Submitted by marketrent t3_y9u9o9 in science
This is the actual paper referenced by the press release. It does look like several papers on Ryugu were simultaneously published yesterday.
>Ryugu's nucleosynthetic heritage from the outskirts of the Solar System
>
>https://www.science.org/doi/10.1126/sciadv.add8141
Thanks! (The press release didn’t include hyperlinks.)
>Abstract
>Little is known about the origin of the spectral diversity of asteroids and what it says about conditions in the protoplanetary disk. Here we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids. Growth and migration of the giant planets destabilized nearby planetesimals and ejected some inwards to be implanted into the Main Belt.
>In this framework, most carbonaceous chondrites may have originated from regions around the birthplaces of Jupiter and Saturn, while the distinct isotopic composition of CI chondrites and Ryugu may reflect their formation further away in the disk, owing their presence in the inner Solar System to excitation by Uranus and Neptune.
SOUNDS LIKE PLANET X TO ME!
I know very little about space outside of being a Reddit browser… But this is my theory from reading the headline alone. Am I doing it right?
Not an actual full size planet, no. "Ryugu is thought to have originated from a ~100 km-diameter parent body" that was warm enough to be soaking wet on the inside. Some of the rocks marinated in the hot groundwater. "After aqueous alteration, the parent body was catastrophically disrupted by an impact; part of the material re-accumulated to form a rubble pile asteroid, Ryugu."
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Technically there are several Planet X candidates out there. Including Pluto I know of 5 “dwarf planets”, although I believe I heard recently that they discovered a 6th a while back.
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I've always thought of Planet X as a larger planet out past the TNOs, not Pluto and other dwarf planets.
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The asteroid belt is a great protector of this little blue ball. We are lucky to have it!
> great protector
Is it settled science it does more good than harm?
Some fragments eventually find their way into the inner Solar System, leading to meteorite impacts with the inner planets.
Asteroid orbits in the belt continue to be appreciably perturbed whenever their period of revolution about the Sun forms an orbital resonance with Jupiter- with some swept into new orbits dangerous to earth.
Jupiter is considered the great protector because it removed 99% of the Asteroid Belt in the early days of the Solar System. Those early days produced heavy bombardment, as craters on the Moon and Mars demonstrate. But since then things have been "relatively" benign.
Nice, but the subject I was questioning was if 'the asteroid belt' is also a great protector.
Well it’s great belt for ass whooping
The asteroid belt has minimal mass (3% of our Moon). So it doesn't affect its own members much, or stop anything else from passing through.
Jupiter is 850,000 times more massive than the entire belt, so it strongly affects their orbits. For example, any asteroid that has a simple ratio to Jupiter's orbit gets pulled in the same direction every time it is closest. This pulls it out of that orbit, creating gaps in the belt. Conversely other asteroids are trapped in resonant orbits to Jupiter - the Trojans and Hildas.
So the main belt is not a protector of earth but a danger as the orbits of belt asteroids can be changed by Jupiter's massive gravity – and by occasional close encounters with Mars or other objects. These encounters can knock asteroids out of the main belt, and hurl them into space in all directions across the orbits of the other planets- like earth.
Exactly. Japan sent a probe to the asteroid Ryugu and brought back samples. The samples indicate its material formed in the outer Solar System. but now it's orbit crosses Earth's (that's why the picked it to visit).
More generally, there are 30,000 known asteroids whose orbits come closer than 1.3 times the Earth's distance to the Sun. That compares to over a million other asteroids. These "near Earth asteroids)" have an orbit half-life of 10 million years, which is very short compared to the age of the Solar System.
So these asteroids need to be constantly resupplied, otherwise there would be none left. The giant planets, which is mostly Jupiter since it is heavier than everything else combined, are the main cause of orbit changes.
The near Earth asteroids are the ones most likely to hit Earth, which is why NASA has a search program for them, and why they just tested changing an orbit by hitting it. What we have going for us is space is really empty. Earth only takes up one part in 500 million of our orbital region. So the chance of any given random rock hitting us is low. On the other hand, there are many rocks. Dust and sand-sized ones hit us every day. That's what meteors in the night sky are.
Earth's orbit is 500million times it's diameter?
No. Our orbit is 23,455 times the size of the Earth. But there is a second dimension, above and below our orbit.
This plot shows the size of asteroid orbits relative to ours on the horizontal scale, and the tilt in degrees relative to the Earth's orbit. You can see the tilts go up to 30-40 degrees.
Any tilt above zero means when they cross our orbit's distance, they can be crossing above or below where the Earth will pass. They can only hit us if they cross our distance exactly on our path, and the Earth also happens to be at that point in our orbit at the same time.
This ever-changing nature of the universe is astounding!
Ah ha Aliens..... No not really...
Or possibly since ancient “folk lore” is continuously proven right, perhaps there was a planet there back when Saturn was a luminous sun. Which is why the ‘dark arts’ celebrate Saturn the way they do. I don’t mean dark in a bad way, just not presented in the same classical easy to understand way other beliefs are.
marketrent OP t1_it7k5t8 wrote
Papers published 20 October 2022:
>First asteroid gas sample delivered by the Hayabusa2 mission: A treasure box from Ryugu
>https://www.science.org/doi/10.1126/sciadv.abo7239
>Abstract
>The Hayabusa2 spacecraft returned to Earth from the asteroid 162173 Ryugu on December 6, 2020. One day after the recovery, the gas species retained in the sample container were extracted and measured on-site, and stored in gas collection bottles. The container gas consists of helium and neon with an extraterrestrial 3He/4He and 20Ne/22Ne ratios, along with some contaminant terrestrial atmospheric gases. A mixture of solar and Earth’s atmospheric gas is the best explanation of the container gas composition. Fragmentation of Ryugu grains within the sample container is discussed based on the estimated amount of indigenous He and the size distribution of the recovered Ryugu grains. This is the first successful return of gas species from a near-Earth asteroid.
and
>Noble gases and nitrogen in samples of asteroid Ryugu record its volatile sources and recent surface evolution
>https://www.science.org/doi/10.1126/science.abo0431
>Abstract
>The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth’s volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measure noble gas and nitrogen isotopes in Ryugu samples, finding they are dominated by pre-solar and primordial components, incorporated during Solar System formation. Noble gas concentrations are higher than those in Ivuna-type carbonaceous (CI) chondrite meteorites. Several host phases of isotopically distinct nitrogen have heterogeneous abundances between the samples. Our measurements support a close relationship between Ryugu and CI chondrites. Noble gases produced by galactic cosmic rays, indicating ~5 Myr exposure, and from implanted solar wind, record the recent irradiation history of Ryugu after it migrated to its current orbit.