When the Martian axis tilt is large, the Martian poles A) ...

[schs14]

When the Martian axis tilt is large, the Martian poles
 
  A) expand and remain permanently frozen, thinning the atmosphere
  B) contract and partially vaporize, thickening the atmosphere
  C) extend over the entire surface of the planet
  D) completely disappear

Question 2

What are gravitational waves? Have they ever been detected?
 
  What will be an ideal response?

[voltaire123]

Answer to Question 1

B

Answer to Question 2

Gravitational waves are ripples of spacetime caused by the motion of massive objects (the more massive the object, the greater the ripples). They travel at the speed of light but are so weak that they have not yet been detected. New telescopes are being built, however, to search for them. The effect of gravitational waves has been seen in the orbital decay of a very close binary neutron star system: the gravitational waves carry energy away from the binary and the two neutron stars move closer and closer together, speeding up their orbits measurably. Based on estimates of the number of binary neutron star systems, scientists expect to detect 10 or more events per year with Advanced LIGO.

[schs14]

Thank you!

[voltaire123]

Always glad to help...