Regular atoms did not show up in the universe until when? What ...

[lak]

Regular atoms did not show up in the universe until when?
 
  What will be an ideal response?

Question 2

What is the most convincing piece of evidence to suggest that Martian meteorites actually come from Mars?
 
  A) they are igneous rocks
  B) they contain trapped gases with a similar composition to the Martian atmosphere
  C) they are red in color
  D) they show evidence for having been in contact with water

[Liddy]

Answer to Question 1

A few hundred thousand years after the Big Bang, when decoupling allowed the energy to escape, and cooled off the matter until electrons could orbit protons at temperatures of less than 3000 K.

Answer to Question 2

B

[lak]

Excellent

[mohan]

Gracias!