Impact Craters

comparative Essay
1196 words
1196 words

Impact Craters

An impact crater (impact basin or sometimes crater) is a circular depression on a surface, usually referring to a planet, moon, asteroid, or other celestial body, caused by a collision of a smaller body (meteorite) with the surface. In the center of craters on Earth a crater lake often accumulates, and a central island or peak (caused by rebounding crustal rock after the impact) is usually a prominent feature in the lake.

Ancient craters whose relief has disappeared leaving only a "ghost" of a crater are known as palimpsests. Although it might be assumed that a major impact on the Earth would leave behind absolutely unmistakable evidence, in fact the gradual processes that change the surface of the Earth tend to cover the effects of impacts. Fortunately, scientists have discovered some untouched craters around the universe.

Impact craters found on different planetary regions

The Moon

The surface of the moon is scarred with millions of impact craters. There is no atmosphere on the moon to help protect it from bombardment from potential impactors (most objects from space burn up in the Earth's atmosphere). Also, there is no erosion (wind or water) and little geologic activity to wear away these craters, so they remain unchanged until another new impact changes it. These craters range in size up to many hundreds of kilometers, but the most enormous craters have been flooded by lava, and only parts of the outline are visible. The total area of the moon is 37 930 000 square kilometers.

One of these craters found, is the Alfrancus C. It has a maximum diameter of 10 km and a maximum radius of 5km. It has an estimated depth of 1.2km.

Alfrancus C

Planet Mercury

Mercury is in many ways similar to the Moon: its surface is heavily cratered and very old; it has no plate tectonics. On the other hand, Mercury is much denser than the Moon (5.43 gm/cm3 vs 3.34). Mercury is the second densest major body in the solar system, after Earth. Actually Earth's density is due in part to gravitational compression; if not for this, Mercury would be denser than Earth. Mercury has a total area of 75 000 000 square kilometers and is the closest planet to the sun in the solor system. This indicates that Mercury's dense iron core is relatively larger than Earth's, probably comprising the majority of the planet. Mercury therefore has only a relatively thin silicate mantle and crust.

In this essay, the author

  • Compares mercury to the moon in terms of its cratered surface and its dense iron core, which is larger than earth's.
  • Describes the caloris basin as an impact crater on mercury. it is a maximum of 1350km in diameter and 9km deep.
  • Explains that the moon has the largest dimensions of craters, whereas the earth has smallest.
  • Explains that an impact crater is a circular depression on earth's surface caused by the collision of smaller bodies with the surface.
  • Explains that the surface of the moon is scarred with millions of impact craters. there is no atmosphere to help protect it from potential impactors.
  • Explains that mars, like all terrestrial planets, has been modified by impact cratering processes. wind, water, weather, volcanic activity, and tectonic forces combine to erase evidence of the many impacts.
  • Explains that earth was formed around 4.57 billion (4.57109) years ago and experienced the early periods where the solar system was "clearing out" rocks. aorounga is an impact crater in chad, africa.
  • Explains that if comets and asteroids strike all regions of a planetary body at approximately the same rate, every region should have crater density.
  • Explains that craters come in different shapes and dimensions. earth's largest is vredefort, while the moon has the largest impact basin aitken.
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