Meteor Impacts – Comets, Meteoroids and Effects

Geoscience Processes – Meteor Impacts

Introduction:

People studied the stars before the invention of telescopes. When they observed the sky at night, they found out that bright lights in the sky changed their position according to other lights. In those days, astronomers called these objects planets. The name planet comes from the Greek word ‘wanderer.’ A planet is a huge body that revolves around a star.

A moon is an object that revolves around a planet. Planets and moons are parts of a solar system. The solar system is made up of our star, the Sun, and everything gravitationally bound to it, including the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; dwarf planets like Pluto; dozens of moons; and millions of asteroids, comets, and meteoroids.

The other objects in the solar system are comets, meteors, meteoroids, and meteorites.

Comet:

Comets are small bodies of balls of rock, ice, and cosmic dust that revolve around the Sun. Halley’s Comet is very famous, and it passes by Earth every 76 years. It passed by Earth in 1986 and will come back in 2061.

Structure of Comets:

The comet consists of a core or nucleus, coma, and tail. The core (Nucleus) comprises rock, metals, and ice. A coma is present around the core (nucleus). It is a round cloud that consists of gas and dust. Coma can extend very far, maybe 1 million km from the nucleus. The nucleus and coma form the head of the comet. The tail is a very interesting part of the comet. Comets come from the outside borders of the solar system.

The Kuiper Belt:

There are small objects beyond the orbit of Neptune. These objects, along with comets, form a ring of icy bodies called the Kuiper belt, which is located just outside Neptune’s orbit. The dwarf planets such as Pluto and Eris are situated in the Kuiper belt.

Meteoroids

• These are small, rocky, or metallic objects that move around the Sun in both the regions (inner and outer regions) of the solar system. The craters present on the Moon were created by the collision of meteoroids. According to scientists, many meteoroids are pieces of matter that got detached from the passing by comets. Large meteoroids may be formed as a result of a collision between the asteroids.

Meteor

• When a meteoroid enters the Earth’s atmosphere, friction between the object and the air molecules creates heat. That heat heats the surface of a meteoroid and as a result of this friction and heat, meteoroids burn in the atmosphere. So, when a meteoroid burns up in Earth’s atmosphere, it produces a streak of bright light called a meteor. Meteors are also called shooting stars. When large numbers of small meteoroids enter the Earth’s atmosphere in a very short time, a meteor shower takes place.

Meteorite

• When many meteoroids enter Earth’s surface, some of them do not burn up completely because of their huge size. So, these meteoroids fall to Earth’s surface and are called meteorites. Many meteorites are small, but large meteorites sometimes hit the Earth’s surface with great force, and these impacts cause craters that can be seen in many places on Earth.
• Meteorites are of three types – stony, iron, and stony-iron. The composition of stony meteorites is the same as the composition of rocks present on Earth. Some stony meteorites consist of carbon compounds. Iron meteorites have a peculiar metallic appearance. Stony iron meteorite consists of iron and stone. But these types of meteorites are very rare.

Meteorite Impact

When a large object collides with the Earth’s surface, the rock at the impact site is deformed, and some of it is ejected into the atmosphere, eventually falling back to the surface. This creates an impact crater, which is a bowl-shaped depression with a raised rim. The size of the impact crater is determined by factors such as the size and velocity of the impacting object, as well as the angle at which it strikes the Earth’s surface.

A meteorite impact occurs when a rocky, metallic (usually iron), or icy body in orbit around the Sun passes through the atmosphere and collides with the Earth’s surface. Meteors, on the other hand, are similar objects that are so small that they vaporize or burn up in the atmosphere and do not collide with the Earth’s surface.

Larger impacts leave craters, and the largest impacts change the atmosphere, hydrosphere, and biosphere on a global scale.

Meteorites provide important information to astronomers and geologists about the composition, age, and history of the early solar system.

Most meteorites are small, about the size of a pebble, and have little impact on the Earth’s system.

Large meteorite impacts(effects) are very rare, but an impact 66 million years ago in what is now Mexico’s Yucatan Peninsula is thought to have wiped out many plant and animal species, including all dinosaurs except the ancestors of living birds.

Meteorite Flux

The total mass of extraterrestrial objects that strike the Earth is referred to as meteorite flux. This is currently between 107 and 109 kg per year. Many of these particles are dust-sized objects known as micrometeorites. The frequency with which meteorites of various sizes strike the Earth varies with their size, as shown in the graph below.

Every day, tons of micrometeorites strike the Earth. Because of their small size, they usually do not burn up when they enter the Earth’s atmosphere but rather settle slowly to the surface. Every 30 seconds, meteorites with diameters of about 1 mm strike the Earth. The friction of passage through the Earth’s atmosphere generates enough heat to melt or vaporize the objects, resulting in so-called shooting stars.

Meteorite Impacts and Mass Extinction

The impact of a space object larger than about 1 km in size would be felt across the entire Earth’s surface. Smaller objects would almost certainly destroy the ecosystem in their path, similar to the effects of a volcanic eruption, but larger impacts could have a global impact on life on Earth. We will first consider the potential effects of an impact and then discuss how previous impacts may have resulted in mass extinctions of species on Earth.

Regional and Global Effects

A meteorite (larger than 1 km in size) or a comet. Calculations and scaled experiments can still be performed to estimate the effects. Here is a summary of the general consensus.

1. Earthquake: The impact of a large object on the Earth would cause a massive earthquake – up to Richter Magnitude 13 – and numerous large magnitude aftershocks.
2. Large amounts of dust released into the atmosphere would block incoming solar radiation. It could take months for the dust to settle back to the surface. Meanwhile, the Earth would be in perpetual darkness, and temperatures would plummet across the globe, creating global winter-like conditions. A comparable effect has been proposed for the aftermath of a nuclear war (termed a nuclear winter). Solar radiation blockage would also reduce the ability of photosynthetic organisms, such as plants, to photosynthesize. Because photosynthetic organisms are at the bottom of the food chain, this would have a significant impact on all ecosystems.
3. Widespread wildfires would be ignited by radiation from the fireball as it passed through the atmosphere. The smoke from these fires would further block solar radiation, increasing the cooling effect and interfering with photosynthesis.
4. If the impact occurred in the oceans, the sudden evaporation of the seawater would produce a large steam cloud. This water vapor and CO2 would linger in the atmosphere long after the dust had settled. Both of these gases are greenhouse gases, meaning they scatter solar radiation and cause warming. As a result, after the initial global cooling, the atmosphere would experience global warming for many years following the impact.
5. A massive tsunami would be generated if the impact occurred in the oceans. The leading edge of a 10-kilometer-diameter object would strike the seafloor of deep ocean basins before the object’s top reached sea level. The tsunami generated by such an impact is estimated to be 1 to 3 km high. These have the potential to flood the interiors of continents.
6. Landslides caused by massive earthquakes caused by the impact could change the landscape at the impact site and in surrounding areas.
7. Due to the impact’s shock, large amounts of nitrogen oxides would be produced by combining nitrogen and oxygen in the atmosphere. These nitrogen oxides would react with water in the atmosphere to form nitric acid, which would fall back to the surface as acid rain, acidifying surface waters.
8. A meteorite impact could cause the extinction of many organisms, altering the evolutionary history of life on Earth, for example, by paving the way for the emergence of large-bodied mammals by eradicating large-bodied dinosaurs.
9. Massive impact events early in Earth’s history, some caused by collisions with small planets:

This resulted in the formation of the Moon.

Changed the spin, tilt, and orbit of the Earth.

As the Earth formed, it brought water with it.