Numerous boulders, many rocks, no dust: MASCOT's zigzag course across the asteroid Ryugu

October 12, 2018, German Aerospace Center
MASCOT's approach to Ryugu and its path across the surface. Credit: German Aerospace Center

Six minutes of free fall, a gentle impact on the asteroid and then 11 minutes of rebounding until coming to rest. That is how, in the early hours of 3 October 2018, the journey of the MASCOT asteroid lander began on Asteroid Ryugu – a land full of wonder, mystery and challenges. Some 17 hours of scientific exploration followed this first 'stroll' on the almost 900-metre diameter asteroid. The lander was commanded and controlled from the MASCOT Control Centre at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) site in Cologne in the presence of scientific teams from Germany, France and Japan. MASCOT surpassed all expectations and performed its four experiments at several locations on the asteroid. Never before in the history of spaceflight has a Solar System body been explored in this way. It has now been possible to precisely trace MASCOT's path on Ryugu's surface on the basis of image data from the Japanese Hayabusa2 space probe and the lander's images and data.

"This success was possible thanks to state-of-the-art robotic technology, long-term planning and intensive international cooperation between the scientists and engineers of the three space nations Japan, France and Germany," says Hansjörg Dittus, DLR Executive Board Member for Space Research and Technology about this milestone in Solar System exploration. "We are proud of how MASCOT was able to master its way across the asteroid Ryugu over boulders and rocks and send so much data about its composition back to Earth," says DLR Chair Pascale Ehrenfreund.

MASCOT had no propulsion system and landed in free fall. Six minutes after separating from Hayabusa2, and following the end of a ballistic trajectory, the landing module made its first contact with asteroid Ryugu. On the surface, MASCOT moved through the activation of a tungsten swing arm accelerated and decelerated by a motor. This made it possible for MASCOT to be repositioned to the 'correct' side or even perform hops across the asteroid's surface. The gravitational attraction on Ryugu is just one 66,500th of the Earth's, so the little momentum provided was enough: a technological innovation for an unusual form of mobility on an asteroid surface used for the first time in the history of space travel as part of the Hayabusa2 mission.

Through a rock garden full of rough boulders and no flat surfaces

To reconstruct MASCOT's path across the surface of Ryugu, the cameras aboard the Hayabusa2 mother probe were aimed at the asteroid. The Optical Navigation Cameras (ONC) captured the lander's free fall in several images, detected its shadow on the ground during the flight phase, and finally identified MASCOT directly on the surface in several images. The pattern of the countless boulders distributed on the surface could also be seen in the direction of the respective horizon in oblique photographs of the lander's DLR MASCAM camera. The combination of this information unlocked the unique path traced by the lander.

After the first impact, MASCOT smoothly bounced off a large block, touched the ground about eight times, and then found itself in a resting position unfavourable for the measurements. After commanding and executing a specially prepared correction manoeuvre, MASCOT came to a second halt. The exact location of this second position is still being determined. There, the lander completed detailed measurements during one asteroid day and night. This was followed by a small 'mini-move' to provide the MicrOmega spectrometer with even better conditions for measuring the composition of the asteroid material.

Finally, MASCOT was set in motion one last time for a bigger jump. At the last location it carried out some more measurements before the third night on the asteroid began, and contact with Hayabusa2 was lost as the spaceship had moved out of line of sight. The last signal from MASCOT reached the mother probe at 21:04 CEST. The mission was over. "We were expecting less than 16 hours of battery life because of the cold night, says MASCOT project manager Tra-Mi Ho from the DLR Institute of Space Systems. "After all, we were able to operate MASCOT for more than one extra hour, even until the radio shadow began, which was a great success." During the mission, the team named MASCOT's landing site (MA-9) 'Alice's Wonderland', after the eponymous book by Lewis Carroll (1832-1898).

A true wonderland

Having reconstructed the events that took place on asteroid Ryugu, the scientists are now busy analysing the first results from the acquired data and images. "What we saw from a distance already gave us an idea of what it might look like on the surface," reports Ralf Jaumann from the DLR Institute of Planetary Research and scientific director of the MASCOT mission. "In fact, it is even crazier on the surface than expected. Everything is covered in rough blocks and strewn with boulders. How compact these blocks are and what they are composed of, we still do not know. But what was most surprising was that large accumulations of fine material are nowhere to be found – and we did not expect that. We have to investigate this in the next few weeks, because the cosmic weathering would actually have had to produce fine material," continues Jaumann.

