Mercury: The Scorched Planet

What major challenge makes it difficult to send a spacecraft directly into orbit around Mercury?

• Mercury has a very thick atmosphere that slows spacecraft down.

• A spacecraft arriving directly would be moving too fast and would need a prohibitive amount of fuel to slow down.

• Mercury's strong magnetic field prevents spacecraft from entering orbit.
  

What surprising chemical discovery did MESSENGER find on Mercury's surface?

• The surface is covered in liquid water.

• Mercury's rocks are made entirely of ice.

• Mercury's surface contains volatile elements in higher concentrations than expected so close to the Sun.

Which idea is one proposed explanation for why Mercury has such a large metal core and little rock on its surface?

• Mercury was once much farther from the Sun and later was pushed inward after a collision that stripped much of its crust.

• Mercury formed exactly where it is now and never moved.

• Mercury captured several small moons that melted into a metal core.