Results from tiny MASCOT lander on Ryugu

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The scientists in charge of the tiny MASCOT lander dropped from Japan’s Hayabusa-2 spacecraft today released the results from the lander’s short seventeen hour observations of the surface of Ryugu.

They found that the asteroid has two different types of rocks (why is a mystery) and practically no dust.

Ralf Jaumann and his team were particularly surprised by the lack of dust: “Ryugu’s entire surface is littered with boulders, but we have not discovered dust anywhere. It should be present, due to the bombardment of the asteroid by micrometeorites over billions of years, and their weathering effect. However, as the asteroid has very low gravity – only one-sixtieth of that experienced on Earth’s surface – the dust has either disappeared into cavities on the asteroid or has escaped into space. This gives an indication of the complex geophysical processes occurring on the surface of this small asteroid.”

They also confirmed that the asteroid is a very fragile rubble pile.

“If Ryugu or another similar asteroid were ever to come dangerously close to Earth and an attempt had to be made to divert it, this would need to be done with great care. In the event that it was impacted with great force, the entire asteroid, weighing approximately half-a-billion tonnes, would break up into numerous fragments. Then, many individual parts weighing several tonnes would impact Earth,” says Jaumann, who is supervising the MASCam experiment, interpreting the observations. The asteroid is very similar to carbonaceous meteorites found on Earth, which date back 4.5 billion years. With an average density of just 1.2 grams per cubic centimetre, Ryugu is only a little ‘heavier’ than water ice. But as the asteroid is made up of numerous pieces of rock of different sizes, this means that much of its volume must be traversed by cavities, which probably makes this diamond-shaped body extremely fragile.

MASCOT was another example of a cubesat demonstrating that these tiny spacecraft can do very sophisticated science.



  • Chris

    Just as the large stones in a vibrated pale “rise” to the top and the dust and the small ones fall; wouldn’t we expect the same on a loosely packed set of rocks held together by only gravity? I think the dust is at the center.

  • mpthompson

    It’s only inevitable that at some point humans will need to divert such asteroids. Either with urgency to remove a collision threat or for more benign commercial reasons. It would seem only prudent to be funding a lot more Hayabusa-2 and MASCOT type spacecraft to better research and understand what must be very complex dynamics of loosely held piles of rubble in space. Basic research and exploration today that would have very beneficial long term benefits.

    Also, Ryugu is very small and describing having “very low gravity” is almost an understatement. The acceleration due to gravity on the surface of Ryugu is estimated to be about 0.00011 m/s^2 verses about 9.8 m/s^2 on Earth. That is about 1/100,000 the gravity on Earth, not 1/60. The size and mass of Ryugu would have to be near that of Ceres to have 1/60 the gravity of Earth. DLR was a little sloppy with that statement.

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