Was Mercury once a hot Jupiter?

  • Thread starter Crossover_Maniac
  • Start date
Status
Not open for further replies.
C

Crossover_Maniac

Guest
I was reading in Scientific American about research going into planetary atmospheric loss. According to the article, hot Jupiters (Jovian-size planets extremely close to their parent star), can't be too old otherwise they would lose their atmosphere. So, the question is, in the early days of the solar system, was Mercury a gas giant and the Mercury we see today is the solid core left over after it lose its hydrogen and helium atmosphere.
 
V

vogon13

Guest
Sorry, no.

It would be fun to have a local (safe) gas giant core to play with, but Mercury ain't it.

Some speculation exists that perhaps Mercury did lose quite a bit of crust/mantle from a largish impact long ago, but not 100+ earth masses. More like ~~.1.

Mars seems to have a major hit in it's northern regions, and we have the Orpheus impact here to conjecture about.
 
A

aphh

Guest
Also, Hot Jupiters have likely migrated so that their orbit once had a lot larger radius. When closing their distance to the parent star hot jupiters ate pretty much everything on their way that existed around the star.

Had our Jupiter decided to become a hot jupiter, there would likely be no Mercury and no Earth today.
 
Z

ZenGalacticore

Guest
I agree with the above posters. But I've often thought that maybe Mercury was once a moon of Venus and in some unknown cosmic disturbance or event, was ripped out of Venus' orbit. Maybe that's why Venus rotates in a retro-grade motion, the only planet that rotates clockwise when viewed from the N. Pole.

[edited for typo]
 
M

MeteorWayne

Guest
That seems very unlikely. Mercury is far too massive, and of different composition than Venus. Mercury is a very dense object, unique in the Solar syatem.

I know this is a duplicate subject, but haven't found the other one yet.
 
3

3488

Guest
MeteorWayne":1d47zehn said:
That seems very unlikely. Mercury is far too massive, and of different composition than Venus. Mercury is a very dense object, unique in the Solar syatem.

I know this is a duplicate subject, but haven't found the other one yet.
Very true Wayne.

Mercury is fundementally different in this respect. The size & mass of the iron core, now thought to be dual layered in relation to the overall size & mass of Mercury is unique.

Mercury is certainly not a core of a vaporized hot Jupiter, that much is for certain. The recent MESSENGER passes in January 2008 & October 2008 have shown Mercury to be far more complicated than thought before. Layered differing types of lava, andesitic types interwoven with regular basalts, increased iron concentrations on the floor of Remrandt Basin, shield volcanoes, other volcanic features, rilles, etc. Turning out to be quite a place.

But certainly not an exposed core of a former gas giant.

Also a migrating Jupiter like world into that orbit would have scattered Venus, Earth & Mars & also Mercury is not close enough to the Sun to vapourize a Jupiter type world. Whilst at perihelion the solar incidence at Mercury is 11 times stronger than on Earth, still not enough to vapourize a Jupiter type world. Ice rich moons would not survive for long for sure, but the escape velocity of Jupiter is too high to allow gas to escape in large quantities.

Andrew Brown.
 
3

3488

Guest
vogon13":kupyq9gd said:
Sorry, no.

It would be fun to have a local (safe) gas giant core to play with, but Mercury ain't it.

Some speculation exists that perhaps Mercury did lose quite a bit of crust/mantle from a largish impact long ago, but not 100+ earth masses. More like ~~.1.

Mars seems to have a major hit in it's northern regions, and we have the Orpheus impact here to conjecture about.
Hi Vogon,

I have heard also that Mercury may have had an outer layer removed during a gigantic impact. I'm not sure, but who knows. I suspect Mercury is not a lot different in size & mass to the orginal body. IMO, Mercury's bulk density results from the location of it's formation close to the proto sun.

It has also been speculated that the Mars Phoenix Lander had landed within the area of the gigantic hypothesized Martian northern hemisphere impact basin.

Andrew Brown.
 
N

neilsox

Guest
I feel the urge to be contrary. How about a Neptune mass "hot Jupiter" that formed near the present orbit of Venus, then migrated inward. A stronger solar wind could? sweep away the hydrogen and other gases, leaving about 1% = the mass to be the Mercury of today, with a somewhat more circular orbit than it had when it was losing it's gas. Do we really know that gas giants always have less than 1% heavy metals? This could have happened 4.4 billion years ago, leaving lots of time for Mercury to get it's present appearance? Neil
 
3

3488

Guest
Hi Neil,

Myself I doubt that Mercury is the exposed core of anything. IMHO, Mercury formed more or less the way it is now, due to the location within the protoplanetary nebula close to the protosun.

