Two Solar System puzzles solved

Jul 25, 2012
Solar system. Image: Wikipedia.

Comets and asteroids preserve the building blocks of our Solar System and should help explain its origin. But there are unsolved puzzles. For example, how did icy comets obtain particles that formed at high temperatures, and how did these refractory particles acquire rims with different compositions? Carnegie's theoretical astrophysicist Alan Boss and cosmochemist Conel Alexander are the first to model the trajectories of such particles in the unstable disk of gas and dust that formed the Solar System. They found that these refractory particles could have been processed in the hot inner disk, and then traveled out to the frigid outer regions to end up in icy comets. Their meandering trips back and forth could help explain the different compositions of their rims. The research is published in Earth and Planetary Science Letters.

The young Sun is thought to have experienced a series of outbursts caused by the rapid infall of disk gas onto the Sun. The leading mechanism for explaining such outbursts is a phase of disk instability. The researchers modeled the trajectories of several hundred centimeter-sized melilite mineral particles during a phase of disk instability. These particles are similar to calcium-aluminum-rich inclusions (or CAIs), the refractory particles often found in well-preserved meteorites, as well as the .

Their disk model assumed a marginally gravitationally unstable, fully three-dimensional disk, with a mass of about 5 % of today's Sun and temperatures ranging from a frigid -350 °F (60K) in the outer regions, to a scorching 2240 °F (1500K) near the center. Their calculations allowed the CAIs to orbit in the disk while being subjected to gas drag and the gravity of both the disk and the Sun.

The particles started orbiting in unison, but after about 20 years their started to diverge significantly. Most struck the inner boundary of the disk at 1 AU (the Earth/Sun distance), while others went to the outer boundary at 10 AU, where they could be swept up by a growing comet. About 10% migrated back and forth in the disk before hitting one or the other boundary.

The researchers then modeled the evaporation and condensation processes that the particles would experience during their migrations and found that such particles were likely to acquire outer rims with varied isotopic compositions recently shown to characterize CAIs.

"CAIs are thought to have formed at the very beginning of the . Our results show that they must have experienced remarkably complex histories as they were transported chaotically all over the disk," remarked Alexander.

These migrations could explain the different oxygen isotopes that have been found in particles from meteorites. These are varieties of oxygen atoms with different numbers of neutrons, which point to different processing conditions for the particle rims.

Previous work by Boss had shown that oxygen isotope abundances could vary in an unstable disk by the range found in meteorites. Coupled with the new results, these models show that several puzzles may have been solved—an unstable disk can explain both large-scale outward transport of refractory particles, as well as the peculiar rim compositions acquired during their journeys.

"It's nice to solve two problems at once," said Boss. "But there are still many more puzzles about meteorites for us to work on."

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User comments : 14

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2.7 / 5 (3) Jul 25, 2012
More silly "so called" quotation marks in the image! Someone forgot to label the "Sun".
1 / 5 (3) Jul 25, 2012
Carnegie's theoretical astrophysicist Alan Boss and cosmochemist Conel Alexander are the first to model the trajectories of such particles in the unstable disk of gas and dust that formed the Solar System.

How do you deal with the fact that other researchers have shown that the disk model does not work, for reasons not mentioned in this article? Heck, they even published their findings and there was an article on this very site a few months back, and I had theorized the same findings a few years earlier on this very site and physforums site.

Only a spherical model can explain Uranus and it's moons condition with such a highly tilted axis for the planet, as well as orbital plane for the moons, and even that is a long stretch.

10a.u. is directly in Saturn's orbit, and would be gobbled up by that giant planet, so does not explain the formation of surviving comets at all. In fact it refutes the model.
1 / 5 (2) Jul 25, 2012
Do we need a reminder but, yeah true, though its "Sol", latin if I remember correctly as name for our particular Sun.

Models tend to be asymptotic and consideration of chaotic influences do need to be factored in, we can never have direct knowledge unless we have time travel, so lets not whine please...
1 / 5 (5) Jul 25, 2012
More characteristic imprecision. The title of the article declares the mysteries "solved", but the article itself only offers a suggestion of what "could" have occured.
And there have always been suggestions for claimed manifestations in comets and meteoroids. High temperatures were described as caused by collisions of asteroids. Accrestion under differing circumstances could produce particles with rims of different materials. These processes can occur even far out in an accreting disk and so didn't need the extra mechanism of having them tossed outward.
So often, "favored sons" in the "science" community are allowed to introduce new "theories", even if inferior to older models. Careful popularization in the "media", and the fact that even many "science" devotees don't know what happened the day before yesterday, facilitates inferior models displacing older better ones that no one stands to make a profit on promoting.
5 / 5 (1) Jul 25, 2012
Nothing new with these "thoughts" and nothing solved yet. Just a simulation that works.
Ok, step by step.
Who is responsible for those sensacionalist titles?
not rated yet Jul 26, 2012
This is akin to the X-wind models that shows disk mixing as the protostar gets its magnetic field and the constrained jet outflows of T Tauri young stars. There the dust rains back onto the disk while gas is dispersed through the jets.

