Short period comets come from the Oort Cloud outside the solar system. Their continual supply from the Oort Cloud is proof that the solar system is billions of years old. Life from elsewhere in the universe has been discovered on comets.
The Facts Are .....
The problem for evolution is that if short period comets only last about 10,000 years, and the solar system is 5 billion years old, then there should not be any of these comets left in existence. As short-period comets have been visible this century (eg Halley's comet), the solar system must be considerably younger than the date assigned to it by evolutionary theory. [based on logic]
The belief in a 5 billion year old solar system has led to a hypothesis that these comets must be resupplied from outside the solar system - an example of a preconceived idea determining scientific belief. A vast shell of 100 billion comets, called the 'Oort Cloud' is theorized to exist at the outer edge of the solar system. Passing stars are supposed to disturb the cloud enough to knock a comet into an inner orbit. This is a theory that is not based on any observed facts.
The facts about the Oort cloud are:- (1) It has never been observed, and should be regarded as an evolutionary prediction; (2) The calculated motions of comets do not match well with any predictions based on the Oort Cloud; and (3) Cometary evidence does not support the existence of an Oort cloud.
Some researchers believe that if the Oort theory is true, then some comets from our solar system should have escaped. Likewise, we should have seen about six comets over the past 150 years from other star systems. 
As the Oort Cloud has not been discovered yet, new theories are rising to explain the existence of short-life comets. The latest theory is that "Halley's comet comes from a second much closer belt of millions of comets just outside the solar system left over as debris and junk when the outer planets formed 5 billion years ago". This theory is spoken of in a factual manner, yet is not based on fact. 
A theory put forward for the origins of short-period comets states that they are belched out of volcanoes, most probably on Jupiter. But, (1) the theory is not supported by observation; (2) there is no planetary mechanism that would impart the force needed to expel the comets; (3) the physical makeup of comets does not match this origin; and (4) the comet would need to be travelling at over 700 Km/sec to escape a large planet, a speed which would cause it to vaporize in the process. Harold S.
Slusher, "Age of the Cosmos: ICR technical Monograph #9", 
The evidence of life on comets is based on infra-red analysis of Haley's Comet which indicated that organic matter was pouring out of its head and tail. A study of the data, however, suggests that these organic molecules are not the kind associated with living organisms. 
- Astrophysics and Space Science, Vol. 31, 1974
- Astrophysics and Space Science, Vol. 31, 1974 p:385-401
- Science Frontiers, May-June, 1990 p:1; Sky & Telescope, Vol. 79, 1990 p:254
- The Advertiser (Adelaide), May 14, 1988 p:20
- Institute for Creation Research: San Diego, 1980 p:49
- The Sydney Morning Herald, April 3, 1986 p:2