A report on what the subtle colour differences of regions of Ryugu may tell us about its history

>…In a new paper published in Science, the Hayabusa2 team reports on their observations of the sampling process itself, and what measurements of Ryugu’s surface generally can tell us of its evolution. These observations paint a remarkable story of a cosmic traveler that traveled from the main asteroid belt, taking a short-lived excursion near the Sun, before ultimately settling into an orbit in our neighborhood as a near-Earth asteroid.

…The new paper describes how some parts of Ryugu are “bluer” and others are “redder.”

These terms relate to subtle variations in color of the asteroid surface across the visible spectrum. The Hayabusa2 team found that the equator and poles of the asteroid are bluer, whereas the midlatitudes are redder. Intriguingly, this color difference may be tied to age – or, rather, how long material is directly exposed to space. That’s because exposed surfaces are darkened and reddened by space weathering – bombardment by micrometeorites, solar and cosmic particles – and heating by the Sun, which is the primary mechanism for Ryugu.

…What I found most exciting was that, from the analysis of the size and colors of craters on Ryugu, the Hayabusa2 team concluded that at some point the asteroid must have been closer to the Sun that it is now. That would explain the amount of reddening of the surface. Using two different models for calculating the age of craters, the team estimated that this solar heating-induced reddening must have happened either eight million years ago or as recently as 300,000 years ago – a mere blink of an eye, cosmologically speaking.

(Full report at link above)

Bubblecar said:

A report on what the subtle colour differences of regions of Ryugu may tell us about its history

>…In a new paper published in Science, the Hayabusa2 team reports on their observations of the sampling process itself, and what measurements of Ryugu’s surface generally can tell us of its evolution. These observations paint a remarkable story of a cosmic traveler that traveled from the main asteroid belt, taking a short-lived excursion near the Sun, before ultimately settling into an orbit in our neighborhood as a near-Earth asteroid.

…The new paper describes how some parts of Ryugu are “bluer” and others are “redder.”

These terms relate to subtle variations in color of the asteroid surface across the visible spectrum. The Hayabusa2 team found that the equator and poles of the asteroid are bluer, whereas the midlatitudes are redder. Intriguingly, this color difference may be tied to age – or, rather, how long material is directly exposed to space. That’s because exposed surfaces are darkened and reddened by space weathering – bombardment by micrometeorites, solar and cosmic particles – and heating by the Sun, which is the primary mechanism for Ryugu.

…What I found most exciting was that, from the analysis of the size and colors of craters on Ryugu, the Hayabusa2 team concluded that at some point the asteroid must have been closer to the Sun that it is now. That would explain the amount of reddening of the surface. Using two different models for calculating the age of craters, the team estimated that this solar heating-induced reddening must have happened either eight million years ago or as recently as 300,000 years ago – a mere blink of an eye, cosmologically speaking.

(Full report at link above)

Noice

One thing I don’t get still about Ryugu (and the other sample-return target, Bennu): why are they so octahedral?

dv said:

One thing I don’t get still about Ryugu (and the other sample-return target, Bennu): why are they so octahedral?

https://quantumdynamics.wordpress.com/2018/07/02/octahedral-gravity-asteroid-162173-ryugu/

fsm said:

dv said:

One thing I don’t get still about Ryugu (and the other sample-return target, Bennu): why are they so octahedral?

https://quantumdynamics.wordpress.com/2018/07/02/octahedral-gravity-asteroid-162173-ryugu/

Earth’s gravity is also slightly weaker at the equator.

dv said:

One thing I don’t get still about Ryugu (and the other sample-return target, Bennu): why are they so octahedral?

So far as I know, nobody expected it. Because no previous moon or asteroid is that shape. And now we have two in a row.

The standard shape for a rotating body is oblate spheroid, unless it’s rotating too fast in which case it goes peanut-shaped. And let’s face it, everything rotates. Rotation explains the ridge around the equator but not the pointy poles.

For something rotating really fast, the peanut shape is the standard, and we’ve seen that with other asteroids and comets. Or a peanut shape can come from two spheres coming together in a gentle impact.

The pointy poles must just be accidental, for instance starting with something long and thin that happened by chance to be rotating along its long axis and then accreting material preferentially around its equator.

mollwollfumble said:

dv said:

One thing I don’t get still about Ryugu (and the other sample-return target, Bennu): why are they so octahedral?

So far as I know, nobody expected it. Because no previous moon or asteroid is that shape. And now we have two in a row.

The standard shape for a rotating body is oblate spheroid, unless it’s rotating too fast in which case it goes peanut-shaped. And let’s face it, everything rotates. Rotation explains the ridge around the equator but not the pointy poles.

For something rotating really fast, the peanut shape is the standard, and we’ve seen that with other asteroids and comets. Or a peanut shape can come from two spheres coming together in a gentle impact.

The pointy poles must just be accidental, for instance starting with something long and thin that happened by chance to be rotating along its long axis and then accreting material preferentially around its equator.

> These terms relate to subtle variations in color of the asteroid surface across the visible spectrum. The Hayabusa2 team found that the equator and poles of the asteroid are bluer, whereas the midlatitudes are redder. Intriguingly, this color difference may be tied to age – or, rather, how long material is directly exposed to space. That’s because exposed surfaces are darkened and reddened by space weathering – bombardment by micrometeorites, solar and cosmic particles – and heating by the Sun, which is the primary mechanism for Ryugu.

Well, that blows that hypothesis of mine out of the water. The poles are new, not old.

Hold on. The age thing could be related to size, small objects because of their larger surface area to volume ratio age faster. So the poles being larger could exhibit a bluer colour even though older. The blue being material exposed on the surface later.