Planet Mercury: Facts about the planet closest to the sun

[Admin]

Mercury is the smallest planet in our solar system and is known for its short years, long days, extreme temperatures and weird sunsets.

Planet Mercury: Facts about the planet closest to the sun : Read more

 

[Emely Morris]

Many people think that Mercury is the hottest planet in the solar system because it is closer to the Sun than other planets. However, Venus is the real record holder in this matter. The surface of Mercury, which faces the Sun, heats up to 427 ° C, while the opposite side of the planet can be as low as -173 ° C. This is due to the fact that the planet does not have a dense atmosphere to regulate temperature.

 

[Catastrophe]

Quick skim, so I may have missed it but . . . . . .

"Mercury is the second densest planet after Earth, with a huge metallic core roughly 2,200 to 2,400 miles (3,600 to 3,800 kilometers) wide, or about 75% of the planet's diameter."

. . . . . . . . . isn't the theory that an early impact blew off a lot of the mantle, leaving this large core?

Cat

 

[rod]

"The Sumerians also knew of Mercury since at least 5,000 years ago. It was often associated with Nabu, the god of writing, according to a site connected to NASA's MESSENGER mission."

From different archaeology reports I read, the Sumerians held to the view the earth was a flat disk with solid dome above it that contained the Moon, Sun, planets, and stars. This is represented on various clay tablets uncovered. The Babylonian creation story (Enuma Elish) also features concepts like this too. There are some groups today who teach this geocentric view. When it comes to explaining the origin of Mercury, Venus, Earth, and Mars, the solar nebula and spinning accretion disk is not an easy model to show their origins. Exoplanet studies today are finding thousands of exoplanets that range in size from about 1 to 3 earth radii and orbit very close to their parent stars. Such systems give headaches to explain their formation and origin. Our solar system configuration stands out sharply by comparison.

Did nature or nurture shape the Milky Way's most common planets?, https://phys.org/news/2021-08-nature-nurture-milky-common-planets.html

"A Carnegie-led survey of exoplanet candidates identified by NASA's Transiting Exoplanets Satellite Survey (TESS) is laying the groundwork to help astronomers understand how the Milky Way's most common planets formed and evolved, and determine why our solar system's pattern of planetary orbits and sizes is so unusual."

My observation. http://exoplanet.eu/, presently shows 2121 exoplanets listed with radii 1 to 3 earth radii size. An example of exoplanets studied with radii some 1 to 3 earth radii size, TOI-431/HIP 26013: a super-Earth and a sub-Neptune transiting a bright, early K dwarf, with a third RV planet, https://ui.adsabs.harvard.edu/abs/2021arXiv210802310O/abstract, August 2021.

My note. The arXiv paper, https://arxiv.org/pdf/2108.02310.pdf, 21 page report dated 06-August-2021. "Table 1. Details of the TOI-431 system." TOI-431 is shown as mv + 9.12 and distance 32.61 pc. On page 19, "Table A1." shows the host star is 0.81 solar mass and 0.72 solar radii size. The orbital period for the 3 exoplanets reported range 0.49 days - 12.46 days. Exoplanet systems like this documented by TESS are a challenge to explain using the gas cloud and protoplanetary disk model(s). Our solar system does not have planets like this orbiting the Sun. The radii sizes reported here range from 1.28 earth radii to 3.07 earth radii. All very close to the parent star and all with very short orbital periods. The phys.org report opens, "A Carnegie-led survey of exoplanet candidates identified by NASA's Transiting Exoplanets Satellite Survey (TESS) is laying the groundwork to help astronomers understand how the Milky Way's most common planets formed and evolved, and determine why our solar system's pattern of planetary orbits and sizes is so unusual." I find this a very good observation concerning exoplanet studies. Our solar system is not the norm in the Milky Way.

 

[sam85geo]

I understand that when main sequence stars like the Sun "turn on" the heaver elements like iron remain "close in" to the star while the gaseous and lighter elements are blown farther away. Ref: T Tauri wind. Thus, Mercury due to its distance from the Sun should be very dense and have a large metallic core.

 

[Catastrophe]

sam85geo, do you favour that over impact? Or what about and/or?

