How comets were assembled

May 29, 2015, University of Bern
Collision of two icy spheres with a diameter of about one kilometer. After a first impact the bodies separate and reimpact a day later.

Rosetta's target "Chury" and other comets observed by space missions show common evidence of layered structures and bi-lobed shapes. With 3D computer simulations Martin Jutzi of PlanetS at the University of Bern was able to reconstruct the formation of these features as a result of gentle collisions and mergers. The study has now been published online in the journal Science Express.

In a video sequence based on a computer simulation two icy spheres with a diameter of about one kilometer are moving towards each other. They collide at bicycle speed, start mutually rotating and separate again after the smaller body has left traces of material on the larger one. The time sequence shows that the smaller object is slowed down by mutual gravity. After about 14 hours it returns back to reimpact a day after the first collision. The two bodies finally merge to form one body that somehow looks familiar: The bi-lobed frame resembles the shape of comet 67P/Churyumov-Gerasimenko imaged by ESA's Rosetta mission.

The simulation is part of a study published in Science Express by Bernese astrophysicist Martin Jutzi and his US colleague Erik Asphaug (Arizona State University). With their three-dimensional computer models the researchers reconstruct what happened in the early solar system. "Comets or their precursors formed in the outer planets region, possibly millions of years before ," explains Martin Jutzi. "Reconstructing the formation process of comets can provide crucial information about the initial phase of planet formation, for instance, the initial sizes of the building blocks of planets, the so-called planetesimals or cometesimals in the outer solar system." About 100 simulations were performed, each one taking one to several weeks to complete, depending on the collision type. The work was supported from the Swiss National Science Foundation through the Ambizione program and in part carried out within the frame of the Swiss National Centre for Competence in Research "PlanetS".

67P/Churyumov-Gerasimenko isn't the only comet showing a bi-lobed shape and evidence for a layered structure. Crashing on 9P/Tempel 1 in 2005, NASA's Deep Impact showed similar layers, a feature that is also presumed on two other comets visited by NASA missions. Half of the comet nuclei that spacecraft have observed so far have bi-loped shapes among them comets 103P/Hartley 2 and 19P/Borelly. "How and when these features formed is much debated, with distinct implications for formation, dynamics, and geology," says Martin Jutzi.

Primordial remnants of a quiet phase

In their study the researchers applied 3D collisional models, constrained by these shape and topographic data, to understand the basic accretion mechanism and its implications for internal structure. As their three-dimensional computer simulations indicate, the major structural features observed on cometary nuclei can be explained by the pairwise low velocity accretion of weak cometesimals. The model is also compatible with the observed low bulk densities of comets as the collisions result in only minor compaction.

"These slow mergers might represent the quiet, early phase of planet formation, before large bodies excited the system to disruptive velocities, supporting the idea that cometary nuclei are primordial remnants of early agglomeration of small bodies," says Martin Jutzi. Alternatively, the same processes of coagulation might have occurred among debris clumps ejected from much larger parent bodies. Along with future using radar to directly image internal structure, the 3D are an important step to clarify the question of how the cometary nuclei were assembled.

Explore further: New images of comet 67P/Churyumov-Gerasimenko reveal an irregular shape

More information: "The shape and structure of cometary nuclei as a result of low-velocity accretion" Science DOI: 10.1126/science.aaa4747

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SnowballSolarSystem _SSS_
1 / 5 (7) May 29, 2015
Comet formation by gravitatonal instability, not by computer modeling:

I suggest the high percentage of contact-binary objects is telegraphing planetesimal formation by gravitational instability with binary fragmentation due to excess angular momentum. Subsequent perturbation of binary systems causes spiral-in mergers, resulting in contact binaries.

If chondrules are the limit of core accretion in the inner solar system, you still don't get to kilometer-scale comets in the outer solar system.
cantdrive85
1.6 / 5 (7) May 29, 2015
The bi-lobed shape is common in electric discharge phenomena, repeatedly recreated in the lab.

http://ieeexplore...=4287076
rossim22
1.4 / 5 (9) May 29, 2015
Contact binary is ridiculous, not to mention there is no ice observed on 67P. I don't care if you see water and hydroxyl, there are other methods of recreating those observations. Same with its apparent low density, it's indirectly derived from the attraction force of 67P on Rosetta. This requires that gravity (which is not even constant on earth) works exactly the same with this comet... it's an acceptable assumption but an assumption nonetheless.

