AU- one astronomical unit is the average distance from the Earth to the Sun. 1AU= 149,597,870 kilometers, or 92,960,116 miles.

chromatography- this process involves a sample being vapourised and injected onto the head of the chromatographic column. The sample is transported through the column by the flow of inert, gaseous mobile phase. The column itself contains a liquid stationary phase which is adsorbed onto the surface of an inert solid.

coma-a dense cloud of water, dust, carbon dioxide, and other neutral gasas sublimed off of an active comet's nucleus.

comet-small, irregular celestial bodies that race around in elliptical orbits that bring them close to the sun and back to deep space.

dust tail-smole-sixe dust particles driven off the nucleus by sunlight in the opposite direction of the sun.

heliocentric-

hydrogen envelope-huge but very spare cloud of neutral hydrogen.

ion tail-cloud of ions that stream from the nucleus of the comet. nucleus- fragment of primitive material preserved since the beginning of the solar system that is the center of the comet which is relatively solid and stable while being composed of ice and gas with a small amount of dust and other solids.

perihelion- the point in a planet's orbit where it is closest to the sun.

planetesimals- basic building blocks that form planets.

solar nebula- rotating cloud of vapor.

solar wind-a flow of gas and energetic charged particles, mostly protons and electrons, that stream from the Sun at velocities of about 350 kilometers (217 miles) per second.

sublime-sublimation occurs when a substance changes directly from a solid to a gas without becoming a liquid.

supervisory control- a robot is assigned a task by a human, but has enough intelligence for it to carry out those instructions with no further assistance.

volatiles-compounds with low melting temperatures, such as hydrogen, helium, water, ammonia, carbon dioxide, and methane.