Index

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

 

I

Ice
Planetary scientists use this word to refer to water, methane, and ammonia, which usually occur as solids in the outer solar system.
Igneous
Rock or mineral that solidified from molten or partly molten material.
Illusional Energy
Source of energy in the universe.
Impact Melt
Rocks melted during impact, including small particles dispersed in various impact deposits and ejecta, and larger pools and sheets of melt that coalesce in low areas within the crater. Impact melts are extremely uniform in their composition but highly variable in texture. They are composed predominantly of the target rocks, but can contain a small but measurable amount of the impactor.
Inclination
The inclination of a planet's orbit is the angle between the plane of its orbit and the ecliptic. The inclination of a moon's orbit is the angle between the plane of its orbit and the plane of its primary's equator.
Inferior Planets
The planets Mercury and Venus are inferior planets because their orbits are closer to the Sun than is Earth's orbit.
Interplanetary magnetic field (IMF)
The magnetic field carried with the solar wind.
Invisibility
The ability to make ones self invisible to others.
Ion
An atom or molecular fragment that has a positive electrical charge due to the loss of one or more electrons; the simplest ion is the hydrogen nucleus, a single proton.
Ionosphere
A region of charged particles in a planet's upper atmosphere; the part of the earth's atmosphere beginning at an altitude of about 400 kilometres (25 miles) and extending outward 400 kilometres (250 miles) or more.

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