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Hayabusa 2 Finds Asteroid Ryugu Is Young, Dark & Dry – Sky & Telescope

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Hayabusa 2’s asteroid Ryugu has some surprising traits. Particularly, its dry floor may spell bother for present theories about how Earth obtained its water.

Ryugu close-up

Hayabusa 2’s Optical Navigation Digital camera captured this picture of Ryugu on June 26, 2018.
JAXA / College of Tokyo and collaborators

It’s the week of the asteroids! In the course of the Lunar and Planetary Science Convention held in Texas, the 2 mission groups — NASA’s Osiris-REX and the Japanese Aerospace Exploration Company’s Hayabusa 2 —up to date the neighborhood on their explorations of near-Earth asteroids. The displays have been accompanied by photos and knowledge, in addition to a slew of papers within the journals Nature, Nature Astronomy, and Nature Geoscience.

We’ve already reviewed NASA’s Osiris-REX findings on the asteroid 101955 Bennu. Now let’s check out updates from the workforce behind Hayabusa 2, in orbit round 162173 Ryugu. The Japanese workforce is a bit forward of their American counterparts, having arrived roughly six months earlier. Upon method, the workforce discovered the identical form of unexpectedly tough terrain that NASA finally discovered at Bennu: Ryugu is peppered by boulders and rocks a number of meters in diameter, which threaten the spacecraft because it retrieves samples from the floor.

Whereas the Osiris-REX workforce remains to be planning the spacecraft’s descent to Bennu, Hayabusa 2 has already efficiently deployed three landers that floated to the asteroid’s floor, snapping photos alongside the way in which. The mothership has additionally already accomplished one of many three anticipated landing maneuvers.

Throughout these touchdowns, the spacecraft extends a pattern retrieval mechanism, which seems like a 1-meter-long limb that ends in a canister for gathering samples. When the canister is shut sufficient to the floor, a particular mechanism throughout the limb shoots a pinball-sized bullet to the asteroid’s floor, stirring the regolith within the hopes that a few of the floor materials will find yourself contained in the canister. Earlier this month, the workforce launched footage of the primary try. The researchers count on to have extra materials than they initially deliberate to gather, for the reason that bullet created a extra energetic response than they’d predicted — it jostled close by rocks as much as 1 meter in diameter.

Nonetheless, there isn’t any method to know for positive how a lot they obtained, for the reason that spacecraft has no mechanism to weigh or estimate what’s contained in the pattern chamber. “That is to maintain issues attention-grabbing till the Earth return,” joked mission program supervisor Yuichi-Tsuda (JAXA’s Institute of Area and Astronautical Science) throughout the press convention. “It’s like a memento current field.”

Ryugu: Like and Not Like Bennu

Ryugu and Bennu are so related in look, it’s laborious to inform them aside in photos. Each have been known as “rubble-pile asteroids,” collections of quite a lot of different-sized particles held collectively by gravity. Their low densities indicate their interiors are filled with hole areas, like Swiss cheese. These objects most likely got here collectively out of the items left over from bigger asteroids, which can have come aside throughout impacts within the early photo voltaic system.

Each objects are formed like spinning tops, as their fast rotation causes a ridge to kind alongside the equator. However whereas Bennu’s rotation is accelerating, Ryugu seems to have slowed down, and it’s unclear why. It’s present rotation interval is 7.6 hours, however researchers estimate that sooner or later in its previous, it will need to have rotated extra rapidly, with a interval shorter than three.5 hours, so as to purchase its present form.


Ryugu is about 900 meters (or about half a mile) vast.
© 2019 Seiji Sugita et al., Science

There may be additionally a giant distinction in age. Whereas Bennu is historical, with an estimated age starting from 100 million to 1 billion years, Ryugu seems to be a lot youthful, lower than 100 million years outdated.

Ryugu can also be darker than Bennu, reflecting on common half the sunshine that that Bennu does. With a reflectivity, or albedo, of two%, it’s one of many darkest objects recognized within the photo voltaic system. Researchers have matched Ryugu’s noticed floor shade to 2 asteroid households in the primary asteroid belt, known as Polana and Eulalia. The similarity factors to certainly one of these teams as Ryugu’s almost definitely household of origin.

One other surprising distinction is within the quantity of water that researchers have discovered on the 2 asteroids. Whereas there are hydrated minerals on each objects, Ryugu seems to be a lot dryer than researchers anticipated, which means that its dad or mum physique didn’t have a lot water both. That is in distinction with Bennu, which has extra plentiful hydroxyls. These molecules include hydrogen and oxygen atoms bonded collectively and are most likely related to clay minerals, hinting at previous interactions with water.

Unraveling why the 2 asteroids have completely different water content material will likely be vital for understanding how Earth obtained its water. Photo voltaic system formation fashions typically assume that many of the water discovered on Earth in the present day arrived onboard meteorites and comets each from the asteroid belt and from the outer rims of the photo voltaic system. The existence of dry asteroids in Earth’s neighborhood may imply that these fashions have to be adjusted.

Ryugu, in false color

A false-color picture of Ryugu exhibits that its surprisingly missing water.
© 2019 Seiji Sugita et al., Science

Subsequent Steps: Fireplace the Cannon!

The following step for the Hayabusa 2 mission doesn’t sound very high-tech nevertheless it’ll be spectacular. On April fifth the spacecraft will hearth a 2.5-kilogram (5.5-pound) projectile at Ryugu With a purpose to create a synthetic crater on its floor. The workforce has already designated what level on the floor they wish to blast and goals to make a gap a minimum of 10 meters vast and 1 meter deep.

With this maneuver, the workforce expects to be taught extra about how asteroids react to impacts, which is able to assist scientists higher perceive Ryugu’s historical past and evolution. Details about the impression may also turn out to be useful in case certainly one of these items ever comes too near Earth, and we’ve to blast it out of the way in which.

Creating the crater may even allow researchers to peek at what lies under the floor. Two weeks after taking pictures the cannon, Hayabusa 2 will try a second sampling maneuver, aiming for the underside of the crater. Then, in November or December this 12 months, the spacecraft will begin its one-year return journey to Earth.

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