WITH loose material brought home by various space probes, it will be established once and for all that the Solar System is after all some 4.5 billion years old. Until then the ‘extras’ will keep the key stashed away from our prying eyes.

Although nothing matches the major players of the Solar System in grace, poise and their size, the ‘extras’ like asteroids, meteorites, meteors and the so called shooting stars, still play a vital role in the mechanics of the System. Above all, they would help reveal the age of the System.

Whatever we know about the age either comes from terrestrial or lunar rocks. This is not to deny the importance of the ‘extras’, one day soon when science (actually technology) has advanced enough, we can put these objects to confirm our estimation of the Solar System, because we believe that these objects are intrinsic — not having changed at all since their birth. Or not having gone through metamorphosis like other bodies of the System. There is absolutely no erosion on their surface, and virtually no volcanic action deep inside, ever to have caused any change on their surface features.

To me it never seems simple that as against the far bigger bodies all around them, little things like meteors, asteroids and meteorites, even comets, should be allowed to form and not swallowed by the giants in the process that took all those billions of years. What are these ‘extras’ in the first place? Let us take a close look at them.

Asteroids

THESE are little bodies, rocky and cold, measuring from a little grain of dust to the largest being bigger than our dear province of Sindh, such as Ceres, which is 500km in diameter.

Although there are billions of asteroids orbiting the sun in their own respective orbits, most of them are no bigger than grains of sand. Some 1,000 are 100km in diameter. Together they weigh no more than a small moon, about 1/4 of our Moon in size. In the course of their orbits they bump into one another, rubbing off some of their matter, some of which travels as loose material scattered between asteroids. These bits are barely bigger than grains of sand. It appears that all of these asteroids were once clumped together before gravitational tug of the nearby planets (Mars and Jupiter) broke them into a million pieces over the passage of time, which is many billion years. Asteroids are thus constrained to lie in orbit between these two planets.

Once in a few million years, one of them is either pulled or pushed by the gravitational force of one or the other planet. It is then forced to plunge into these planets or their moons. Sometimes in the course of their travels, they ram into each other with the same result. Let us not forget that many of these are round, but most of them are not. Remember the moons of Mars?

Meteors

THESE are tiny bits of rock, or debris that roam the skies aimlessly. Occasionally, one enters the atmosphere of Earth some 80km above the surface. As it is pulled towards the surface it burns up with friction caused by the high speed of its fall and we see a brightly lit streak of light across the sky. Meteors are tiny pieces of matter but they add to the Earth’s weight by an ominous 10,000 tonnes every year.

Remember that whether it is meteors, asteroids or whatever else, they end up falling on all and every planet, even the Moon with the same action and result.

Those that burn up as they enter Earth’s atmosphere are called meteors and those that survive the plunge are called meteorites as they leave their footprints upon the Earth’s soil, later studied by scientists to determine what they are and their composition.

The study of the intact meteorites provides scientists with a clue about the birth of the Solar System and many other riddles are answered in the process. It is very surprising that those that survive are usually metallic in composition. Another remarkable thing is the question: how they came to be there; whether they formed together with the Solar System or separately, and under what circumstances?

In my considered (and humble) opinion, they were one body some billion years in the past. Then that body broke apart into several pieces, which broke into many more, and many more again until there was nothing left of the original, except a billion pieces big and small due to the gravitational tug of nearby planets and moons, as we saw earlier.

Though the gravity that they exert on the nearby bodies is negligible, they still can make it up with incredible force that results if one of them ever happens to strike, let us assume planet Earth. A boulder a few kilometres across can cause enough devastation to wipe out an entire city.

Comets

ENOUGH has been said in the recent past about comets. The question that still haunts us astronomers is: where did those billions of comets come from? There must be a tangible explanation for their mysterious birth and their presence. In my reckoning, comets existed at the time the Solar System did just as other bodies did. The difference is that their place was somewhere in the middle of the system, and not several billion miles away, as it is at the present time. The Sun itself was much bigger, bloated and wilder in the earlier epochs, so that it drove away the tiny pebbles, thanks to the powerful solar wind. Eventually those little pebbles came to rest in the outpost of the System, still held by the Sun’s massive gravity.

That’s how I think the comets came into being. It is for you to reach your own conclusion. Many astronomical theories are based on pure conjecture, but sound basic knowledge may lead you to draw better conclusions than me.