Interesting Facts about Asteroids

NASA's spacecraft called Galileo was the 1^st one to capture close-up images of an asteroid called Gaspra in 1991. This celestial body appears very similar to the moons of Mars called Phobos and Deimos.

Asteroids are celestial objects consisting mainly of rocks and metals. They are majorly concentrated in the region known as the asteroid belt, which lies between the orbits of Mars and Jupiter. They can be as big as Ceres, which is close to 1,000 kilometers in diameter, or can be just a few feet in diameter.

Whatever their size, asteroids are neither big enough to be called planets, nor are they as small as comets. The Kuiper Belt Objects and the Oort Cloud Belt are also two other regions in space that show the presence of these bodies. Asteroids that have possibly been converted to moons of a planet are Phobos and Deimos, the two satellites of Mars.

A few more might have been captured by Jupiter's gravity and converted to its moons. The ones that consist of a diameter less than 10 meters are known as meteoroids. The average temperature of the surface of an asteroid is around -100°F (about -73°C).

Ancient theories supported the conclusion that they are formed due to the explosion of a planet between Mars and Jupiter.

'Accretion of mass' is also a principle that has been supported regarding their origin. In this theory, these bodies are said to have formed after collision of two or more objects (for example, dwarf planets, comets, meteorites, etc.), thereby, resulting in accretion of matter, further resulting into large bodies.

According to present-day astronomical research, these celestial objects are said to be remnants of debris that have been left behind since the Big Bang (the most popular theory regarding formation of the Universe). This debris could not form a planet in our solar system because of the effect of Jupiter's gravitational pull.

Several other debates talk about the impact of a small planet on Mars, which ejected massive amounts of rock fragments in varying sizes and shapes, thus, forming part of the asteroid belt.

On January 1, 1801, Giuseppe Piazzi discovered the first asteroid, which he initially thought to be a comet. He named it Ceres after the Sicilian Goddess of grain, and it is the largest asteroid to have been discovered till present.

It has now been designated as a dwarf planet, and roughly accounts for about ¼th of the total mass of all known asteroids. Area-wise, this object is about the size of the state of Texas.

On the contrary, '1991 BA' is the smallest asteroid, which measures about 6 meters (20 ft.) in length.

Soon, other massive ones like Pallas, Juno, and Vesta were discovered.

By the end of the 19th century, several hundreds of asteroids were found in the same belt.

Till now, at least one of them has been observed and discovered every year, since 1847.

These bodies are present mainly in the outer portion of the belt and are included under the 'C class' of asteroids.

The ones showing medium levels of carbon content are included under the 'D class', and are mainly composed of frozen carbon dioxide and water. They are called 'Jupiter Trojans'.

The ones categorized under 'S class' show the presence of iron and magnesium silicates, and comprise about 17% of the total number of these objects. They are characterized by a distinct reddish brown-colored surface.

The 'V class' asteroids are composed of materials forming igneous rocks like basalts. They also show the presence of pyroxene mineral in high amount.

The rarest type of asteroids are included under the 'M class'. These are characterized by an iron core, with traces of nickel metal. Due to their proximity to the Sun during the time of their formation, these objects developed a metallic core that resulted from a differentiation process between the metallic and non-metallic contents.

With the help of software programs, a computer can trace the path of the asteroid by making assumptions of where it will be positioned at particular times.

The observations are matched along with the predicted positions, thereby, resulting in the representation of their elliptical orbits.

The path of an asteroid varies in its distance regarding its revolutions around the Sun, mainly because of the effect of Jupiter's and Sun's gravity. The perigee (closest distance)
and apogee (farthest distance) points of its deviation are calculated, and these are known as Kirkwood gaps.

After its position has been confirmed, the particular asteroid is named, firstly by giving it a number, and then by attaching the number with an alphabet serial code. It is officially named only when a thorough study has been done.

Hidalgo is an asteroid that has the largest orbit that stretches till about 9.7 AU (astronomical units). Contrary to this, Icarus has the smallest orbit having a maximum limit of 2 AU.

The ones that enter the atmosphere are called meteors, while the ones that undergo burning and appear as shooting stars are called meteorites.

According to the Giant Impact Theory, the Moon was created when Theia, an asteroid of the size of Mars, collided with the Earth in the early days of the solar system. However, some consider Theia to be more of a planetoid than an asteroid.

One of the largest craters caused by an asteroid hit is the Chicxulub crater in Mexico, which is 180 km in diameter. The asteroid that formed this crater had a diameter of 10 km. This collision is supposed to be responsible for the extinction of a large number of flora and fauna including dinosaurs.

However, the evidence of the largest asteroid hit is the Vredefort crater in South Africa, which is 300 km in diameter. According to fossil records, there have been at least three mass extinctions on our planet due to asteroid impacts.

While some planetoids are capable of sending thermal waves that can incinerate most flora and fauna within a few hundred kilometers, other larger ones can create huge craters, causing magma to cover areas as big as continents.

The worst effect is the blocking out of sunlight for months together due to the formation of dust clouds and soot in the upper atmosphere. This would hamper the plants' ability to prepare food through the process of photosynthesis, and the food chain would be disrupted.

Such bodies are classified as:

• The Amors: They cross the orbit of Mars, but do not go out of the Earth's orbit.
• The Apollos: They cross the Earth's orbit, but have an orbital period of greater than one year.
• The Atens: Their path crosses the Earth's orbit, but have an orbital period of less than one year.

Asteroids are currently being monitored for their probability of collision with our planet. Studies have predicted that they may hit the Earth on February 1, 2019, and March 16, 2880. The probability of the second collision is as high as 1 in 300.

A number of projects in the field of astronomy, like Spacewatch, Near-Earth Asteroid Tracking, Catalina Sky Survey, etc., are being carried out to detect any threat of such catastrophes.

In 2001, the NEAR (Near Earth Asteroid Rendezvous) spacecraft landed on the asteroid Eros, it being the 1^st spacecraft to have landed on an asteroid. In the last decade, NASA's Dawn was launched, which started exploring the asteroid Vesta. This spacecraft is expected to reach the largest asteroid Ceres till 2015.

Gold, lead, uranium, platinum, etc., are some of the important minerals that are present in asteroids, according to several spectral studies and related analysis. It has been estimated that the entire amount of mineral resources extracted from these objects would be sufficient for about 40% of the Earth's population.

Asteroids can be said to be a very crucial option for exploring mineral resources to replace the shortage faced by the ones on Earth that are exhaustible in the near future. Also, if these celestial bodies are studied in an extensive manner, they might lead us to the solution of the formation of our Universe.