The basalt on the Moon Figure 4a is very similar in composition to the crust under the oceans of Earth or to the lavas erupted by many terrestrial volcanoes.
The youngest of the lunar impact basins is Mare Orientale, shown in Figure 4b. Figure 4: Rock from a Lunar Mare and Mare Orientale a In this sample of basalt from the mare surface, you can see the holes left by gas bubbles, which are characteristic of rock formed from lava. All lunar rocks are chemically distinct from terrestrial rocks, a fact that has allowed scientists to identify a few lunar samples among the thousands of meteorites that reach Earth.
Its outer ring is about kilometers in diameter, roughly the distance between New York City and Detroit, Michigan. It is located on the edge of the Moon as seen from Earth. What we do know is that the major mare volcanism, which involved the release of lava from hundreds of kilometers below the surface, ended about 3. The primary forces altering the surface come from the outside, not the interior.
The surface is fine and powdery. I can pick it up loosely with my toe. But I can see the footprints of my boots and the treads in the fine sandy particles. The surface of the Moon is buried under a fine-grained soil of tiny, shattered rock fragments. The upper layers of the surface are porous, consisting of loosely packed dust into which their boots sank several centimeters Figure 5. Figure 5. This lunar dust, like so much else on the Moon, is the product of impacts. Each cratering event, large or small, breaks up the rock of the lunar surface and scatters the fragments.
Ultimately, billions of years of impacts have reduced much of the surface layer to particles about the size of dust or sand. In the absence of any air, the lunar surface experiences much greater temperature extremes than the surface of Earth, even though Earth is virtually the same distance from the Sun.
Maria or Highlands: Which is Older? The maria that fill the lowlands must have formed later, thus the maria are younger than the highlands. The Moon, of course, has no atmosphere, so we see craters of all sizes. What are the differences between mare and highlands? The highlands are heavily cratered and mountainous. From the two AMIE images it is possible to see how highlands present a very irregular topography and many craters, while the mare area is comparatively flat and shows a much smaller number of craters.
The endogenic crater Feature 1 has is superposed on top of the arcuate rille Feature 2 , indicating that it is younger than the rille. It also morphs it requiring the Rille to be there first to be morphed.
The Maria-Highland border Feature 3 is the oldest feature. Outside the core is the largest region of the Moon, called the mantle. The lunar mantle extends up to a distance of only 50 km below the surface of the Moon.
Scientists believe that the mantle of the Moon is largely composed of the minerals olivine, orthopyroxene and clinopyroxene. Craters are the most common surface features on many solid planets and moons—Mercury and our Moon are covered with craters. This portion of the Moon is covered by numerous circular holes.
Further, different parts of the surface of the Moon exhibit different amounts of cratering and therefore are of different ages: the maria are younger than the highlands, because they have fewer craters. The oldest surfaces in the Solar System are characterized by maximal cratering density. The smooth and dark maria cover 17 percent of the surface of the moon.
Almost all of them are visible from Earth. Currently, it is known that these vast dark plains are formed by basalts from volcanic eruptions, which are a widespread volcanic rock on Earth. However, the lunar basalts are completely devoid of water and contain few volatile elements. Rille, any of various valleys or trenches on the surface of the Moon. The maria basins were formed beginning about 3. The count is over 3, in animation The bad news is How did the moon form?
Good question All prior models had to account for the fact that the moon has a lower density than the earth, has very little iron and contained less volatile gasses than earth rocks. Here were some major now obsolete theories: Fission Theory - The earth was initially rotating so fast that a blob of mantle material was flung out into space This idea seems ridiculous but was actually taught in my grade school.
This would explain why the moon had such a low density and accounts for the Pacific Ocean basin. Modern computers allow all kinds of possible simulations and at no time does it offer this solution.
Capture Theory - To account for the differences in density, simply have the moon form somewhere else in the solar system where the planetesimals have a lower density. Then it has to migrate from there and get captured by the earth's gravity as it moves past.
Astronomers have a problem getting the moon dislodged from its initial position and have bigger problems getting it captured by the earth. In computer simulations, the passing moon either crashes into the earth or gets whip lashed to a remote location.
Double Planet Theory - The moon and earth formed together, from the same debris, and at the same time. Why, then, would they not have the same density? No adequate theory held up. It suggests that during the very early process of accretion of planetesimals, two large worlds were forming about 1 AU from the sun. Eventually one object about the size of Mars and known as Theia collided at a glancing angle with the other which was about the size of Earth.
The collision put large amounts of debris in orbit around the earth, which quickly coalesced, This theory explains the similarities between earth and moon rocks.
In addition, the energy from the impact depleted any volatile gasses and the ejected material would have been mostly low density, mantle type rocks, This hypothesis is consistent with the idea that collisions were plentiful in the early ages of the solar system. Maybe the best part is that this scenario is played out in computers, and it actually works.
So far, it is the best hypothesis used to explain why we have our moon. If this was the case, the earth once had a system of rings like Saturn long, long ago. It still remains a mystery why "our" side of the moon looks so much different from the back side. We know the crust is much thicker on the back side. Some theories rely on tidal forces in the early formation to produce this asymmetry. Others have proposed an early impact near the south pole blasted huge amounts of debris towards the back side.
Still other ideas involve a collision between two moons which formed around the earth an extension of the collision-ejection model.
Maybe you have an idea????
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