1.   A NASA mission to the asteroids Mathilde and Eros.
3.  The natural satellites orbiting around planets.
5.  The abbreviation for electromagnetic radiation with wavelengths that are 
      just a little shorter than visual light.
7.  A spacecraft launched on September 25, 1997 to measure the composition 
     of the solar wind.
8.  The smallest particle into which an element can be broken.
9.  A spacecraft, launched in 1995, which is orbiting above the Earth's north 
     and south poles.
10. The planet closest to our Sun.
11. The abbreviation for the speed of light.
12. Dark regions on the Sun's surface, where it is not as hot as the surrounding 
      areas.

1.  The very high density central part of an atom consisting of protons and 
     neutrons.
2.  The abbreviation for the amount of energy needed to move an electron 
     through a one volt electrical potential.
4.  A period of time seen by the number of sunspots on the Sun and lasting 
     about 11 years.  (2 words)
6.  An oscillatory motion of something in nature.
7.  A unit of electrical current equivalent to about 6 X 1018 electrons per second.
10.  The fourth planet from the Sun.