Ses4u Final Assessment Part 1: Impact Craters

SES4U Final Assessment Part 1: 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. One of the craters found on Mercury is the Caloris Basin.

The Caloris Basin, also called Caloris Planitia, is an impact crater on Mercury. It is a maximum of 1350km in diameter and has a large depth of 9km, one of the largest impact basins in the solar system.

Planet Mars

Mars, like all the terrestrial planets, has been modified by impact cratering processes. Craters were formed by meteorites impacting the surface of the planet. On the Earth a variety of forces combines to erase evidence of the many impacts that have occurred. Wind, water, weather, volcanic activity, and tectonic forces on Earth have eroded most craters. Many craters on Mars are still visible because of reduced amounts of geologic activity and weather. The size of Mars is much smaller in comparison to Earth's, this is because all of mars is dry and there is no oceanic areas. The total area of Mars is 1.448Ч108 km2 (55,907,000 square miles), which is 89 973 595 square kilometers.

One of the craters found on Mars is Airy crater. The Airy crater is a maximum of 40 kilometers in diameter and is located at 0.1oE 5.1oS in the Meridiani Planum region on Mars. This crater has a depth of 5.3km.

Earth

Earth (also known as The Earth), is the home to our people. As our planet was formed around 4.57 billion (4.57Ч109) years ago, it has experienced the early periods where the solar system was "clearing out" rocks. During this period the Earth was hit with serveral asteriods and meteriors. These left craters all over our planet and several craters can be found around our planet even today. Below is one of the impact craters found by scientists/archelogists. It is named Aorounga and is found in Chad, Africa. The total area of the Earth is approximately 510 million square kilometers

Aorounga is an impact crater in Chad, Africa. It is a maximum