In-class test 4 for ASTR 201: The Sun and its Planets

Test will be the first 15 mins of class on Nov 23 and will comprise one of the following questions.

It is the year 2020 and a new terrestrial planet has been discovered around a nearby Sun-like star. Its mass has been measured to be twice Earth's mass, and it orbits its star at the same distance as Earth orbits the Sun. A mission has been sent to explore the planet.

(1) What tectonic activity might the astronauts expect to find on this planet? Explain your reasoning.

(2) Would you expect the planet to have an atmosphere? If so, would it be made of elements like the Earth's atmosphere (mostly nitrogen plus some oxygen)? If not, what would you expect its major constituents to be? Would it be a dense atmosphere? Explain your reasoning.

(3) The next stop for the astronauts is the star Sirius, which is much brighter and hotter than our Sun. It has a planet at the same distance from Sirius as Jupiter is from the Sun. The astronomers have been unable to obtain images or a good mass estimate of this planet because of technical problems with their telescopes. Would you expect this planet to be a gas giant or a terrestrial planet? Explain your reasoning.

(4) Explain how the differences in mean density of the Earth and Moon have forced astronomers to propose that they formed in a giant impact of a Mars-sized planet with the Earth.

(5) What surface features on Mars make scientists more likely to consider the theory that Mars had primitive life many billions of years ago? Why would the life be unlikely to have survived to the present day?