Astronomy Chapter 7

Discuss the roles that ammonia, hydrogen sulfide, and methane play in the appearances of the jovian planets.

Ammonia- influence Jupiter's cloud colors, makes up Jupiter's clouds Hydrogen Sulfide- Also produce clouds on Jupiter, Saturn Methane- presence in upper atmosphere make Uranus and Neptune appear blue-green

Uranus and Neptune are often called twin worlds. How do their axial tilts differ?

Uranus Tilt: 98 degrees. Its strange tilt produces extreme seasonal variations, especially at the poles. So at the poles, 42 years of daylight followed by 42 days of night. Neptune Tilt: 29 degrees, seasons last 40 years

In what ways are the magnetic fields of Uranus and Neptune unusual?

Uranus and Neptune have very irregular magnetic fields - with magnetic "equators" which do not even circle the planet. Both have fairly strong magnetic fields. Magnetic fields are offset from the planets' centers and are not aligned with planets' rotation axes.

Do you think that sending humans to Mars in the near future is a reasonable goal? Why or why not?

I think that it is reasonable. With new evolutions in materials technology, suits might be a more viable option for surface exploration. One of the biggest barriers in sending humans to Mars is the surface composition, and since technology is always evolving, it will eventually happen.

Contrast the differential rotations of the four jovian planets. Explain.

Jupiter- small; higher latitudes take 6 minutes longer than equatorial Saturn- small; 26 minute difference, slower at the poles Uranus- greater; 2 hour difference, poles rotate more rapidly Neptune-greater; 6 hour difference, poles rotate more rapidly

Name two ways the magnetic fields of Uranus and Neptune defy the normal behavior of planetary magnetic fields.

Magnetic fields are offset from the planets' centers and are not aligned with planets' rotation axes.

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

Mars has more atmosphere than Mercury because if you are closer to the Sun, the atmosphere is hotter and the molecules are moving faster and so can reach escape velocity. This is why Mercury has no atmosphere, but Mars has a thin atmosphere due to its moderately slow rotation rate. Further from sun, molecules cannot reach escape velocity.

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

Mars: Northern hemisphere is largely rolling volcanic plains, somewhat like lunar maria but larger. Volcanic rock and meteoric impact areas. Southern hemisphere consists of heavily cratered highlands. North surface is younger, and scientists believe that the southern hemisphere is the original crust of the planet. Scientists think that a 2000 km impact caused northern hemisphere to be lower than southern. Moon: The two hemispheres have distinctly different appearances, with the near side covered in multiple, large maria (Latin for 'seas,' since the earliest astronomers incorrectly thought that these plains were seas of lunar water). The far side has a battered, densely cratered appearance with few maria. Only 1% of the surface of the far side is covered by maria,[1] compared to 31.2% on the near side. According to research analyzed by NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, the reason for the difference is because the Moon's crust is thinner on the near side compared to the far side.[2] The dark splotches that make up the large lunar maria are lava-filled impact basins that were created by asteroid impacts about four billion years ago. Though both sides of the Moon were bombarded by similarly large impactors, the near side hemisphere crust and upper mantle was hotter than that of the far side, resulting in the larger impact craters.[3] These larger impact craters make up the Man in the Moon references from popular mythology.

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

Rocky, cratered surface. Signs of volcanic activity. Evidence of polar ice masses. Minerals and metals in surface rocks.

Contrast the rotation rates of the jovian planets with the terrestrial planets.

The jovian planets rotate (spin) more rapidly than do the terrestrials. The slowest-rotating jovian planet, Uranus, has a rotation period that's less than 18 hours long; Earth's 24-hour period is the shortest among the terrestrials (and Venus takes 243 times longer than that for one full spin!) Jupiter is so big and spinning so fast that its equator is moving about 25,000 miles per hour relative to the center of the planet: this, combined with Jupiter's primarily liquid interior, makes Jupiter noticeably oblate (flattened), with a polar diameter that's only about 90% as big as its equatorial diameter.

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

The most abundant gas in the atmospheres of Mars and Venus are carbon dioxide. In the formation of Earth's atmosphere, the carbon cycle took place and balanced the formation and condensation of carbon dioxide. Nitrogen was released by solar ultraviolet radiation and a nitrogen-rich atmosphere appeared. However, in the formation of Venus' atmosphere, carbon dioxide never left the secondary atmosphere in the same way. Venus is closer to the sun, so more water vapor means that the atmosphere is more insulated and the surface is hotter. More carbon dioxide would enter the atmosphere from the ocean and surface rocks, causing the runaway greenhouse effect.

Discuss the seasons of Uranus. How might the odd tilt of Uranus have been produced?

The seasons are very extreme because of the odd tilt (98 degrees). This means that one side of Uranus always faces the sun. The odd tilt might have been created by an impact.

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

There is no water on Venus or Mars.. solar winds, a stream of charged particles from the sun, could be responsible for stripping away the hydrogen atoms. While the solar winds don't directly strike the planet's surface, the solar winds have been stripping atmospheric gas around the planet steadily, resulting in the lack of water on both planets. The hydrogen were part of water molecules. Much of Mars' original water is now locked in a layer of permafrost. 4 billion years ago, ass the Martian climate changed, the running water began to freeze and formed the permafrost. Volcanism then heated the surface, melting the permafrost and creating outflow channels. The water was then refrozen into the permafrost.

Why did astronomers suspect an eighth planet beyond Uranus?

There were irregularities in Uranus' motion, so astronomers suspected that the gravity from another planet beyond Uranus must have been affecting it. Used Newton's law of gravitation. Used the perturbation theory. The positions of Uranus were different than expected.