MARK’S HYPOTHESIS THAT HE WASN’T OBTAINING CRYSTALS BECAUSE BACTER...

10. Mark’s hypothesis that he wasn’t obtaining crystals because bacteria were feeding on his samples:f. was probably correct.g. was probably incorrect.h.was not formed in accordance with the scientific method.j. could not be tested.

Passage III

IS PLUTO A PLANET?Scientist 1Based on perturbations in Neptune’s orbit, the search for a ninth planet was conducted, and Plutowas discovered in 1930. Pluto orbits the Sun just as the other eight planets do, and it has a moon,Charon, and a stable orbit. Based on its distance from the Sun, Pluto should be grouped with theplanets known as gas giants. In addition, Pluto, like the planet Mercury, has little or no atmosphere.Pluto is definitely not a comet because it does not have a tail like a comet when it is near the Sun.Pluto is also not an asteroid, although its density is closer to an asteroid than to any of the otherplanets. Pluto is a planet because it has been classified as one for more than sixty years since its dis-covery.Scientist 2Pluto should no longer be classified as a planet based on new evidence that has come to light inthe last few years. When Pluto was first discovered, nothing was known about its orbit or its com-position. Pluto has an orbit that is not in the same plane as the other planets (i.e., it is tilted) andits orbit is more eccentric, or elongated than any other planet’s orbit. Pluto orbits the Sun in theouter solar system, and so should be similar in size and composition to the gas giants, but it is not.Pluto lacks rings that all other gas giants possess. Also, Pluto’s moon is larger than any other moonrelative to its parent planet. In recent years, new objects have been found which belong to theKuiper Belt, a region of small solid icy bodies that orbit the Sun beyond the orbit of Neptune andPluto. A large object called Quaoar has recently been discovered which has a density nearly iden-tical to Pluto, Charon, and Triton. Based on these facts, I conclude that Pluto is a Kuiper Belt object.