Question 1

The Martian moon Phobos orbits near the equatorial plane of Mars in just over 7.5 hours in the same direction as the planet rotation. How then would one see Phobos move across the Martian sky from the surface of the planet?

Accepted Answer

Phobos orbits Mars faster than Mars rotates, completing an orbit in just over 7.5 hours. Since Mars rotates in the same direction as Phobos's orbit but more slowly, Phobos appears to move across the sky from west to east, opposite the direction of most celestial objects as seen from Mars. Because its orbital period is shorter than a Martian day (about 24.6 hours), Phobos can be seen rising and setting multiple times within a single Martian day.

Question 2

The exploratory life-sciences experiments aboard the Viking spacecraft landers found evidence of

Accepted Answer

The Viking landers' experiments found highly reactive chemical processes in the Martian soil but did not provide conclusive evidence of life or biological processes.

Question 3

What evidence have some scientists claimed for ancient life on Mars (although the hypothesis has been strongly disputed by many other scientists)?

Accepted Answer

The evidence claimed by some scientists for ancient life on Mars includes microscopic features in a Martian meteorite (ALH84001) that are similar to biologically generated features on Earth. This claim has been controversial and is not widely accepted as conclusive evidence of past life on Mars.

Question 4

The shapes and sizes of the two moons of Mars are

Accepted Answer

The two moons of Mars, Phobos and Deimos, are indeed irregular in shape and very small, with diameters of only several tens of kilometers.

Question 5

The unstable chemicals dissolved in the Martian regolith suggest that the amount of ultraviolet radiation reaching the surface of Mars is much greater than the amount reaching the surface of Earth. The Martian atmosphere lacks which constituent in sufficient quantities to absorb incoming ultraviolet radiation?

Accepted Answer

Ozone is crucial for absorbing ultraviolet radiation in the Earth's atmosphere. Mars lacks a significant ozone layer, which allows more ultraviolet radiation to reach its surface compared to Earth.

Question 6

Which of these craters are the youngest?

Accepted Answer

The youngest craters among the options given would be the oldest craters on Venus. This is because Venus has a relatively young surface geologically speaking, due to its thick atmosphere and volcanic activity that resurfaces the planet more frequently than the other bodies mentioned. This means even the oldest craters on Venus are younger than the oldest craters on Mercury, the Moon, and Mars.

Question 7

Phobos orbits Mars in a prograde orbit with a period less than the rotational period of Mars itself. What consequence follows from this?

Accepted Answer

Phobos orbits Mars faster than Mars rotates on its axis, causing it to rise in the west and set in the east, opposite to the usual direction for celestial bodies as seen from Earth.

Question 8

According to modern dynamo theory, the production of a planetwide magnetic field around a terrestrial-type planet appears to require

Accepted Answer

Modern dynamo theory suggests that a planetwide magnetic field is generated by the movement of a conductive fluid, typically in a molten metallic core, combined with the planet's rapid rotation. This movement and rotation create a dynamo effect that produces the magnetic field. A permanently magnetized solid core (option B) does not align with the dynamo theory's mechanism for generating a magnetic field.

Question 9

Where did some scientists claim that they have found direct evidence for life, either contemporary or ancient, beyond Earth that has since been disproven?

Accepted Answer

The claim of finding direct evidence for life in meteorites composed of ancient Martian rock refers to the famous case of the ALH84001 meteorite. In 1996, a team of scientists announced that they had discovered potential signs of ancient microbial life in this meteorite, which originated from Mars. This claim was based on the presence of microscopic structures resembling bacteria, along with chemical signatures and mineral formations that could be biogenic in origin. However, the interpretation of these findings as evidence of life has been highly controversial and widely disputed within the scientific community. Over time, alternative non-biological explanations for the features observed in ALH84001 have gained support, and the claim of direct evidence for life has not been substantiated.

Question 10

The moons of Mars are

Accepted Answer

The moons of Mars, Phobos and Deimos, are irregularly shaped, cratered, and grooved, indicating a non-spherical appearance and a surface marked by impacts and possibly tidal forces.

Question 11

A global magnetic field generated from inside the planet is found around which terrestrial planet or planets?

Accepted Answer

Mercury and Earth are the only terrestrial planets in our solar system that have a global magnetic field generated from their interiors. Venus and Mars do not have a global magnetic field; Venus has a very weak one induced by the solar wind, and Mars only has remnant magnetism in certain areas of its crust.

Question 12

On which of these planets have experiments been carried out to search for life-forms or evidence of life?

Accepted Answer

Mars has been the focus of several missions and experiments, such as the Viking landers, which searched for signs of life or conditions suitable for life.

Question 13

An atmosphere containing a significant amount of oxygen is found around which terrestrial planet or planets?

Accepted Answer

Earth is the only terrestrial planet in our solar system with a significant amount of oxygen in its atmosphere, primarily due to the presence of life processes, particularly photosynthesis, which produces oxygen.

Question 14

The Moon raises tidal bulges on Earth and as a consequence is being pulled gradually away from Earth. Phobos raises tidal bulges on Mars and as a consequence is being pulled gradually toward Mars. Why this difference?

Accepted Answer

Phobos orbits Mars more quickly than Mars rotates, which means the tidal bulges it creates are always slightly ahead of it in its orbit. This leads to a transfer of energy from Mars to Phobos, slowing down Mars' rotation slightly but accelerating Phobos. However, due to the dynamics of orbital mechanics, this actually causes Phobos to spiral inward towards Mars, unlike the Moon which is spiraling outward away from Earth because it orbits slower than the Earth rotates.

Question 15

If one characterizes the age of a surface by the age of the oldest feature that has been dated there, then the ages of these surfaces are, from youngest to oldest,

Accepted Answer

Venus has a relatively young surface due to its extensive volcanic activity, which resurfaces the planet. Mars and the Moon have older surfaces, with the Moon having the oldest visible surface features due to its lack of geological activity compared to Mars and Venus. Earth's surface is constantly being recycled through plate tectonics, making it difficult to find extremely old surface features, but it is not an option paired with Venus and Mars in the correct order.

Question 16

Several aspects of Mars render it hostile to life on the planet. Which of these components is NOT one of these factors?

Accepted Answer

The answer of Several aspects of Mars render it hostile...

Question 17

What were the results of the life-sciences experiments aboard the Viking landers?

Accepted Answer

The Viking landers' life-sciences experiments detected strong reactions releasing oxygen, but subsequent analysis suggested these were due to nonbiological causes, such as chemical reactions with the Martian soil, rather than evidence of life.

Question 18

When were the two moons of Mars, Phobos and Deimos, discovered?

Accepted Answer

The two moons of Mars, Phobos and Deimos, were discovered in 1877 by American astronomer Asaph Hall.

Question 19

Phobos and Deimos are moons of which planet?

Accepted Answer

Phobos and Deimos are the two moons of Mars, orbiting closer to their planet than any other moons in the solar system.

Question 20

What role has methane played in the search for life on Mars?

Accepted Answer

The presence of methane on Mars suggests it is being renewed continually, possibly by living organisms, as sunlight breaks down methane within a few centuries.

Quiz 8: The Other Terrestrial Planets