Planetary accretion in the inner Solar System

alexblackwell · Jul 19, 2004

From the July 15, 2004 issue of Earth and Planetary Science Letters: Planetary accretion in the inner Solar System John E. Chambers Earth Planet. Sci. Lett. 223, 241-252, (2004). For those without access to EPSL, this paper, which is part of the EPSL Frontiers series, is freely available (~262 Kb PDF reprint) for a limited time.

earthseed · Jul 21, 2004

Thanks, Alex. This is a well written paper. They suggest that formation of Earth's moon is a reasonably likely event, but they do not mention the formation of large bodies at the Lagrange points of a planet's orbit, as presented in this paper that you gave us during the last days of the old forums.

exoscientist · Jul 22, 2004

Thanks for the link. This reminds me of research on the position of planets at their formation and where they wind up: Moving the Orbits of Planets http://www.ifa.hawaii.edu/faculty/jewitt/kb/migrate.html This notes that present theories suggest some planets moved outwards while others moved inwards. There is also a paper on the outwards migration of Neptune in the August issue of Icarus. I wonder if this can explain the "faint-Sun paradox" in regards to the Earth and Mars. This is the problem that the Sun was supposed to be significantly fainter early in the life of the Solar System but both Earth and Mars show signs of liquid water carved channels at this early time. This is a big part of the justification for the viewpoint of some Mars scientists that Mars was cold and dry early in its history because theories that propose greenhouse heating under a thicker atmosphere have difficulty getting the required amount of heating. But perhaps the explanation lies in the possibility that these planets were closer to the Sun early on and that is what allowed them to have the extensive liquid water carved features. Bob Clark <div class="Discussion_UserSignature"> </div>

alokmohan · Jul 22, 2004

The planet formation theories keep on changing too many times.

earthseed · Jul 22, 2004

If the inner planets have moved outward from the sun, they should still be moving. What force is going to make them stop? This movement should be detectable with present technology. As far as I know there is no evidence for this, so I see no reason to believe it. And is there any evidence at all for an early warm wet period on Mars?

Saiph · Jul 22, 2004

The reason they'd move out is a weaking of the sun's gravity. The reason they'd stop, is the same reason a ball stops rolling when it goes uphill. The orbits will probably be made a bit more eccentric because of this. There is no evidence of this now, because the Sun is barely shedding any mass, the rate is negligible. However, if the sun loses a large amount of mass, this is a direct consequence of the conservation of energy laws. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

exoscientist · Jul 23, 2004

Steve, the question being wrestled with in the Neptune studies is why did it stop where it did? I believe the justification for why it moved and why it stopped where it did was because of complex gravitational interactions between the planets. It was long believed that Mars had a thicker atmosphere in its early history, the Noachian, because of the extensive water carved features. The MER missions are offering even further evidence this was the case. The problem is getting Mars warm enough in its present location even with greenhouse heating to explain the features we see. Bob Clark <div class="Discussion_UserSignature"> </div>

CalliArcale · Jul 23, 2004

Same here. I don't buy a wandering major planet, except perhaps the idea of a large extrasolar planet occasionally wandering close enough to perturb some stuff out of the Oort Cloud, though that's largely conjecture. Major planets trucking through the inner solar system, however, should have left dramatic orbital evidence. Minor planets are a different story, of course. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

Saiph · Jul 23, 2004

even in "chaotic" systems, you can predict major trends. They don't say where the planets are going to be exactly, like at perihelion. They merely say they're going to be further away, by ~X amount. Sorta like with global warming. Sure, we can't predict the hurricanes resulting from it. Only that there'll probably be more (or less) and other things are going to happen. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

exoscientist · Jul 23, 2004

"Major planets trucking through the inner solar system, however, should have left dramatic orbital evidence." Say like a Mars-sized planet plunging into the Earth? Bob Clark <div class="Discussion_UserSignature"> </div>

exoscientist · Jul 23, 2004

One fact that argues in favor of the migration of planets is the existence of "hot Jupiters" in extrasolar systems. When the first extrasolar planets were discovered astronomers were suprised that so many of these Jovian sized planets orbited so close to their stars. The prevailing theory is that they formed further out then migrated closer to their parent stars. Bob Clark <div class="Discussion_UserSignature"> </div>

earthseed · Jul 25, 2004

The Mars-sized planet plunged into the Earth while the planets were still forming. The system appears to have been stable since then. A "hot Jupiter" solar system is obviously very different from ours. I am not sure what lessons we can learn from it that apply to us. Obviously, Mars has had warm wet periods that produced the erosion features there. But as far as I know, the timing of these events is poorly known. Was there a long warm period near the beginning of Mars' life, or were these events of episodic flooding, possibly caused by comet impact or a period of sustained volcanic activity?

exoscientist · Jul 25, 2004

The systems with hot Jupiters are different from ours now.The theory is that they were similar to ours in the past until the planets gradually changed their positions. Bob Clark <div class="Discussion_UserSignature"> </div>

CalliArcale · Jul 25, 2004

<blockquote>In reply to:<hr />The Mars-sized planet plunged into the Earth while the planets were still forming. The system appears to have been stable since then. <hr /></blockquote> Additionally, computer models suggest that the Mars-sized object (assuming it existed; though the theory is plausible, it's hard to prove) would've had a surprisingly normal orbit -- that is to say, it wasn't some deep space interloper. It probably formed in a Sun-Earth lagrange point. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

Saiph · Jul 26, 2004

what, that large objects can have eccentric orbits? You can't accept that possibility? <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