Cat

 

[rod]

sam85geo et al. It should be pointed out that planet formation scenarios are fraught with difficulties in the calculations. Here is a recent example of dust and gas quantities.

The dust and gas in protoplanetary disks, https://phys.org/news/2021-08-gas-protoplanetary-disks.html

Reference paper, Investigating the Relative Gas and Small Dust Grain Surface Heights in Protoplanetary Disks, https://iopscience.iop.org/article/10.3847/1538-4357/abf92e, 04-June-2021.

The NASA ADS Abstract is Investigating the Relative Gas and Small Dust Grain Surface Heights in Protoplanetary Disks, https://ui.adsabs.harvard.edu/abs/2021ApJ...913..138R/abstract, June 2021. The arXiv paper https://arxiv.org/pdf/2104.07821.pdf, 19-April-2021, 13 pages.

My note. In the arXiv paper, "Table 1. Gas Disk Parameters" shows some properties of the stars. Masses range 1 to 2.5 solar masses and ages range 1.1 to 6.03 million years old, thus considered very young stars. Distances range 101 pc to 184.4 pc. Table 4 indicates 0.2 mass of star for the mass of the disk around the star HD 97048, listed as 2.5 solar mass star. The protoplanetary disk mass then is about 167,000 earth masses. Page 9, figure 2 shows Mgas = 0.01 Mstar for 1 solar mass star. This is 3330 earth masses. This could lead to a total gas and dust mass of 330,000 earth masses for a one solar mass star. In my studies on protoplanetary disk masses, it is difficult to pin down the exact masses claimed for various stars studied. Quite a range of mass are reported using earth masses for dust and gas in the disks reported. Using the protoplanetary disk model for exoplanet origins, it is clear that various disks reported have many different dust and gas mass ratios and a wide variety of total disk mass reported. This makes for a random, chaotic formation of any exoplanets, thus neat claims for our solar system origin, have many documented examples now in exoplanets that challenge various assumptions including the formation of the terrestrial planets around the Sun. If Mercury was easy to show how it formed, then TOI-431 b would be easy to explain too. However, we have no such planets orbiting the Sun here like this. This planet has a mean density some 8 g cm^-3.

 

[Catastrophe]

sam85geo

Wiki: "Their central temperatures are too low for hydrogen fusion. Instead, they are powered by gravitational energy released as the stars contract, while moving towards the main sequence, which they reach after about 100 million years."

Where does the Fe come from?

Cat

 

[rod]

sam85geo

Wiki: "Their central temperatures are too low for hydrogen fusion. Instead, they are powered by gravitational energy released as the stars contract, while moving towards the main sequence, which they reach after about 100 million years."

Where does the Fe come from?

Cat

Cat, sam85geo et al. Fe in the protoplanetary disk that is used to explain the origin of the planets in our solar system must be seeded by past generations of stars using the r-process and s-process in stellar evolution. This gets into some very interesting stuff concerning meteorites and various elements found in them, also how planets like TOI-431 b did not form orbiting our Sun. Chaos and catastrophism is invoked to explain along with past generations of stars - no longer observable using telescopes today

 

[rod]

FYI. My summary here. To explain various elements we see on Earth and Mercury today (iron is an example), past generations of stars seeded the protoplanetary disk and solar nebula before the planets formed, seeded by past generations of stars we cannot see using telescopes today. Super-earths and sub-Neptunes pose challenges to show how Earth, Venus, and Mercury formed while super-earths and sub-Neptunes around the Sun did not. Observations of various disks reported around young stars today, shows great variety in sizes and disk masses.

Somehow, out of all this chaos, random collisions, and mixed martial art planet formation scenarios, we appeared here today reading about all of these interesting finds in astronomy

 

[Catastrophe]

Rod, of course I am aware of the presence of "metals" as in anything heavier than H and He in the protoplanetary disc. . I was looking at sam85geo's post which contained: "I understand that when main sequence stars like the Sun "turn on" the heaver elements like iron remain "close in" to the star while the gaseous and lighter elements are blown farther away." Post #5.
Then you have my quote "Their central temperatures are too low for hydrogen fusion." Post #8.
Are these compatible? Can you account for the Fe described as being from the protoplanetary disc?
And the conclusion of Post #5: "Thus, Mercury due to its distance from the Sun should be very dense and have a large metallic core."
Is there some confusion here about T Tauri?

