The following sentences form a paragraph. The last sentence of the paragraph is given. The rest are numbered as P, Q, R, S, T, and U. These parts are not given in their proper order. Arrange them in the correct order to make the paragraph meaningful and then answer the questions given below.

P. Determining the speed of rotation of solid planets, like the earth and Mars, is pretty straightforward.

Q. Saturn has still presented greater challenges to observation as different parts of its hot ball of hydrogen and helium rotate at different speeds.

R. Such planets lack measurable solid surfaces and are covered by thick layers of clouds; so direct observation is not possible.

S. Another challenge being that its rotation axis and magnetic pole are aligned.

T. It is measured by a method which measures the time it takes for a feature on the surface to return into view.

U. But such methods cannot be used for giant gas planets like Saturn, Jupiter, etc.

7. Thus making the conventional methods of measurement redundant and truly saturnine.