"MASCOT has delivered exactly what we expected: an 'extension' of the space probe on the surface of Ryugu and direct measurements on site," says Tra-Mi Ho. Now there are measurements across the entire spectrum, from telescope light curves from Earth to remote sensing with Hayabusa2 through to the microscopic findings of MASCOT. "This will be of enormous importance for the characterisation of this class of asteroids," emphasises Jaumann.

Ryugu is a C-type asteroid – a carbon-rich representative of the oldest bodies of the four-and-a-half-billion year-old Solar System. It is a 'primordial' building block of planet formation, and one of 17,000 known Near-Earth asteroids.

On Earth, there are meteorites with a composition that could be similar to Ryugu's, which are found in the Murchison Range, Australia. However, Matthias Grott from the DLR Institute of Planetary Research and responsible for the radiometer experiment MARA is skeptical as to whether these meteorites are actually representative of Ryugu in terms of their physical properties: "Meteorites such as those found in Murchison are rather massive. However, our MARA data suggests the material on Ryugu is slightly more porous. The investigations are just beginning, but it is plausible to assume that small fragments of Ryugu would not survive the entry into the Earth's atmosphere intact."

About the Hayabusa2 mission and MASCOT

Hayabusa2 is a Japanese space agency (Japan Aerospace Exploration Agency; JAXA) mission to the near-Earth asteroid Ryugu. The German-French lander MASCOT on board Hayabusa2 was developed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and built in close cooperation with the French space agency CNES (Centre National d'Etudes Spatiales). DLR, the Institut d'Astrophysique Spatiale and the Technical University of Braunschweig have contributed the scientific experiments on board MASCOT. The MASCOT lander and its experiments are operated and controlled by DLR with support from CNES and in constant interaction with the Hayabusa2 team.

The DLR Institute of Space Systems in Bremen was responsible for developing and testing the lander together with CNES. The DLR Institute of Composite Structures and Adaptive Systems in Braunschweig was responsible for the stable structure of the lander. The DLR Robotics and Mechatronics Center in Oberpfaffenhofen developed the swing arm that allows MASCOT to hop on the asteroid. Das DLR Institute of Planetary Research in Berlin contributed the MASCAM camera and the MARA radiometer. The asteroid lander is monitored and operated from the MASCOT Control Center in the Microgravity User Support Center (MUSC) at the DLR site in Cologne.

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rrwillsj
not rated yet Oct 12, 2018
Another remarkable achievement of international cooperation and collective teams of scientists, engineers and technicians.
TeeSquared
not rated yet Oct 12, 2018
"But what was most surprising was that large accumulations of fine material are nowhere to be found – and we did not expect that. We have to investigate this in the next few weeks, because the cosmic weathering would actually have had to produce fine material," continues Jaumann"

Maybe because the asteroid is not that old?
Protoplasmix
5 / 5 (1) Oct 12, 2018
Made a 3-d stereo image of Hyabusa2's MASCOT deployment from images 1 and 3 here taken just after the lander's separation. Use the "crossed method" for viewing. For those unfamiliar or unable to view the image that way, just put your finger about 6 cm in front of your nose and focus your eyes on your finger with the image in the background. I used the free StereoPhoto Maker software to make the stereo image. Amazing how much more detail can be seen viewing Ryugu's surface that way...
danR
not rated yet Oct 13, 2018
"But what was most surprising was that large accumulations of fine material are nowhere to be found – and we did not expect that. We have to investigate this in the next few weeks, because the cosmic weathering would actually have had to produce fine material," continues Jaumann"

Maybe because the asteroid is not that old?
I would conjecture that under the constant flux of micrometeoritic dust, material is being blasted clean off the rock as rapidly as it is formed. The gravity being almost 5 orders of magnitude less than earth's, no ejecta is 'falling' back, and equally little exogenous material settles. What little does settle eventually (very eventually) gets knocked off by said not-so-settling meteorites.
tl;dr: the thing is constantly getting dusted off.
peabody3000
not rated yet Oct 13, 2018
i figure the missing dust is under the craggy surface. it ends up in channels leading underground like rainwater disappears into storm drains
TeeSquared
not rated yet Oct 13, 2018
I would conjecture that under the constant flux of micrometeoritic dust, material is being blasted clean off the rock as rapidly as it is formed. The gravity being almost 5 orders of magnitude less than earth's, no ejecta is 'falling' back, and equally little exogenous material settles. What little does settle eventually (very eventually) gets knocked off by said not-so-settling meteorites.


