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what evidence do we have that the asteroids indeed formed at the same time as earth? It depends on what is your definition as "the same time". The formation of the solar system and Earth did not happen at a particular second in time but was rather a continuous process. It also depends on what you define as "asteroids". I'll try to put some things in order. ...


12

The formation of a T-Tauri star spells the beginning of the end of the protoplanetary disk from which planets and asteroids can form. The end is nigh when that star ignites. The large solar winds and solar radiation pressure sweep the disk clean of all small objects. Some spirals inward, some outward. There's no dust and no gas from which new planets and ...


11

The formation and break up of supercontinents have happened throughout Earth's history in almost a cyclical manner. There may have been many others supercontinents before Pangaea and the total number of such is uncertain. The 4 last supercontinents are: Nuna (some other people call it Columbia) that was present in the period 2.0–1.8 Ga (billion years ago or ...


11

I can only answer the question of why is it mostly iron. Not too sure of the magnetic properties of iron versus nickel. As said in another answer, there is simply much more iron around than nickel. But the earth has also a large amount of other metals: silicon, magnesium, calcium, aluminium. So why is the core made of iron-nickel and not the other stuff? ...


10

why wouldn't that water evaporate on impact, and wouldn't the atmosphere at that time allow the vapours to escape Earth? The water would very likely evaporate on impact. However, gravity would prevent the gas phase water molecules from leaving Earth. The speed of a water molecule must be compared to the escape velocity of Earth (11 km/s) to determine ...


7

The main reason that there is more iron than nickel in the Earth's core, and in the universe generally, is that Nickel-56 beta-decays to Iron-56 (via cobalt-56). Much nickel-56 forms in Asymptotic Giant Branch stars and supernovae. However, nickel-56 decays with a half-life of 6 days. In nuclear fusion in stars, He-4 nuclei (alpha particles) form ...


6

So where did it go? Carbon was never there (or here) to begin with. You need to look at this from the opposite way. By asking "where did it go" you assuming the Earth was here first, with carbon, and then the carbon was removed somehow. But, Earth formed from a gaseous solar nebula that had all the elements. As the Earth-forming materials started ...


5

Did Jupiter really make Earth (in)habitable? Perhaps, but it's tough to tell. I wrote up an answer for a question on Physics getting at some more specific issues here; bear with me if I re-use a little bit of it. How is it physically possible for such a migration to occur? Planetary migration in the Solar System is described by the Nice Model (or, ...


5

You asked Why did all the land mass [Pangaea] form in one area? It didn't "form" in one area; the continents were simply joined together through the process of continental drift. To put it another way, the continents were formed in various locations before they were united - though the formation of continents never really stops. It seems to suggest ...


4

This is a very interesting topic that in the past several years has reached the spotlight because of the work of Robert Hazen on the concept of "mineral evolution". Minerals are basically just inorganic compounds: you take several elements, arrange them in certain ways and you get minerals. Thus, the minerals will be mostly determined by what's available to ...


4

On the earth as a whole, there is much more magnesium than aluminium. Your question is why, specifically in the crust, there is more aluminium than magnesium. The reason is that Mg is a compatible element whereas Al is an incompatible element. There were several questions here that addressed some aspects of this topic, for example: What are the high field ...


4

The giant impact hypothesis was not formulated to address the issue of how the Earth acquired its waters. At the time the giant impact hypothesis was formulated, the dominant theory for how the Earth acquired its waters was impacts by comets and wet asteroids during the late heavy bombardment. The giant impact hypothesis was instead formulated to address ...


4

I think this question is less intuitively obvious than it appears. and I like @Universal_learner 's answer. I thought I'd give a different approach to the question. Earth is the only object in the solar system with significant amounts of granite and granite is very important to your question because of it's durability and it's buoyancy. Granite forms ...


4

The age of 4.55Ga for the Earth is actually a date of "hard stuff" based on Iron-Nickel meteorites, dated using radio-isotope dating. If you had enough meteorite samples it should be possible to identify those with isotopes that imply a different age. For example, when plotted, their Pb isotope ratios will have different gradients. We do not see this.


2

I found the picture with a small write up on a JPL site. It's a picture of the Aine Corona with pancake domes. P-38340 MGN-48 5/21/91 This Magellan radar image shows a region approximately 300 kilometers (180 miles) across, centered on 59 degrees south latitude, 164 degrees east longitude and located in a vast plain to the south of Aphrodite ...


2

Many of your questions are answered in this question and associated answers: Why is Earth's age given by dating meteorites rather than its own rocks? To add to some of your other questions: Wouldn't radioactive decay have already been occurring in all of those meteorites long before they hit earth or our moon? Yes. We have an assumption that the ...


1

Not really. Assuming even minor igneous bodies differentiate (stocks), and that differentiation is basically a process of decantation of the solid magmatic phase (a process known as fractional crystalization) and fractionation of the fluid magmatic phase, virtually any solid mixture can differentiate. If you're not convinced, here's another argument. Let's ...


1

Minerals are naturally occurring chemical compounds composed of elements. Much of these elements were originally deposited with the earth saw formed. However, meteorites and asteroids have carried new mass onto the earth. It is true some elements are too heavy to have been created by the Sun's fusion process. These heavier elements would have been created ...


1

Just to add, cause I don't see it in the answers above. Continents are no heavier than oceans. As far as the Earth is concerned, they weigh about the same and they drift according to the flow of the mantle underneath. Like marshmallows in cocoa, sometimes they will drift and touch (and by touch, I mean, crash into each other and form Himalaya sized ...


1

It sounds like Ingersoll was referring to Cowling's Theorem -- that flow in a planet's core that is purely symmetric around the planet's rotation axis (that would give a magnetic dipole field with no tilt) cannot produce a self-sustaining dynamo. So a magnetic field that is purely symmetric around the rotation axis, as looks to be the case for Saturn, ...


1

"Tilt" is a consequence of a convecting metal inner core....not a "necessity". In the earth's case, that tilt has, over time, wandered from 0 to 180 degrees, sometimes with some temporal regularity, other times completely randomly. The science writer likely poorly paraphrased Professor Ingersoll's curiosity regarding the existence of a molten metal core deep ...


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