Cat

 

[rod]

Rod, of course I am aware of the presence of "metals" as in anything heavier than H and He in the protoplanetary disc. . I was looking at sam85geo's post which contained: "I understand that when main sequence stars like the Sun "turn on" the heaver elements like iron remain "close in" to the star while the gaseous and lighter elements are blown farther away." Post #5.
Then you have my quote "Their central temperatures are too low for hydrogen fusion." Post #8.
Are these compatible? Can you account for the Fe described as being from the protoplanetary disc?
And the conclusion of Post #5: "Thus, Mercury due to its distance from the Sun should be very dense and have a large metallic core."
Is there some confusion here about T Tauri?

Cat

Yes Cat, you are correct for pointing this out about iron and T Tauri stars. T Tauri stars with disks are not creating their own iron, gold, or uranium, anymore than the solar nebula model for the Sun and planets creates these elements in the disk by the Sun. Such elements must be mixed in from other sources postulated, thus the r-process and s-process. We can see various elements in planetary nebula like M57 in Lyra or M1 SNR in Taurus. The same applies for Betelgeuse. Betelgeuse reported iron/hydrogen is 0.05 dex, thus about 1.12 solar value (the Sun is 1.0 here) and if the star is some 16.5 solar masses, perhaps it contains more than 86,000 earth masses of iron. Betelgeuse - Wikipedia

Getting that iron to recombine into other earths and mercury like planets is more difficult than said

 

[Helio]

Many people think that Mercury is the hottest planet in the solar system because it is closer to the Sun than other planets. However, Venus is the real record holder in this matter. The surface of Mercury, which faces the Sun, heats up to 427 ° C, while the opposite side of the planet can be as low as -173 ° C. This is due to the fact that the planet does not have a dense atmosphere to regulate temperature.

Yes, Venus is about 15 to 20 deg. C hotter than the sunny side of Mercury.

But the hottest spot in the system is on Io due to its magma flows.

 

[sam85geo]

@Cat and Rod: I'm basically a simple soul that thinks whatever is most direct, mechanical and straight forward is in all probability accurate. My concept is that ~5B years ago a nearby supernova seeded and condensed interstellar gas and dust into what would become our Sun and planetary disc. That's where the iron in the inner planets comes from. It just seems to me that our Sun may have, could have, did distribute heavier elements like iron closer in ,and lighter elements farther out. The analogy is an explosion where lighter matter like dirt travels farther than heavier matter like rock. I don't know if an impact could have blown Mercury's mantle away; I hadn't heard that theory, but such is possible, re: Earth took "a hit" which tilted the planet 23.5 degrees, and gives us the seasons we experience. The T Tauri wind may or may not have happened; however, the solar wind just seems to me less likely to have effected the current planetary distancing. Thank you, this is a fascinating discussion.

 

[Helio]

I understand that when main sequence stars like the Sun "turn on" the heaver elements like iron remain "close in" to the star while the gaseous and lighter elements are blown farther away. Ref: T Tauri wind. Thus, Mercury due to its distance from the Sun should be very dense and have a large metallic core.

Yes. This heavier element will not be blown outward by a young star's winds as easily as the lighter elements.

Further, iron is abundant with only carbon, oxygen and nitrogen being significantly greater, ignoring the non-metals (H & He). [see here.]

Iron is unique. It is the last element that releases energy when it is formed by fusion, which helps more fusion of it. Fusion thereafter absorbs energy, which greatly restricts formation of heavier elements. Supernovae are needed for the heavier elements, and its the fusion of iron due to core temperatures and pressures that trigger a supernova (Type II).

My guess is that impacts and migrations are the key to understanding the large iron core of Mercury, in addition to more iron in the inner disk.

