On rare occasions, Mercury and Venus can transit the Sun, ...

[wrbasek0]

On rare occasions, Mercury and Venus can transit the Sun, crossing directly between us and our Sun.
 
  If you were watching the event closely, such as on June 5, 2012, you might note a tear-drop effect as Venus came on and left the solar disk, very different from the disk of Mercury. Explain.

Question 2

Which terrestrial planets lack seasons? Why?
 
  What will be an ideal response?

[todom5090]

Answer to Question 1

Mercury is airless, but the dense Venusian atmosphere can refract sunlight, creating the bending of light noted in the tear-drop.

Answer to Question 2

Mercury and Venus are both so close to the Sun that it probably tidally locked their equators toward it. Without an axial tilt the angle of the Sun's rays never changes so there are no seasons.

[wrbasek0]

Thanks

[todom5090]

Welcome