So when you remove the researcher's bias and all indirectly obtained information, 67P is a hard rock with zero ice.
Stevepidge
1 / 5 (5) May 29, 2015
Did they simulate this with playdoh?
jonesdave
4.3 / 5 (11) May 29, 2015
@rossim22
That is the biggest pile of garbage I've read all day, and that's saying something! Gravity is not variable to any degree that makes any difference when planning space missions. Perhaps you'd care to tell us how something that should have a density of ~ 3000 kg m^3 has been measured at 470 kg m^3? Preferably with some maths involved. And no, it isn't due to electrostatic repulsion; we have a known voltage for the spacecraft of -5 - -10 V. It isn't difficult (for the scientifically literate) to estimate a capacitance for both the spacecraft and the comet. Plug those figures in, and you'll see that you need a charge on the comet of > 10 0000 Coulombs, and a voltage greater than 1 gigavolt to explain away that much of a discrepancy. And that would soon discharge.
While you're at it, you also might like to explain where all the water is coming from. And don't invoke the solar wind; it is at least 7 orders of magnitude too low to create 1 litre of water back in November-ish.
Captain Stumpy
5 / 5 (7) May 30, 2015
in the lab
@cd
except the above study is not based upon looking at pictures and thinking they are similar
There are two structural clues to cometary origin. First, there is a clear record of layers ( 18 , 19 ) in 9P/Tempel 1 and 67P/C-G, and possibly 19P/Borrelly and 81P/Wild 2. The layers of 67P range from structural (~10-100 m scale) to textural (meter-scale), and 9P/Tempel 1 has identifiable layers from >100 m to the limits of resolution (~10 m). Second, about half of comet nuclei have bi-lobed shapes (1P/Halley, 19P/Borrelly, 67P, 103P/Hartley 2). We apply 3D collisional models, constrained by these shape and topographic data, to understand the basic accretion mechanism and its implications for internal structure.
actual observed and measured data trumps lab experiments and hearsay/eyewitness conjectures

according to the study, there was no measured plasma discharge either

so the eu con is back
and cd leads the pseudoscience troll crowd
Captain Stumpy
4.8 / 5 (6) May 30, 2015
That is the biggest pile of garbage I've read all day, and that's saying something!
@jonesdave
keep up the good work

if you can, link some references and studies next time
especially studies

pseudoscience acolytes hate studies with legit science

PEACE

I won't waste money purchasing the article, "Plasma-Generated Craters and Spherules", with abstract
@FSC
he has tried to link that paper before from the thunderbutts site, but i wouldn't try to load it if i were you
(phishing/data compromise and spam/virus hazard)

if he gives an AAAS link, just ask me to send it to you via e-mail
you can contact me at Sciforums for my e-mail address
cantdrive85
1.6 / 5 (7) May 30, 2015
EU catechism requires its' unschooled and naive followers to believe that such results can safely be extrapolated many orders of magnitude in size, from millimeter and sub-millimeter spherules, up to objects in the kilometer size range.


Plasma processes have been "safely" shown to be scalable over 27 orders of magnitude, and speculatively to 40 orders. But if you ignorantly wish to believe the computer games of fanciful mathematicians over real laboratory evidence that puts you firmly in the camp of the theoretical dogmatists. When your only argument is "nuh uh!", it shows that you are clearly the joke. It also flies in the face of the fact that plasma processes far in excess of the necessary energies occurs on a daily basis in our solar system.
http://www.nasa.g...ale.html
Captain Stumpy
5 / 5 (6) May 30, 2015
When your only argument is "nuh uh!", it shows that you are clearly the joke. It also flies in the face of the fact that plasma processes far in excess of the necessary energies occurs on a daily basis in our solar system
@cd
so, as i pointed out in the study paragraph above: the actual measured data, which was observed and modeled, is the point of the study, not some lab experiment with speculative plasma discharge that (as the study also points out) was never measured

let me reiterate that for you: according to the study, there was no measured plasma discharge (esp not with Shoemaker-Levy)

actual observed and measured data trumps lab experiments and hearsay/eyewitness conjectures, especially from pseudoscience religions like eu

so, it means that, since your basic argument is "nuh uh! look at my religion(eu)", per your own words:
the joke is you
and definitely ON you as well
Captain Stumpy
5 / 5 (5) May 30, 2015
plasma processes far in excess of the necessary energies occurs on a daily basis in our solar system.
http://www.nasa.g...ale.html
@cd
also please note that these plasma discharges are:
1- on the sun
2- measurable with our instruments (this is important)

considering number two above:
IF we can measure plasma discharges
&
IF the bulk of the world was watching Shoemaker-Levy 9 collide with Jupiter
THEN
per your own arguments where you state SL9 was broken apart by plasma discharge, not gravity, then the plasma discharge should have been easily observed by our various world observers, or at least by a few that can/could validate the dinfings

now
given that this did NOT happen, then your eu conjecture has the same standing as ASSuming that santa clause bred with the tooth fairy which gave us the easter bunny

IOW - none

conjecture without evidence and validated science is simply personal opinion
NOT science
cantdrive85
1.6 / 5 (7) May 30, 2015
The trouble is, your EU is a single-shack ghost town


GR and QM have been shown to be either completely wrong (GR), or wanting for a great deal of correction (QM). They have been cast aside in favor of classical explanations that comply with observation and experimentation. Nuclear physics are understood as well as they are due to electrical engineers, it's the theoreticians who have led to failure after failure in re to fusion and fanciful beliefs. And there is plenty of maths regarding EE.

