A study of comets
The nucleus of Halley's Comet was unexpectedly extremely dark black — its surface, and perhaps those of most others, is apparently covered with a black crust of dust over most of the ice, and it only releases gas when holes in this crust expose ice to the sun.
In this case, the impact debris would spread throughout the Earth's atmosphere so that plant life would suffer from acid rain, partial blocking of sunlight, and from the firestorms resulting from heated impact debris raining back down upon the Earth's surface.
Orbital characteristics Astronomers classify comets based on the durations of their orbits around the sun. Recently, scientists have also discovered comets in the main asteroid belt — these main-belt comets might be a key source of water for the inner terrestrial planets. In general terms, comets are now thought to be made up of early outer solar system material that agglomerated into rather fragile matrices of jet-black, potato-shaped, icy dust-balls.
When Halley's Comet zoomed near Earth infive spacecraft flew past it and gathered unprecedented details, coming close enough to study its nucleus, which is normally concealed by the comet's coma.
Comets whose aphelia are near a major planet's orbit are called its "family".
Research on comets
However, gravitational perturbations from giant planets cause their orbits to change. When the solar wind passes through this ion coma, the bow shock appears. As the primitive, leftover building blocks of the outer solar system formation process, comets offer clues to the chemical mixture from which the giant planets formed some 4. The roughly potato-shaped, 9-mile-long 15 km comet contains equal parts ice and dust, with some 80 percent of the ice made of water and about 15 percent of it consisting of frozen carbon monoxide. By what process did this material transport occur? Indeed, we may owe our preeminence at the top of Earth's food chain to cometary collisions. This happened in to Comet Holmes. The infant bow shock is asymmetric and, relative to the distance to the nucleus, wider than fully developed bow shocks. Some comets have comas that can reach nearly 1 million miles 1. The probability of an asteroid striking the Earth and causing serious damage is very remote but the devastating consequences of such an impact suggests we should closely study different types of asteroids to understand their compositions, structures, sizes, and future trajectories. One day soon, comets may serve as watering holes for space travel and fueling stations for interplanetary spacecraft. As with asteroids, comets are both a potential threat and a potential resource for the colonization of the solar system in the twenty first century. This makes it a good target to study evolutionary change in the mantle or upper crust of the comet. Don Yeomans Why Study Comets? As soon as life could have formed on our planet, it did.
Its rotation will not take the impact crater out of the spacecraft's field of view during the encounter period.
based on 20 review