There is speculation that perhaps a layer was blasted off, but I'm not so sure. True Hermean rocks would have blasted into space by large impacts like those that formed the Caloris, Tolstoj & Rembrandt basins.

I still think the general physiology of Mercury of today is similar to the original planet, before it got pummelled & roughly 40% of the surface was flooded by lava.

Tremendous heat would have melted the original crust when the core differentiated out from the silicate rock, then perhaps a second time when the core itself differentiated into an outer & inner one (perhaps a near pure iron inner one with some nickel & an iron sulphide outer one with radioactive isotopes, which is churning over creating the magnetosphere).

That's my tuppence worth.

Andrew Brown.
 
D

dangineer

Guest
I'm not countering anyone's post, but I would like to point out that most of the exoplanets found thus far are hot Jupiters. However, this is only because these types of systems are far easier to detect. It could very well be that most planetary systems are very similar to our own - with several small rocky planets near the star and gas planets towards the edge. These types of systems are just more difficult to detect. With the new planet searching technology that's being developed and coming online, our picture of the galaxy's planet distribution may change dramatically, though, as we will be able to detect ever smaller worlds.
 
K

kelvinzero

Guest
Maybe I am missing something.

I was interested in all the discussion of the composition of mercury itself because I was trying to spot how it compared to what we expect the core of a hot jupiter to be.

Are the orbital arguments the only points in this thread actually going towards disproving that mercury was a hot jupiter?
 
D

dangineer

Guest
I do believe another observationwhich makes it unlikely that Mercury was a hot Jupiter is the apparent age of it's crust. Some parts of it appear incredibly old, while other parts appear much younger. The younger parts support the impact hypothesis, but the old parts would discount any hot Jupiter hypothese. If it was once a hot Jupiter, it would require a significant amount of time before it finally withered away and exposed its surface to asteroid and comet impacts. This would make Mercury's surface appear very young, but most observations show some parts are very old - too old to support this idea.
 
3

3488

Guest
I agree dangineer.

Much of Mercury does appear much too old to be from a remnant core of a former gas giant.

Also as I said, there would have been volcanism from the heat generated from the core, mantle, crust seperation, then perhaps a slightly later episode when the core itself differentiated.

Mercury is not a core of a former gas giant, in fact IMO all evidence points to Mercury being more or less the same size & mass since formation, in the inner regions of the protoplanetary nebula.

About 40% of Mercury is covered by lava plains, most of the rest is fairly heavily cratered (though not unformily). Also there appears to be a region of 30% of the surface being generaly smoother, with a similar amount being heavily cratered, suggesting that perhaps Mercury was one Sun synhronous, i.e did at one time keep the same side facing the Sun, with the smoother terrain being the former trailing side & the more cratered area leading??

If we are going down the erroneous route of Mercury once being a core of a former gas giant (IMHO), than why not suppose that Venus, Earth & Mars are also exposed cores of former gas giants???

It does not stand up to closer scrutiny.

Andrew Brown.
 
K

kg

Guest
What would one expect to see if you took away Jupiters' atmosphere?
 
Z

Zarpheous

Guest
Could Mercury possibly be the remains of an asteroid that collided with a planet in our solar system?
 
M

MeteorWayne

Guest
Highly unlikely.

First, it's far bigger than any asteroid, and second, there's no way for something coming from the asteroid belt to wind up in Merecury's orbit.
 
S

SpaceXFanMobius57

Guest
I would like ao amplify Kgs question and ask what would the core be like if we completely took away Jupiters atmosphere.
 
Y

yevaud

Guest
Well, there is some good theory that the cores of Jupiter and Saturn are degenerate hydrogen and helium, literally a liquid metal under extreme pressure.
 
N

neilsox

Guest
Assuming liquid degenerate metal = hydrogen and helium are 80% of the core of Jupiter and Saturn, the pressure at the surface of the core would decrease from about a billion psi to zero with all the atmosphere gone, including most of the degenerate hydrogen and helium as they would revert back to ordinary hydrogen and helium at low pressure. The 20% would remain, but we can't even guess what the ratios of the elements would be. I presume some of the fine dust of heavy elements, presently in the atmosphere would form the crust on the remaining 20% of the Mercury size core.
Since Saturn has about half the average density of Jupiter, Saturn's core would (and is) likely be much smaller than Jupiter's core. Neil
 
H

hammerit

Guest
I have heard it postulated that the core of gas giants could possibly be made of diamond.The temperature and pressure is great enough for carbon to compress into it I suppose.Whatever the true core of a gas giant is I think it would be less dense per volume than a terrestrial planet.Mercury seems to me to be a stripped planet it has more core than crust.Did some colossal colission in the past strip the crust away?
 
Status
Not open for further replies.

ASK THE COMMUNITY