Saiph · Jul 26, 2004

so what's this wandering planet notion you're denouncing, cause what you just posted sounds like what I'm familiar with. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

earthseed · Jul 26, 2004

I think stevehw33 is referring to exoscientist's suggestion that the climate of early Mars was warmer because it was then closer to the sun. I agree with steve in this case, I do not think there is any significant change occuring in the planetary orbits in this solar system. I wonder though, if orbits were changing, could we detect it with our current technology? I do not think that the "hot Jupiter" phenomenem in other solar systems has really been explained yet. It is assumed that the large planet formed out past the ice line, then moved closer to its sun. But what has stopped it from falling into the sun? I don't think the sun changed mass in this case.

exoscientist · Jul 26, 2004

Planetary migration in a planetesimal disk: why did Neptune stop at 30 AU? Icarus, Volume 170, Issue 2, p. 492-507. Abstract We study planetary migration in a gas-free disk of planetesimals. In the case of our Solar System we show that Neptune could have had either a damped migration, limited to a few AUs, or a forced migration up to the disk's edge, depending on the disk's mass density. We also study the possibility of runaway migration of isolated planets in very massive disk, which might be relevant for extra-solar systems. We investigate the problem of the mass depletion of the Kuiper belt in the light of planetary migration and conclude that the belt lost its pristine mass well before that Neptune reached its current position. Therefore, Neptune effectively hit the outer edge of the proto-planetary disk. We also investigate the dynamics of massive planetary embryos embedded in the planetesimal disk. We conclude that the elimination of Earth-mass or Mars-mass embryos originally placed outside the initial location of Neptune also requires the existence of a disk edge near 30AU. http://adsabs.harvard.edu/cgi-bin/bib_query?2004Icar..170..492G Types of extra-solar planets & how they got to be that way. March 2003 "why are the hot Jupiters so close to their stars? (19/105 planets have d < 0.25 au) the majority view planet forms far from the star (by condensation/accretion) & carves out a gap in the disk; perhaps other instabilities form in the disk? (e.g., a bar? spiral density waves? both of these are seen in spiral disk galaxies) in the disk also inner disk loses energy (viscosity) and transfers angular momentum to the outer disk; the inner disk falls onto star angular momentum is transferred from planet to outer disk or to instabilities in the disk: planet migrates toward star (migration time ~ 106 yrs) <div class="Discussion_UserSignature"> </div>

exoscientist · Jul 26, 2004

"I don't buy the wandering planets theories for the same reason Sagan & other astronomers rejected "World's in Collision' nonsense by Velikoff. I remember reading the thing in High shcool and after about 4 chapters of it realizing the man was delusional. There's just no support for it of any consequence. " You could use the same argument against the Moon forming by impact of a Mars-sized body to the Earth. Bob Clark <div class="Discussion_UserSignature"> </div>

earthseed · Jul 26, 2004

Thanks, exoscientist. There are a lot of interesting ideas here, such as there may have been previous generations of planets that fell into the sun. Or a Jupiter-like planet could migrate inward without necessarily ejecting or destroying the existing inner planets. Could the collision that produced our moon have been caused by a migrating previous-generation Jupiter? Still, it appears that all this chaos stopped soon after the solar system formed. The time scales in the papers you cited are all short. So I do not think planetary migration had any influence on the climate of Earth or Mars after about four billion years ago.

exoscientist · Oct 25, 2004

<blockquote>In reply to:<hr />Re: Planetary accretion in the inner Solar System [re: AlexBlackwell] Thanks for the link. This reminds me of research on the position of planets at their formation and where they wind up: Moving the Orbits of Planets http://www.ifa.hawaii.edu/faculty/jewitt/kb/migrate.html This notes that present theories suggest some planets moved outwards while others moved inwards. There is also a paper on the outwards migration of Neptune in the August issue of Icarus. I wonder if this can explain the "faint-Sun paradox" in regards to the Earth and Mars. This is the problem that the Sun was supposed to be significantly fainter early in the life of the Solar System but both Earth and Mars show signs of liquid water carved channels at this early time. This is a big part of the justification for the viewpoint of some Mars scientists that Mars was cold and dry early in its history because theories that propose greenhouse heating under a thicker atmosphere have difficulty getting the required amount of heating. But perhaps the explanation lies in the possibility that these planets were closer to the Sun early on and that is what allowed them to have the extensive liquid water carved features. Bob Clark<hr /></blockquote> A report to be presented to the Fall 2004 AGU meeting will argue that a Mars' orbit closer to the Sun may partially explained how Mars was able to remain warm enough for large scale water carved features to be formed early in its history: ====================================== 0800h AN: P21A-0211 TI: Mars Orbit and Temperature: Why and When an Early wet Mars AU: * Leubner, I H EM: ileubner@crystallizationcon.com AF: Rochester Institute for Fundame <div class="Discussion_UserSignature"> </div>

nexium · Jan 14, 2005

Here are two more possibilities with little probability and less evidence. Jupiter may have behaved like a proto star about two billion years ago instead of 4.6 billion years ago, warming Mars by about 50 degrees c and Earth about 20 degrees c at about ten year intervals. Jupiter has no ways near enough mass to sustain nuclear fusion so it cooled to it's present temperature after the contraction phase ended. Similar intermittent warming occured up to about two billion years ago when Sol's binary twin star left the Solar system. Neil

silylene old · Jan 15, 2005

Similar intermittent warming occured up to about two billion years ago when Sol's binary twin star left the Solar system. I would say that is a minority opinion. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

bobvanx · Jan 17, 2005

>>[proto-star Jupiter]...warming Mars by about 50 degrees c and Earth about 20 degrees c at about ten year intervals. Just the fact that Jupiter has icy moons would suggest this is unlikely. Mars is in conjunction with Jupiter every 2-1/2 years or so, as are we every 14 months or so. For infrared radiation from Jupiter's gravitational contraction to warm either of these planets much, it really would have to shine like a star. The temperature within the Jupiter system would have blasted those moons into cinders.

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