Q&A Hero

Q: The Mars Rover found undisputed microfossils, proving life once existed on Mars.

Q: Mars has a weak magnetic field.

Q: Mercury has an unusually small core.

Q: The Phoenix lander on Mars failed to confirm the presence of water ice under the surface.

Q: The giant Borealis basin around the Martian north pole may have formed due to an impact with an asteroid twice the size of Ceres.

Q: The low surface gravity helps Martian volcanoes grow to great heights.

Q: Winds on Mars give rise to planet-wide dust storms.

Q: The seasonal polar caps on Mars, which grow and shrink over the year, are primarily carbon dioxide.

Q: Because of its axial tilt and more elliptical orbit, Mars' polar caps change size even more than the Earth's do.

Q: There is new evidence that water has flowed as mud on Mars in recent times.

Q: Mars appears red in color because of refraction of light by its atmosphere, much like the color of the totally eclipsed Moon.

Q: The Moon's far side is more ancient and heavily cratered; on Mars, the same is true of its southern hemisphere.

Q: The polar caps and dust storms of Mars can be seen with Earth-based telescopes.

Q: Mars has larger volcanoes than Earth's Hawaii.

Q: The surface of Mars is surprisingly smooth and featureless.

Q: No evidence of impact craters has been found on Venus.

Q: The surface temperature of Venus is 730K, even hotter than Mercury.

Q: We now know of polar caps on Mercury, the Moon, Earth, and Mars.

Q: The scarps on Mercury are extremely similar to the cratered lunar highlands in appearance.

Q: Mercury has the widest variation in surface temperatures between night and day of any planet in the solar system.

Q: Venus' surface temperature cools off at night, much like Mercury's does.

Q: Atmospheric pressure on Mars is roughly half that of Earth's at sea level.

Q: Compared to Earth, Venus spins very rapidly on its axis.

Q: Although it has no liquid water, Mercury has a tidal bulge.

Q: Mercury's rotation and revolution are an example of a 3:2 resonance.

Q: Venus can appear as a crescent through the telescope.

Q: The density of Mars is very similar to that of the other terrestrial planets.

Q: Mercury, Venus, and Earth have similar densities.

Q: Venus' rotation period is longer than its period of revolution around the Sun.

Q: Water is one of the most common substances in the universe, and vital to us on Earth. What happened to it on Mars?

Q: Why isn't there water on Venus?

Q: What is the most abundant gas in the atmospheres of Mars and Venus? Explain why it is not as abundant in Earth's atmosphere.

Q: Contrast the atmosphere of Venus with its clouds.

Q: The vast flood deposits prove Mars once had much running water. What happened to it?

Q: Relate Mercury's scarps to the differentiation process.

Q: What, other than its existence, is unusual about the magnetic field of Mercury?

Q: Why was the discovery of a substantial magnetic field around Mercury a surprise? How was it detected?

Q: Our Moon and Mars both show very different hemispheres. Compare them and explain why this occurred in each case.

Q: Mars is often called a "midway world," similar in some respects to Earth, and in others to our Moon. Explain.

Q: On our Moon, Mercury, Earth, and Mars, there are a variety of meteor craters in terms of size. Yet all those found on Venus are over 5 kilometers across. Explain.

Q: How are surfaces of Mercury and the Moon similar? Different? Why?

Q: Mars and Mercury are similar in size, and Mercury is even denser. Why then is it Mars that has more atmosphere?

Q: Why do we know much more about the surface of Mars than that of Venus?

Q: Contrast the compositions and heights of the clouds of Earth and Venus.

Q: If Venus' clouds block much of the sunlight before it reaches the surface, why is the planet so hot?

Q: On rare occasions, Mercury and Venus can transit the Sun, crossing directly between us and our Sun. If you were watching the event closely, such as on June 5, 2012, you might note a "tear-drop" effect as Venus came on and left the solar disk, very different from the disk of Mercury. Explain.

Q: Which terrestrial planets lack seasons? Why?

Q: How and why would the noon Sun appear different to an observer on Mercury compared to one on Earth?

Q: When are Mercury and Venus easiest to observe from Earth? Why? How much of then can we see at that time?

Q: While surface conditions differ greatly, name three ways that Venus and Earth are indeed "sister planets."

Q: Will Mars ever appear to the unaided eye as large as the Moon at closest approach? Explain.

Q: What is the significance of large percentage of oxygen in Earth's atmosphere?

Q: If its density suggests its core is similar to ours, why does Venus lack a magnetic field?

Q: In what way is Mercury's core unusual?

Q: Other than its atmosphere, name two properties of Venus that are unique among the terrestrial planets.

Q: How is the Mars Rover mission different from the Global Surveyor mapping mission?

Q: Where is most of the water on Mars believed to be?

Q: Describe the primary difference between the northern and southern hemispheres on Mars.

Q: What are coronae?

Q: Why were the Russian Venera spacecraft so important to our understanding of Venus?

Q: Why do our best radar maps of Venus come from the Magellan space probe?

Q: Why is the atmospheric pressure at the surface of Venus so much higher than Earth's?

Q: Describe the relation between Mercury's spin and orbit.

Q: How does the rotation of Venus' clouds compare to the rotation of its surface?

Q: If Mars' atmosphere is mostly carbon dioxide, why isn't it as hot as Venus?

Q: What is unusual about the rotational (spin) and orbital periods of Venus?

Q: Why is Venus' rotation unusual?

Q: What is the primary effect the carbon dioxide in Venus' atmosphere has on the planet?

Q: The great barometric changes accompany the sublimation of carbon dioxide in the Martian spring and summer, creating planet-wide ________.

Q: While ________ gas is the main atmospheric component of both Mars and Venus, its density means it plays a far larger role in heating Venus.

Q: The greatest rift valley system yet found is ________ on Mars.

Q: The ALH84001,meteorite, discovered in Antarctica, came from ________, and suggests it may once have had life.

Q: Carbon dioxide dominates the atmospheres of Venus and Mars, but on Earth most of it lies underground as ________.

Q: The planet ________ has the least variation in temperatures on the surface between day and night.

Q: Mercury's core is unusually ________, which may help explain its magnetic field.

Q: Directly opposite the Tharsis uplift and volcanoes on Mars lies the deep ________, perhaps suggesting impact cause and volcanic effect.

Q: The largest volcano in the solar system, ________, is found on Mars.

Q: Of all the planets, only ________ has surface features easily seen from Earth with ground-based telescopes.

Q: Why is the impact theory now preferred as an explanation for the Moon's origin?

Q: Relate our magnetic field to the aurorae.