid is so low that Mascot’s fall lasted several minutes. At the end of this step, what is a little difficult to name an impact occurred at about 0.5 km/h, just a little faster than the speed of a walking turtle.
“Mystery and danger.”
Then you have to imagine a scene that goes past the most sluggish of slow motion.
After its contact with the ground, Mascot, which lacked an anchoring system, went back upwards, starting a series of slow bounces. As explained, before landing, calculations predicted that the rebound phase could last a maximum of 105 minutes. According to the initial information provided by the DLR, the German space agency, this phase finally took only a few minutes.
At 7:36 am (Europe time), Mascot’s Twitter account sent this message: « And then I found myself in a place like no other on Earth, a region full of wonders, mystery, and danger! »
The end of the tumbles was not intended to mark the end of the landing itself. It was also necessary that the big dice that Mascot constituted placed itself on the right side, the one that allowed his instruments to work. The designers of the device, therefore, added a kind of arm with a weight to it to change faces.
Once correctly positioned, the lander, which has only about fifteen hours of autonomy, had to start harvesting scientific data using the four instruments that equip it, the main one being the French spectrometer.
The idea is to gather the maximum information about Ryugu, to get a relatively accurate picture of his soil, to prepare the sample collections that Hayabusa-2 will make; the first will take place at the end of October.
We should have to note that scientists designed Mascot as a scout, in the service of the Japanese probe. The principal objective of the mission is to bring back to Earth, at the end of 2020, a few tiny samples from the asteroid. Their analysis will help astronomers understand the composition of the Early Solar System, of which this type of body is a perfect representative.