What is the main visual difference between the lunar highlands ...

[ahriuashd]

What is the main visual difference between the lunar highlands and the lunar maria? What are the implications of this observation?
 
  What will be an ideal response?

Question 2

What is a planetary nebula?
 
  A) The bipolar jets ejected by a T Tauri variable
  B) A planet surrounded by a glowing shell of gas
  C) The disc of gas and dust surrounding a young star that will soon form a solar system
  D) The ejected envelope, often bipolar, of a red giant surrounding a stellar core remnant
  E) A type of young, medium mass star

[kardosa007]

Answer to Question 1

The lunar highlands are very heavily cratered and the lunar maria are generally smooth. (More specifically, the maria contain only 3 percent as many craters per unit area as the highlands.) The difference in the amount of craters shows that the maria formed after the highlands, at the end of the heavy bombardment phase of the solar system. Radiometric dating of rocks from the highlands and maria shows that the heavy bombardment phase lasted no longer than a few hundred million years.

Answer to Question 2

D

[ahriuashd]

Thanks for the timely response, appreciate it

[Dinolord]

Gracias!