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Bjarne
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Why is the density of Mercury 40% larger than the density of Mars?
Bjarne said:All planets are made of the same dust, so the density "should" be the same.
( I do not believe that something have knocked off the surface of Mercury )
Off course also the inner heat and pressure de play a role for the density, do someone have a idea off how much?
But metal is created under pressure. That mean less mass = less metal.so i would expect that the first sizable objects to form in the early solar system would be metal
Bjarne said:Iron is so fare I understand produced inside a planet
But not metal heavyer than that
right ?
mgb_phys said:Why is still up in the air!
A similair thing happened to Earth forming the moon, the Earth's density is even high than mercury's and the moon is composed of Earth's early crust.
.
But not metal heavyer than that
Enthalpy said:Also my opinion, that lighter elements were blown away.
Also, denser elements tend to have a higher melting and boiling point, so a nearer Sun evaporates lighter ones.
Less mainstream: if at some epoch elements behave like a gas, then the Sun's (works with planets as well) gravity makes a wonderful elements and isotopes separator, with 30km/s speed instead of 300m/s in uranium enrichment. I like this one for explaining isotopic compositions of planets.
"Little" drawback: when, where, how should elements be gases?
Thus, since temperature increases towards the center of collapsing (sub)Nebulas, planetoids condense out of the gaseous phase from the outside in, from colder to hotter. Thus, Io (closest to Jupiter) is the densest Jovian moon, while Mercury (closest to Sun) is the densest planet. Just like Jupiter's Io, the Sun's Mercury condensed (millions of years ?) after Mars, the Moon, Earth & Venus. By that time, all the "lighter elements were blown away", precisely as you say. This left Mercury "under-massed" (less material left) and "over-dense" (it was mostly iron, nickel, and dense rocks).the characteristics of these worlds [= Jovian moons] are consistent with a decreasing average density with increasing distance from Jupiter, implying that the relative amount of water-ice crust increases w.r.t. the rock core... Jupiter must have been hotter in the past than it is today, [so] Io would have been close enough to have had most of its volatiles evaporate away. Moving progressively farther out, Europa would have been able to hold onto some water, Ganymede even more, and Callisto (being the coldest of the Galilean moons at the tie of its formation) would have retained the largest percentage of volatiles.
The consequences of this evolution can be seen in each of the Galilean moons. Consider them in sequence beginning with the one farthest from Jupiter. Callisto apparently cooled and solidified rapidly after material accreted out of the local Subnebula around Jupiter. As a result, its surface continued to collect dust as the nebula thinned, blanketing the moon w/ dark material. Having solidified in the early stages of the formation of the solar-system, Callisto was also subject to frequent impacts of the still-abundant objects that traveled among the newly formed planets and moons. Evidence of the nebular dust accretion and the impacts remains today.
Ganymede, solidifying somewhat more recently, has a newer surface than Callisto's*...
"Dust” in this context simply means microscopic bits of water ice, iron and other solid substances... Surrounding each star is a rotating disk of leftover material, the wherewithal for making planets. Newly formed disks contain mostly hydrogen and helium gas. In their hot and dense inner regions, dust grains are vaporized; in the cool and tenuous outer parts, the dust particles survive and grow as vapor condenses onto them.
Astronomers have discovered many young stars that are surrounded by such disks. Stars between one million and three million years old have gas-rich disks, whereas those older than 10 million years have meager, gas-poor disks, the gas having been blown away by the newborn star or by bright neighboring stars. This span of time delineates the epoch of planet formation. The mass of heavy elements in these disks is roughly comparable to the mass of heavy elements in the planets of the solar system, providing a strong clue that the planets indeed arose from such disks.
http://www.sciam.com/article.cfm?id=the-genesis-of-planets
The density of a planet is determined by its mass and volume. Mercury has a larger mass and smaller volume compared to Mars, resulting in a higher density.
Mercury has a mass of 3.285 x 10^23 kg, while Mars has a mass of 6.39 x 10^23 kg. This means that Mercury's mass is almost half of Mars' mass.
Mercury is significantly smaller than Mars in terms of volume. This means that its mass is more compressed, resulting in a higher density.
Yes, the composition of a planet plays a role in determining its density. Mercury is primarily composed of metal and rock, while Mars has a larger amount of lighter elements, such as iron oxide. This difference in composition contributes to the difference in density between the two planets.
Aside from mass and volume, other factors such as gravitational pull and temperature can also affect the density of a planet. However, these factors do not have a significant impact on the density difference between Mercury and Mars.