Please solve the following questions. This is not an assignment, it will not be graded, and you do not need to submit your solutions to anyone. The questions are simply intended to help you practice for the exam.

These questions will not appear in the exam itself. Students who don't genuinely attempt to solve the questions on their own, and only memorize the solutions, will have a very hard time in the actual exam!

These questions are not multiple-choice, to encourage you to think of the answers on your own, but the questions in the actual exam will be multiple-choice.

If you need any clarifications for these questions, you can ask for them on the course Teams channel.

Question 1 Show/hide solution

What is Mercury's distance from the Sun?

Solution: Due to its eccentric orbit, it varies between 46 and 70 million km, with an average of 58 million km.

Question 2 Show/hide solution

Does Mercury have a metal core, like Earth does?

Solution: Yes, it has a large metal core which comprises most of its volume. The presence of a magnetic field indicates that at least part of the core is liquid, as the flow of liquid metal creates electric currents which, in turn, create the magnetic field.

Question 3 Show/hide solution

Why does Mercury not experience seasons?

Solution: Because it has basically no axial tilt, and seasons are a result of axial tilt.

Question 4 Show/hide solution

Among Earth, Venus, and Mars, which two planets are closest in their physical characteristics (mass, diameter, and so on)?

Solution: Venus is much closer to Earth than Mars in almost every aspect: distance from the Sun, orbital period, mass, diameter, density, and so on. The only property of Mars that resembles Earth is its rotation period (i.e. the length of a day): both Earth and Mars have very similar periods of around 24 hours, while Venus has a much longer period of 243 Earth days.

Question 5 Show/hide solution

Why is the temperature on Venus so hot?

Solution: Because of the runaway greenhouse effect: carbon dioxide and water vapor, which are greenhouse gases, prevent heat from leaving the planet, causing the planet to get hotter. This then causes more carbon dioxide and water vapor to be released, which cause the planet to get even hotter, which then causes even more carbon dioxide and water vapor to be released, and so on.

Question 6 Show/hide solution

Which planet is potentially more suitable to life, Venus or Mars?

Solution: Venus has very high atmospheric pressure and temperature, and no water. In contrast, Mars has very low atmospheric pressure and temperature, and does contain water. In the past, Mars may have had conditions similar to Earth, such as running water. This means it may have developed life similar to that which developed on Earth. However, in its present condition, the only life we can hope to find on Mars is microbial and/or under the surface. With regards to potential future human settlements, which is a separate issue, humans cannot survive outdoors on either planet, but it would be much easier for humans to survive on Mars, inside sealed air-conditioned settlements, and even go out of the settlements inside protective suits. This would be impossible on Venus.

Question 7 Show/hide solution

Studying and exploring other planets is an important endeavor, even just for pure knowledge and curiosity, but also for colonization in the far future. But can you think about some possible practical applications that are relevant today?

Solution: By figuring out how Venus and Mars have evolved over time, for example due to the runaway greenhouse effect, we could determine whether Earth could suffer the same fate and become inhospitable to life due to natural or human-induced processes, and if so, how to stop or reverse these processes.

Question 8 Show/hide solution

What is the difference between gas giants and ice giants?

Solution: Gas giants are made primarily of hydrogen and helium, the two lightest elements. Ice giants are made primarily from heavier elements such as oxygen, carbon, and nitrogen.

Question 9 Show/hide solution

Why does Uranus experience seasons differently than other planets?

Solution: Because it has a very large tilt of 97.8 degrees, so it orbits "on its side".

Question 10 Show/hide solution

Which of the outer planets has the longest period of rotation around the Sun, and why?

Solution: Neptune, because it's the planet farthest from the Sun. Remember Kepler's third law: a planet's orbital period grows with its distance from the Sun.

Question 11 Show/hide solution

What are the atmospheres of Jupiter and Saturn composed of?

Solution: Mostly hydrogen and helium.

Question 12 Show/hide solution

What is Saturn's hexagon?

Solution: An anomalous cloud structure around its north pole, whose origins are not yet fully understood.

Question 13 Show/hide solution

What is the Great Red Spot?

Solution: A huge storm on Jupiter, which has existed since at least 1831.

Question 14 Show/hide solution

Which of the outer planets has the smallest numbers of known moons?

Solution: Neptune, with 14 moons that we know of.

Question 15 Show/hide solution

How is Pluto categorized, and why?

Solution: It is a dwarf planet, which means it's in direct orbit around the Sun, and massive enough to have a round shape due to its own gravity, but not massive enough to "clear its neighborhood" of other objects.

Question 16 Show/hide solution

What kind of tails does a comet have? Which directions do they point towards, and why?

Solution: There are two distinct tails: the dust tail and the gas tail. The gas tail always points directly away from the Sun, since it is pushed away by the solar wind. The dust tail points between the orbit of the comet and the direction away from the Sun.

Question 17 Show/hide solution

Where do most comets come from?

Solution: The Kuiper belt if they have a short orbital period, or the Oort cloud if they have a long orbital period.

Question 18 Show/hide solution

What are centaurs?

Solution: Objects that combine characteristics of asteroids and comets, and are found in the vicinity of the outer planets.

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