But now mixing is extended to the while disk lifetime. This tests observations of mixed grains in comets, and now specifically early CA inclusions (CAI). The interrupted disk is precisely what is observed when people include the ionization effects properly. Turns out that the magnetic-rotational instability then turns on and off, thoroughly mixing material in brief spurts. [ http://astrobites...ater-go/ ]

This is how astrophysicists were able to predict Earth-Moon and Mars similar initial low water content independent of the new observations establishing it. So this is all very predictive, it is exciting to know so much about the early system!
not rated yet Jul 26, 2012
Creationists should comment on science, it is hilarious!

The disk model is the accepted model of early protoplanetary systems, and it is plenty observationally verified. How ignorant must you be to implicitly claim that it isn't mainstream?

Or to discuss the early system with its migrating planets as how it looks today? In the modern Nice theory with Grand Tack, Jupiter and Saturn where tacking down towards 2 au before Jupiter was turned around and the resonance scattered the system. NT w ejected 5th giant predicts 20ish observations on the system (size, asteroid belt and its parameters, size and orbits of J/S/U/N, diverse trojans and their parameters, Kuipers and their parameters, et cetera).
not rated yet Jul 26, 2012
@ julianpenrod:

It is a testable hypothesis extending on what is known, and it tests well. No favoritism, it is peer reviewed published.

And conspiracy theories? Please, they are always the least likely explanation by construction (people don't want them testable, hence they are unlikely).

@ Anda:

It is a hypothesis that solves a problem, it isn't an ad hoc untestable model. If you don't understand testing of observations and hypotheses/theories against agreed on degrees of uncertainty, you will have a terrible time understand modern science or rather, I think you can't. Look at the creationists for example, they blather over inductionism that was a theological description of "acceptable" science 200 years ago. Science is _twice_ that age, and we have made exp progress.

No more or no less is promised in the title. Remember, one correct hypothesis is enough, and when they claim solved there were no suitable hypothesis before. CAI mixing wasn't covered in the X-wind model AFAIK.
5 / 5 (2) Jul 26, 2012
[cont after editor crapped out]

Look at the creationists for example, they blather over 'inductionism' that was a theological description of "acceptable" science 200 years ago. Science is _twice_ that age, and we have made exponential progress into "unacceptable" science.

For example finding out that universes arise naturally from physicals laws while 'creators' are unnecessary and very unlikely and that physical laws comes out of selection naturally such as anthropic selection while again 'creators' are unnecessary and very unlikely.

The problem for creationists are that they think 'inductionism' is valid because that is how theology works in exegesis, disputation and apologetics, you cherry pick and use sophistry to verify your confirmation bias. See how they comment by Gish gallop instead of analysis.
5 / 5 (2) Jul 26, 2012
You can't explain that without understanding that testing makes it possible to reject erroneous theory (testable) and ideas (untestable, like ad hoc models without explicit testability) such as on creators, both on the account that they simply doesn't work.
1 / 5 (1) Jul 26, 2012
@Torbjorn Larsson

Torbjorn don't you think if 'inductionism' was "acceptable" science 200 years ago then what's "acceptable" as science now'll be equally redundant in another 200 years (if not a lot sooner).

My point being has it never occurred to you the BELIEFS universes arise naturally from what we presently take to be physical laws and that these 'laws' come about from 'natural selection' might be superseded by 'explanations' presently inconceivable to us?

Look at natural selection itself - it's based on the idea what we presently know explains what happened in the past.

But circa the time of Darwin the natural selection explanation for bees being drawn to red flowers was because they'd evolved an attraction to red but we now know bees not only aren't attracted to red but most can't see it.

So we've now decided it's ultraviolet they're attracted to but it may turn out with some as yet undiscovered piece of information they're not attracted to ultraviolet either.
not rated yet Jul 26, 2012
@ alanborky:

No, and it is precisely why one must understand that testing rejects erroneous theories.

By some not well understood mechanism, perhaps because a finite observable universe only allows us finite resources for testing, the process has observably converged in one important case. everyday physics.

"The Laws Underlying The Physics of Everyday Life Are Completely Understood
Not sure why people dont make a bigger deal out of this fact."
not rated yet Jul 26, 2012

"A hundred years ago it would have been easy to ask a basic question to which physics couldnt provide a satisfying answer. What keeps this table from collapsing? Why are there different elements? What kind of signal travels from the brain to your muscles? But now we understand all that stuff. (Again, not the detailed way in which everything plays out, but the underlying principles.) Fifty years ago we more or less had it figured out, depending on how picky you want to be about the nuclear forces. But theres no question that the human goal of figuring out the basic rules by which the easily observable world works was one that was achieved once and for all in the twentieth century.

You might question the once and for all part of that formulation, but its solid. Of course revolutions can always happen, but theres every reason to believe that our current understanding is complete within the everyday realm."

- Theoretical physicist Sean Carroll -
not rated yet Jul 26, 2012

[ http://blogs.disc...erstood/ ]

Specifically evolution, which in the way of biologists have been a frame for new theory like neo-darwinism instead of being a specific theory, is our best tested theory and fact of all of science, because it is so complex. In fact it contains _the best observed fact we have and ever will have_ because of combinatorial growth of phylogenies, the existence of a DNA LUCA: it is ~ 10^2000 more likely than separate common ancestors.

The likelihood for replacing all that with a better, more predictive theory is truly astronomical, on the order of separate common ancestors.