Friday, February 22nd 2019, 6:00 pm - Japan blasts a sample from an ancient asteroid and Neptune's newest moon has a strange origin story. It's what's up in space!
HAYABUSA 2 BLASTS 1ST SAMPLE
Late Thursday night, or early Friday morning for the mission scientists, Japan's Hayabusa 2 spacecraft descended all the way to the surface of asteroid Ryugu, tapping down and blasting away a small bit of the space rock, before retreating.
This artist's conception drawing shows the Hayabusa 2 spacecraft coming in to touch down on the surface of asteroid Ryugu. Credit: JAXA
This is a major milestone for the Hayabusa 2 mission, which set off from Earth in late 2014, for a six-year round-trip flight to map and gather samples from 162173 Ryugu, a 1-km wide, roughly diamond-shaped asteroid that periodically crosses Earth's orbit.
Arriving at Ryugu in June of 2018, Hayabusa dropped three rovers onto the asteroid's surface, to help it search for a good place to collect samples from.
Based on the data they received back, the mission team chose their first sample location, and on Friday morning (local time for Japan), they anxiously watched the data feed from the spacecraft, as it drew closer to the asteroid, fired a metal bullet into the surface to blast away material for collection, and then retreated back into orbit.
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.
[TD1-L08E1] 2/22 at 8:42 JST. The following has been confirmed at Gate 5:— HAYABUSA2@JAXA (@haya2e_jaxa) HAYABUSA2@JAXA on Twitter: "[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. / Twitter"
・Projectile was command to fire.
・Spacecraft state is normal.
Based on this, we determined touchdown was successful! A detailed analysis will now be done.
This image, snapped by Hayabusa 2's cameras, shows the surface of asteroid Ryugu, with the spacecraft's shadow visible upper-left of centre, and the sample collection point, bottom-centre, which is shaded darker than its surroundings due to the freshly disturbed material. Credit: JAXA
There are two more sample collections planned before the spacecraft leaves the asteroid in 2020. Hayabusa 2 will drop these samples in a sealed capsule, when it arrives back home, so that scientists here on Earth can examine the materials in detail.
NEPTUNE'S STRANGE NEW MOON
Back in 2013, astronomers using the Hubble Space Telescope discovered that Neptune had a moon they hadn't previously noticed, which they eventually named Hippocamp.
As they observed it, they found that this tiny member of the Neptune family was a strange one, with an orbit that just wasn't right.
According to NASA, they called it "the moon that shouldn't be there."
Why? Because its orbit was far too close to its much larger neighbor, Proteus.
This orbital diagram of Neptune's closest 7 moons shows the position of the newest member of the Neptune system. Although it was discovered in 2013, the astronomers who found it managed to locate it in Hubble observations of Neptune, going back to 2004, thus the "2004" in its name. The moon's official name is now 'Hippocamp'. Credit: NASA, ESA, and A. Feild (STScI)
Now, after discovering that Neptune's largest moon, Triton, was very likely captured from the Kuiper belt, the idea was put forward that all of Neptune's other moons are very likely 'second generation'.
That is, Triton's capture disrupted and destroyed Neptune's first crop of moons, and once Triton settled into its orbit, the current, second-generation moons formed from the ring of debris.
The problem is, Hippocamp is so close to Proteus that, had it formed in its location, the same as the others, it would have been ejected from the Neptunian system by Proteus' gravity, or the larger moon would have dragged it in for an impact that would have absorbed it.
Yet, here Hippocamp is, circling the planet... so, where did it come from?
One clue came from Voyager 2 images of Proteus, which showed that the moon had likely been struck by a comet, sometime billions of years ago.
"In 1989, we thought the crater was the end of the story," Mark Showalter from the SETI Institute, who is the lead author of the study, told NASA. "With Hubble, now we know that a little piece of Proteus got left behind and we see it today as Hippocamp."
So, as it turns out, there likely was an impact in Hippocamp's history - specifically a comet impact with Proteus that broke off the 34-km wide mass, and left it behind as Proteus migrated farther away from Neptune.