Regular readers here will know how utterly pointless it would be to ask you for references


http://articles.a...ype=.pdf

Of course, you choose to remain willfully ignorant. A simple search would reveal your own incompetence to research well understood knowledge. BTW, Peratt was chosen by the DOE to help maintain our nuclear arsenal.
Vietvet
5 / 5 (7) May 30, 2015


Of course, you choose to remain willfully ignorant. A simple search would reveal your own incompetence to research well understood knowledge. BTW, Peratt was chosen by the DOE to help maintain our nuclear arsenal.


So what, Tesla claimed he was receiving signals from Mars

http://www.tfcboo...2-09.htm
cantdrive85
1.7 / 5 (6) May 30, 2015
"So what" says a dolt, you miss your dementia meds Mr. Stalker Vietkiller? Did you read the passage? Are you suggesting we don't receive radio signals from space? Once again, Tesla had discovered empirically that which the mainstream of science claimed was not possible, then credit given to someone else entirely for discoveries of Tesla. Nowhere did he claim to know the source other than stating it wasn't likely the Sun or produced locally, although he speculated it could be of "intelligence control". But there is no doubt that we are able to communicate with Mars or the edge of the solar system for that matter.

BTW, was there a point to this comment? Or did you just want to look stupid as a rock? Are you suggesting the DOE is as shortsighted/ignorant as you?
Vietvet
5 / 5 (7) May 30, 2015


BTW, was there a point to this comment? Or did you just want to look stupid as a rock? Are you suggesting the DOE is as shortsighted/ignorant as you?


@cantdrive

My point is that an individual can make major contributions (Tesla and others), minor contributions (Kohl) and still go way off track.
cantdrive85
1.8 / 5 (5) May 30, 2015
Well you failed miserably, because nowhere above did Tesla go "off track". Was he speculating about life elsewhere? Sure, but scientists still do the same today. Hell, some scientists believe comets delivered life to Earth. The main messages in the article referred to wireless communications and background radio noise, both of which are very real phenomena. Whether you just scanned it or not, you clearly missed the point of the essay.
Captain Stumpy
4 / 5 (6) May 31, 2015
GR and QM have been shown to be either completely wrong (GR), or wanting for a great deal of correction (QM). They have been cast aside in favor of classical explanations that comply with observation and experimentation
@cd
by all means, show all these legitimate reputable scientists that are casting aside GR/SR
links/proof?
Nuclear physics are understood as well as they are due to electrical engineers, it's the theoreticians who have led to failure after failure in re to fusion and fanciful beliefs
that's why your eu and the ee's there have built so many fusion reactors that are powering the nation, right?

your claims are like every other claim you've made re: eu
unsubstantiated conjecture based upon conspiracy and delusional beliefs
not science

just because you believe in something doesn't make it true
eu is PSEUDOSCIENCE
that is why you've not built nuclear reactors or been able to get noticed by actual scientists
Stevepidge
1 / 5 (4) Jun 01, 2015
that's why your eu and the ee's there have built so many fusion reactors that are powering the nation, right?

your claims are like every other claim you've made re: eu
unsubstantiated conjecture based upon conspiracy and delusional beliefs
not science

just because you believe in something doesn't make it true
eu is PSEUDOSCIENCE
that is why you've not built nuclear reactors or been able to get noticed by actual scientists


You clearly do not understand how science is progressed. You are entranced by the emperor's old garb, which is growing haggard and torn. You preach and polish your robes of the standard model, not noticing that like a faded supermodel well past her prime that beauty is fleeting. Bang your gavel all you want and pontificate to your heart's content. Irregardless the current of change flows past you on the river of time.
cantdrive85
1.8 / 5 (5) Jun 01, 2015
that's why your eu and the ee's there have built so many fusion reactors that are powering the nation, right?


It's funny you bring that up Cap'n Stoopid. You must not be aware of Eric Lerner ( author of 'The Big Bang Never Happened') and his Lawrenceville Plasma Physics operation. He only has developed the most promising form of fusion, aneutronic fusion using the dense plasma focus. Your statement may be true very soon, much sooner than ITER or many of the other weak attempts using those same old theoretical plasma physics that lead to continual failure after failure.

http://lawrencevi...ics.com/
Captain Stumpy
5 / 5 (3) Jun 02, 2015
You clearly do not understand how science is progressed
@stevepig
better than you do
i require evidence, not faith based conjecture and pretty pictures

Lawrenceville Plasma Physics operation
@cd
i know OF it
He only has developed the most promising form of fusion
it aint working yet though, is it?
still waiting for RESULTS, like everything else
using the dense plasma focus
still assuming that astrophysicists are not using plasma physics?
it was posted here on PO that Lerner himself said MHD does the job for the most part and is not invalidated, despite your claims
when i get that link, i will repeat it here for you
using those same old theoretical plasma physics
what is theoretical about PPPL?
http://pppl.gov/

NOTHING
it is simply that YOU refuse to accept proven physics and validated plasma physics
(like magnetic reconnection)

feel free to refute: you still haven't given ANY evidence

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