US, WASHINGTON (ORDO NEWS) — The spacecraft Hayabusa2, built and operated by the Japan Aerospace Exploration Agency or JAXA, launched a 5-gram metal shell on the surface of the near-Earth asteroid Ryugu, a body in the shape of a rotating rock, about 1 kilometer across and located about 350 million kilometers from Earth.
This shell destroyed the surface of the asteroid, allowing Hayabusa2 to capture some of the material that had taken off and safely collect it. It is expected that after departing from Ryugu in November 2019, Hayabusa2 will fly past Earth at the end of 2020 and dump the collected samples in a capsule to Earth, for detailed analysis in laboratories around the world.
In a new article published in the journal Science, the Hayabusa2 team reports on their observations of the sampling process itself and what measurements of the Ryugu surface as a whole can tell us about its evolution. These observations draw a wonderful story about a space traveler who traveled from the main asteroid belt, making a short excursion near the Sun, before ultimately settling in orbit in our area as a near-Earth asteroid.
I am a planetary scientist and I admire why planetary bodies look the way they look. Having understood how and why Ryugu acquired its present appearance, we will get a more complete model of the formation and development of bodies of the solar system, including ordinary carbon-type C-type asteroids, one of which is Ryugu.
A new article describes why some parts of Ryugu are bluer and others are redder.
These terms refer to subtle variations in the color of the surface of an asteroid in the visible spectrum. Hayabusa2 team found that the equator and the poles of the asteroid are bluer and the middle latitudes are redder. Interestingly, this color difference may be related to age, or rather, how long the material is exposed to the direct impact of space. This is due to the fact that open surfaces are darkened and redden due to weathering in space – bombardment by micrometeorites, solar and cosmic particles and heating by the Sun.
When Hayabusa2 fired its shell from a distance of about a meter, and then slowly walked away from the asteroid, a cloud of redder, darker pebbles and small grains burst out before falling back to the surface, turning the sampling area from slightly blue to slightly red.
This observation gave the team an idea of the latitudinal “bands” on Ryuga. Open material, reddened by the Sun and space weathering, slowly moves under weak gravity of the asteroid from the topographically high equator and poles to topographically low mid-latitudes. This movement carries the fresher, bluer material to the equator and poles and precipitates reddened material between them.
What struck me most was the fact that, from analyzing the size and color of the craters in Ryuga, the Hayabusa2 team came to the conclusion that at some point the asteroid should be closer to the Sun than it is now.
This explains the amount of redness on the surface. Using two different models to calculate the age of the craters, the team calculated that this redness caused by solar heating should have occurred either eight million years ago, or most recently, 300,000 years ago – just blinking an eye in space measures.
This information from the craters, based on images collected by Hayabusa2, also shows that the age of the surface of the asteroid itself is probably no more than 17 million years.
And so it turns out that a simple sampling on a rather unremarkable asteroid revealed the detailed life history of this asteroid, starting from its formation, through its journey through the internal solar system and ending with the processes that continue to form its surface today. The fact that we can learn a lot by visiting an asteroid and characterizing its surface is amazing. What else do we know when we get these samples?
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