Spectacular fireworks lit lit up the sky on July 4, 2005, as a probe crashed into a comet's surface. But the Deep Impact Mission was not about pulverising comets. It was about knowing what comets are made of. And understanding the origin of our solar system…
Four and a half billion years. That’s the approximate age of our solar system. During its formation, fragments of rock, gases and other materials were thrown around in space. With time these merged to form celestial objects — planets and comets. Earlier, comets were thought to be bad omens bringing doomsday theories in their wake. Today, scientists believe comet impacts played a major role in earth’s evolution, bringing water and organic compounds to our planet. Every civilisation has been curious about comets. And this curiosity made NASA (National Aeronautics Space Administration) launch the Deep impact mission to explore Comet Tempel 1. But why study a comet and what did the mission find?
To meet a comet
In 1867, German astronomer Ernst Tempel discovered a comet, probably formed in the Kuiper Belt — a disk-shaped region beyond Neptune housing many comets. It was named Tempel 1 after him. Scientists believe comets are leftovers containing the building blocks of our solar system and they wanted to explore Tempel 1 to understand its composition. On July 4, 2005, the Deep Impact spacecraft launched a projectile, aimed to hit Tempel 1. The impact gave off a huge shaft of light, created a crater and released fine dust. The 4,500 images taken by the spacecraft show a huge cloud of powdery substance that seemed finer than beach sand — like talcum powder! This surprised everybody — the comet was made of a substance softer than snow! This suggests that the comet has been built up over a long period of time.
Another interesting find could tell us how the solar system interacts with comets. NASA's satellite report shows how water evaporates on Tempel 1 — an important clue to understand how solar wind stripped water from planets like Mars. Comets become visible because ice evaporates from their surface, with each close passage around the sun. Scientists will learn about this evaporation process happening quickly now (over a few weeks) as a result of human intervention on Tempel 1. The impact crater may also tell us whether comets trap ice or exhaust it for their survival.
Tale of a comet
Comets are remnants of the material in the coldest part of our solar system. About half the mass of comets consists of ices of volatile substances like water, carbon dioxide and carbon monoxide. The rest is rocklike dust bound together by the ice. Comets spend most of their lives frozen in the Oort Cloud (a spherical shell 10,000 times apart from sun than earth) and the Kuiper Belt. Their forays into the inner solar system are brief. Astronomers believe that the original material that formed comets, has remained undisturbed inside comets. Exploring frozen comets may open a window to the past. And that is what Deep Impact has set out to do — unlock the secrets about the origin of the solar system…