Japan's Hayabusa probe arrives at asteroid Ryugu

Ryugu is a near Earth asteroid that occasionally crosses Earth's orbit (hence presents a small risk of colliding with Earth). But that means that it's close by and available for exploration. It's a little thing, only about 1 kilometer across at its widest point. It has distinct poles and an equatorial ridge, probably caused by its rotation and its very low gravity.

So the Japanese Space Agency (JAXA) launched their Hayabusa probe. It arrived in June and has been very slowly approaching since. Gravity's too low for Hayabusa to orbit, so it's basically flying in formation with Ryugu. It's about 1 km away now. In September, all kinds of things are scheduled to happen. Hayabusa will fire a large copper bullet at Ryugu (there must be a counter-thruster to keep from propelling itself away) in hopes of blowing away the surface material and creating a crater. There's a small separately deployable camera that will watch the impact from close-up. Then Hayabusa will release 4 mini-probes with cameras including a lander that will bounce more than crawl over Ryugu's surface. (Gravity is so low that wheels turning might propel a rover into outer space.) These should return high resolution photos. (One of these probes is from the European Space Agency.)

Finally Hayabusa is supposed to land in the crater it made and collect samples, which it will then return to Earth.  

[Image: 260px-162173_Ryugu.jpg]

According to Asterank, Ryugu is worth 82 billion dollars in chemical / mineral composition. I would have felt it would cost that much (maybe several times more) just to mine it and deliver the resources back to Earth. But there's an estimate of 30 billion dollars in profit.

(Aug 29, 2018 07:49 AM)C C Wrote: According to Asterank, Ryugu is worth 82 billion dollars in chemical / mineral composition.

Isn't that a bit premature? Hayabusa still hasn't determined what Ryugu is made of. These estimates seem to be assumptions based on the class of asteroid, jumping to the conclusion that it's made of valuable stuff like iron and cobalt.

It's hard to say from looking at it. It seems to be covered with a surface layer that's perhaps been attracted to it by its tiny gravitational field over the billions of years. I wonder what its consistency is. Is it like a fine fluffy dust or is it hard and baked-on? I believe that scientists are very interested in the surface material since it should provide some information about the chemistry happening out there in space, something of interest to astrobiologists and others. What kind of organic compounds are present?

As Hayabusa has been slowly approaching, its controllers have been mapping Ryugu's gravitational field, so they probably have good ideas about its overall mass and density. I guess that the bullet is intended to create a crater by blowing away the surface layer, in hopes of determining what's underneath.


Here's a photo from the Japanese Aerospace Exploration Agency (JAXA), taken by Hayabusa's Optical Navigation Camera - Telescopic, showing Ryugu from about 6 km away:

[Image: fig1.jpg]
The escape velocity of Ryugu is about 1 mph. So any of the large rocks seen in the picture must (surely?) have joined Ryugu at less than (say) 5 mph otherwise they would have blasted a crater and displaced far more mass than they added. The whole thing (almost everything) has come out of supernovae and yet we see a bunch of rocks and dust cruising along with hardly anything them together. I know nothing.
(Oct 1, 2018 03:12 AM)Yazata Wrote: The little bouncing rovers are down on the surface and are sending back photos.

The larger rover MASCOT yet to land sometime in October (originally scheduled for the 3rd). It will have a lifespan shorter than a mayfly.

Jonathan McDowell is reporting (on his twitter page) that Yahoo Japan is saying that JAXA (the Japanese space agency) is worried about all the large boulders MINERVA and MASCOT revealed on Ryugu, and won't attempt to do the Hayabusa-2 sample collection landing until at least January.


The story is in Japanese, but Google Translate's English version includes this:

"According to JAXA, from the photographs taken by the miniature exploration robot " Minerva 2 " that was dropped in September , it was found that rocks of 50 centimeters or more, which are obstacles to landing, are wide on the ground."
The Japanese Aerospace Exploration Agency (JAXA) is having their Hayabusa-2 spacecraft SHOOT at Asteroid Ryugu as we speak. (Space terrorism!)

They've released an explosive impactor, followed by little camera drone spacecraft, while the main Hayabusa backs away (and say's "Who Me? I didn't do anything.")

The idea is to create a crater, allowing them to determine what is immediately under the surface.

Watch it live here. They've even dubbed the Japanese commentary into English!


[Image: D3JeD1dUwAA_HjY.jpg]

Edit: Camera drone vehicle in position. Impactor should have just detonated but no confirmation yet. They just got confirmation that Hayabusa has backed off and is safely away from the explosive. They still haven't gotten any photographs, but they take a while to get to Earth, even at the speed of light. As I write this, they are trying to confirm that the little camera drone vehicle was pointed the right way.

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