Now we have two very plausible choices.
rrwillsj
not rated yet Oct 13, 2018
My guesstimate is similar to danR's. Some of the asteroidal dust could be scoured away by a passing stream of extracurricular dust?

Plus additionally, I would suspect that every time a large rock would give the asteroid a good thump? That whatever dust was present would "jump".

Like an old fashion carpet-beater hitting a rug hung on a line.

The accumulated rocks found are adhering to the surface of Ryugu with mutual gravitational attraction.

When the dust particles are knocked loose, the attraction is much less etween the larger body and each tiny dust particle.

Which is when Solar Winds or other energetic phenomena can push the dust far enough away to avoid recapture.
Protoplasmix
not rated yet Oct 13, 2018
When the dust particles are knocked loose, the attraction is much less between the larger body and each tiny dust particle
Hm, this is kind of a trick question: if you were standing on Ryugu and dropped a bowling ball and a feather at the same time from the same height, which one would impact the surface of Ryugu first?
rrwillsj
5 / 5 (1) Oct 14, 2018
Pro, if you were asking me to do it? first the feather, carefully removing my hand from under it. I would assume, not much right away. The feather has a low mass for such a large surface area. I think the Solar Wind would waft it away before Ryugu's gravitational attraction couid capture it.

As for the bowling ball? The mutual attraction between the mass of the ball and the asteroid probably would, slowly, be sufficient to pull the bowling ball onto the surface.

Except... Well, I am a very clumsy man. Oh, yeah!

I have no doubt I would most likely, accidentally drop the ball to land om one of my feet. Yeah, that's pretty much a given.

Whereupon and forthwith I will reflexively kick it too far to re-orbit Ryugu.

If anything should intersect it's random flightpath? Do you think I could pick-up a spare?
HenryE
not rated yet Oct 16, 2018
This image was clearly heavily edited. When you magnify the image, you can tell that the "shadow" was placed there by photoshop or some other image editing technique.

There was certainly no spotlight shining down on the craft as it was flying and yet there is a halo of light around the shadow.

Magnify the image and you will see that the area immediately around the "shadow" was heavily edited.

What gives? Why the phony image?
rrwillsj
not rated yet Oct 16, 2018
Henry, you are asking me? Or any of the other readers of these articles on this site?

My first kneejerk reaction was to suspect you of exaggerating the possibility of fraud. And then ask. "What would the manipulation of the image gain for anybody involved?"

Bringing me to the conclusion that you are just trolling. Deliberately stirring up controversy for whatever nefarious profit you might gain.

Have you any professional training or experience in techniques of photography? Or used Photoshop professionally?
Perhaps you are knowledgeable prepping porn images?
Even experience faking images for EU/Aether cultists to post to youtube could be accepted as credentials

However, on reconsideration?
The evidence of your accusation is only circumstantial.

So. I put it to you, Henry.
Have you contacted the authors of the article, the research team involved, whoever processed the sus[ecr photo for publication?

And asked for an explanation? What was their response?
HenryE
not rated yet Oct 17, 2018
Sometimes images are manipulated to enhance certain features for clarity. For all I know, this is one of those cases. Usually though, that is clearly mentioned.

I had hoped someone knowledgeable would respond with a valid reason for the manipulation of the image. Perhaps to aid in seeing the craft's shadow which might have otherwise gotten lost against the dark asteroid or for extrapolation of the flight path. Many possibilties come to mind.

I come to this site hoping to exchange comments with thoughtful, intelligent people.

Such a shame that the only one to respond this time, is nothing but an insulting jackass who didn't even bother to look at the magnified image before mouthing off.

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