 

[Catastrophe]

Fe Iron is the last element produced within a star. It will be produced in the core, where any iron should reside. Is this not the case? It is not residing near the surface? So it is not available to be distributed by the solar wind until or if the star explodes. At least that's what I think, but I could be wrong.
Any iron from the protoplanetary nebula should have migrated to the core? So at this stage in the Sun's life Fe is not available to migrate to Mercury. I have never heard of Fe becoming available externally (e.g., from local supernova) during the Sun's middle years, or even earlier, but that means nothing, as I have not heard of most things.
I must admit that I am biased towards the collision theory (model) as most planets in the Solar System seem to have been hit at some time or other - probably during the Late Heavy Bombardment. Earth's Moon, Venus' backward rotation, Uranus on its side . . . . . . . . .

Cat

 

[Helio]

Fe Iron is the last element produced within a star. It will be produced in the core, where any iron should reside. Is this not the case?

Yes, but only the really massive ones that allow all those stages in fusion.

Of course, the protostellar disk will have lots of iron due to the spewing of supernovae into our region over those billions of years.

It is not residing near the surface? So it is not available to be distributed by the solar wind until or if the star explodes. At least that's what I think, but I could be wrong.

The convective layers of stars -- small ones are fully convective -- will keep the larger elements from sinking into the core. Thus we can see over 25,000 different absorption lines from light from the photosphere, which includes a host of elements and some molecules (e.g. TiO).

Any iron from the protoplanetary nebula should have migrated to the core? So at this stage in the Sun's life Fe is not available to migrate to Mercury. I have never heard of Fe becoming available externally (e.g., from local supernova) during the Sun's middle years, or even earlier, but that means nothing, as I have not heard of most things.

Jeff Hester (et. al.) discovered Fe60, which suggests a supernova was in our area not that long ago, but I don't recall how long ago.

I must admit that I am biased towards the collision theory (model) as most planets in the Solar System seem to have been hit at some time or other - probably during the Late Heavy Bombardment. Earth's Moon, Venus' vackward rotation, Uranus on its side . . . . . . . . .

Yes, the best models we have include some pretty crazy migration stunts.

 

[Catastrophe]

Helio, thanks for the correction. I had not allowed for convection. However, I am still a collision freak - I would have to be with a handle like mine.

Cat

 

[rod]

Well, a lively discussion by Helio, Cat, and sam85geo here Here are some additional reports and problems known concerning the formation of the inner solar system around our Sun.

Examining Initial Conditions of Planetary Formation Simulations, https://ui.adsabs.harvard.edu/abs/2019AAS...23325509D/abstract, January 2019. My observation. Different computer simulations to create the inner planets of the solar system run into different problems. This statement I found very interesting in the abstract. "However, we find that even under extreme pebble fluxes (2000 Earth masses per Myr) there isn't enough growth to recreate the inner Solar System." Other models reported are using 2 to 4 earth masses for the region 0.7 au to 1.2 au and still have problems reported in creating the inner planets of the solar system as well as timing of the giant impact with Theia to make the Moon.

Constraining the Formation of the Four Terrestrial Planets in the Solar System, https://ui.adsabs.harvard.edu/abs/2019ApJ...883..130L/abstract, October 2019. “To reproduce the orbits and masses of the terrestrial planets (analogs) of the solar system, most studies scrutinize simulations for success as a batch. However, there is insufficient discussion in the literature on the likelihood of forming planet analogs simultaneously in the same system (analog system). To address this issue, we performed 540 N-body simulations of protoplanetary disks representative of typical models in the literature. We identified a total of 194 analog systems containing at least three analogs, but only 17 systems simultaneously contained analogs of the four terrestrial planets. From an analysis of our analog systems, we found that, compared to the real planets, truncated disks based on typical outcomes of the Grand Tack model produced analogs of Mercury and Mars that were too dynamically cold and located too close to the Venus and Earth analogs. Additionally, all the Mercury analogs were too massive, while most of the Mars analogs were more massive than Mars. Furthermore, the timing of the Moon-forming impact was too early in these systems, and the amount of additional mass accreted after the event was too great."

