The Hayabusa 2 probe had an eventful evening yesterday, some 186 million miles (300 million kilometers) from Earth. The Japan Aerospace Exploration Agency (JAXA) sent a long-awaited command, and the probe landed on the surface of the asteroid Ryugu, shot it with a bullet, and floated back upward. The goal was to collect material from the asteroid, but we don’t know how much asteroid regolith Hayabusa 2 scooped up.
JAXA had to plan the landing very carefully — Hayabusa 2 was too far away to control in real-time, so the probe had to run on autopilot. Surface analysis carried out with the MINERVA-II1A and MINERVA-II1B landers showed the surface of Ryugu to be much more uneven than the team had expected. Hayabusa 2 needed enough open space to extend its sampling horn to make contact with the surface.
According to JAXA, Hayabusa 2 made it to the surface as intended. As soon as it made contact, the probe fired off a 5-gram “bullet” composed of the high-density metal tantalum at more than 300 meters per second. The impact created a cloud of dust and rock fragments, some of which fell into the collection tube. JAXA confirms that Hayabusa 2 has retreated to a safe distance following the sample collection.
Hayabusa 2 still has another tantalum bullet in the chamber with Ryugu’s name on it. JAXA hasn’t offered specifics on when it will use that one, but a subsurface sampling is currently scheduled for April of this year. The surface of Ryugu has been exposed to solar radiation for billions of years, so material inside the asteroid may have a different composition. To get at it, Hayabusa 2 is going to have to blast a crater.
[TD1-L08E1] 2/22 at 8:42 JST. The following has been confirmed at Gate 5: ・Projectile was command to fire.・Normal sequence.・Spacecraft state is normal.Based on this, we determined touchdown was successful! A detailed analysis will now be done.
To do that, the probe will use the Small Carry-on Impactor (SCI). Hayabusa 2 will deploy this device and then retreat to a safe distance on the other side of the asteroid. The SCI carries an HMX shaped explosive charge that will accelerate a 5.5 pound (2.5 kilograms) copper impactor into the surface. Hayabusa 2 will wait about two weeks for the particulates to settle before descending into the newly formed crater to grab a sample.
JAXA hopes to get as much as 100 milligrams of material from Ryugu over the course of the mission. We won’t know for certain how much of Ryugu Hayabusa 2 collected until the sample return container gets back to Earth in late 2020.
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