Can narrow discs in the inner Solar system explain the four terrestrial planets?, https://ui.adsabs.harvard.edu/abs/2020MNRAS.496.3688L/abstract, August 2020. My observation. I find this a refreshing statement in solar nebula and accretion disk modeling. "Furthermore, the Venus-Earth pair was not reproduced in orbital-mass space statistically. Overall, our results suggest serious problems with using narrow discs to explain the inner Solar system. In particular, the formation of Mercury remains an outstanding problem for terrestrial planet formation models." The 25-page arXiv PDF report link, https://arxiv.org/ftp/arxiv/papers/2006/2006.02637.pdf

Isotopically distinct terrestrial planets via local accretion, https://ui.adsabs.harvard.edu/abs/2021Icar..35414052M/abstract, January 2021. My observation. Simulations attempting to create the terrestrial planets in our solar system have many issues documented in the models. The arXiv paper shows simulations with times 1 Myr, 5 Myr and out to 150 Myr timelines. The paper reports on simulations creating planet embryos, not full size planets as we see today in the solar system.

The Effect of a Strong Pressure Bump in the Sun's Natal Disk: Terrestrial Planet Formation via Planetesimal Accretion Rather than Pebble Accretion, https://ui.adsabs.harvard.edu/abs/2021ApJ...915...62I/abstract, July 2021. Reference paper link, The effect of a strong pressure bump in the Sun’s natal disk: Terrestrial planet formation via planetesimal accretion rather than pebble accretion, https://arxiv.org/pdf/2105.01101.pdf, 05-May-2021. 28-page arXiv report. My note. The 28-page report as with others show problems in simulations using accretion disks to make our solar system and inner planets like Mars, Earth, Venus, and Mercury. The computer simulation in this paper does not create full grown Earth planets but smaller sizes. The inner disk gas and dust mass is about 3 earth masses, otherwise problems develop for explaining the planets we see in the solar system today.

Reports like these fit well with my post #10 and #12 comments.

 

[Catastrophe]

Rod,
Errrr . . . . . . . . . . . . . . . is that a yes or a no?

(To collisions, especially Mercury?)

Cat

 

[Catastrophe]

The answer may lie in the type of giant impact — or impacts — that Mercury endured shortly after forming about 4.5 billion years ago. ... Such a collision might have created the planet Mercury, as well as Mars, and at least some of the larger asteroids such as Vesta and Psyche.6 Jul 2014
Did Huge Impact Shape Planet Mercury? | Space

What Is Mercury Made Of?

Mercury is a terrestrial planet with a rocky surface and metallic core.

www.space.com

Cat

 

[Catastrophe]

Did 26Al and impact‐induced heating differentiate Mercury ...
https://onlinelibrary.wiley.com › doi › full › maps
by GK Bhatia · 2017 · Cited by 6 — Mercury is distinct from the other terrestrial planets because of its large dense iron core which was estimated to be around 53–78% of its ...

"The majority of our models would require impact-induced mantle stripping of Mercury by hit and run mechanism with a protoplanet subsequent to its differentiation in order to produce the right size of mantle. However, this can be avoided if we increase the Fe-Ni-FeS contents to ~71% by weight."


Cat

 

[rod]

Cat, Mercury's surface shows many craters mostly small, thus collisions are apparent on the surface. However, your sources do not show the full details and problems for Mercury formation or the inner solar system planets. I find that a big problem when these models are reported to the public. The papers I cite show the computer details and there are many problems not clearly documented to the public.

Dynamical Avenues for Mercury's Origin. II. In Situ Formation in the Inner Terrestrial Disk, https://ui.adsabs.harvard.edu/abs/2021AJ....162....3C/abstract, July 2021. "Modern terrestrial-planet formation models are highly successful at consistently generating planets with masses and orbits analogous to those of Earth and Venus. In stark contrast to classic theoretical predictions and inferred demographics of multiplanet systems of rocky exoplanets, the mass (≳10) and orbital period (≳2) ratios between Venus and Earth and the neighboring Mercury and Mars are not common outcomes in numerically generated systems. While viable solutions to the small-Mars problem are abundant in the literature, Mercury's peculiar origin remains rather mysterious. In this paper, we investigate the possibility that Mercury formed in a mass-depleted, inner region of the terrestrial disk (a < 0.5 au). This regime is often ignored in terrestrial-planet formation models because of the high computational cost of resolving hundreds of short-period objects over ∼100 Myr timescales. By testing multiple disk profiles and mass distributions, we identify several promising sets of initial conditions that lead to remarkably successful analog systems. In particular, our most successful simulations consider moderate total masses of Mercury-forming material (0.1-0.25 Earth masses). While larger initial masses tend to yield disproportionate Mercury analogs, smaller values often inhibit the planets' formation as the entire region of material is easily accreted by Venus. Additionally, we find that shallow surface density profiles and larger inventories of small planetesimals moderately improve the likelihood of adequately reproducing Mercury."

No accretion disk models are fully explaining the origin of the inner solar system planets or showing how they grow from tiny dust grains to full grown, mature planets and we see now more problems in exoplanets studies with the large population of super-earths and sub-neptunes orbiting among many stars. The field of inner solar system planet building is fraught with uncertainties in the computer simulations and this should be clearly documented to the public. My observation. The 20 page arXiv paper, https://arxiv.org/pdf/2104.11252.pdf. "Table 1. Summary of initial conditions for our various simulation sets. The columns are as follows: (1) the number of simulations in each set, (2) the inner disk component’s inner edge, (3) outer edge, (4) total mass, (5) surface density profile power law and (6) ratio of total embryo to planetesimal mass (R). In all simulations, the inner disk is comprised of 20 embryos and 200 planetesimals, while the outer disk extends from the inner disk’s outer edge to 1.0 (top set of simulations) or 1.1 au (bottom set), and contains 40 embryos and 400 planetesimals with Mtot = 2.0 M⊕ and R = 4."…"3.5. Preferred disk structure Our simulations lead us to favor an inner disk component of moderate total mass, shallow slope, and low to moderate R. Additionally, we find that mass depletion interior to 0.75 au (rather than 0.6 au) tends to boost the probability of forming a successful Mercury-Venus system. A sample of eight systems that simultaneously satisfy criteria A, B and C is plotted in figure 7. An example of a successful evolution of one of these systems (the one depicted in panel six of figure 7) is plotted in figure 8. The system begins with Mtot = 0.1 M⊕, α = 1.0 and R = 4. Venus and Earth grow rapidly from seed embryos near the center of the disk at aV,o = 0.69 and aE,o = 0.87 au. By t = 2.8 Myr Venus attains half its ultimate mass. Similarly, Earth grows to 50% of its final size in 4.8 Myr. However, the evolution of the two larger planets subsequently bifurcate as Venus continues to rapidly accrete embryos and planetesimals from both the outer and inner disk in a manner such that it attains 80% of its eventual mass at t = 12 Myr. Conversely, Earth slowly grows to ∼65% of its ultimate size before experiencing a final giant impact with a 0.19 M⊕ protoplanet originally seeded at 0.97 au at t = 25.4 Myr (we note that these divergent accretion histories are a reasonable example of the scenario proposed by Jacobson et al. 2017, that aims to explain Venus’ lack of an internally generated magnetic field and natural satellite)."

My note. Simulation reports like this show the ongoing problems in the accretion disk model used to explain the origin of our solar system. The planets Mercury, Venus, Earth, and Mars all have various issues documented now in the computer models. The public should be told more about problems like this I feel in the accretion disk models used to explain our origins in science today. It seems many popular science sources fail mission here in my opinion.

 

[Catastrophe]

List of largest craters in the Solar System - Wikipedia
https://en.wikipedia.org › wiki › List_of_largest_craters...

Body	Crater	Crater diameter	Body diameter
Mercury	Caloris	1,550 km (963 mi)	4,880 km
Mercury	Rembrandt	715 km (444 mi)	4,880 km
Venus	Mead	280 km (170 mi)	12,100 km

I would not call Caloris small. Not that I would expect to see any size crater from a Mercury impact. that could rob it of part of its mantle.

Where is the crater left by formation of the Moon?

Cat

 

[sam85geo]

After partially wading through these last discussions this AM, two salient facts "stare out " at me, (as I'm "out of time"). 1. I've just got to get a updated Astronomy text. And 2. We humans are astronomically fortunate to be here "gossiping about" poor old Mercury. Again my thanks folks; very informative content.