Assignment #12

Assignment #12 (1) Pluto (5 pts.) Why don’t astronomers consider Pluto to be a major planet anymore? Write a paragraph giving a careful and thorough scientific explanation. There are several reasons for astronomers do not consider Pluto to be a major planet anymore. First, Pluto is too small to be included, it is much smaller than other major planets. Second, even Pluto is as dense and rocky as some other major planet in solar system, the planets that Pluto is closest to are gaseous, which indicate that Pluto formed other place in the galaxy rather than solar system, it was captured or caught by the Sun’s gravity. Third, the orbit of Pluto is 17-degree angle compared to its plane, while other major planets have relatively flat orbital plane. Last, among the moons of Pluto, one moon is about half the size of Pluto, which makes astronomers consider these two as a binary system rather than planet and satellite system in solar system. (2) The Atmosphere of Mars (6 pts.) Today, the planet Mars is about 1.5 AU from the Sun, while Venus is 0.72 AU from the Sun. Suppose that instead, 4.6 billion years ago, Mars had formed at 0.72 AU from the Sun, but was in every other way unchanged. How would you expect the atmosphere of Mars to be today in terms of quantity and chemical composition? (Obviously it would be warmer.) Please choose one of the three options below, and then write a thorough and detailed defense of your response. a) The atmosphere of Mars would be similar to how the atmosphere of Mars is today. b) The atmosphere of Mars would be similar to how the atmosphere of Venus is today. c) The atmosphere of Mars would be very different from either how Mars or Venus are today.

I would expect the atmosphere of Mars would be very different from either how Mars or Venus is today (Option c). If the Mars had formed at 0.72 AU from the Sun, it would lose its atmosphere quickly because its weaker gravity can’t maintain the gases. I suppose the Mars would be a warmer planet which lacks atmosphere. (3) Cloud Bands (5 pts.) Astronomers discover a planet orbiting around another star. The star is very much like our Sun, and the planet is almost a twin to Jupiter. The planet has the same mass as Jupiter, is the same distance from its star as Jupiter is from our Sun (5.2 AU), has the same orbital period (12 years), is the same temperature, and has the same density and chemical composition as Jupiter. However, when we take a close up picture of the planet, we find that its clouds are not lined up in East/West bands like Jupiter. Instead the clouds appear to randomly swirl around. Propose a hypothesis to explain why this planet's clouds would not be organized into East/West bands like we see on Jupiter. The reason that the clouds in Jupiter are lined up in East/ West bands is resulted from the direction of wind on Jupiter. The direction the winds flow on Jupiter is in East/West direction, which push the clouds to move in the same direction. So, if the winds on this planet move in different directions, this can cause the clouds to appear to randomly swirl around. (4) Meteorite Ages (5 pts.) When meteorites fall to the earth, we can sometimes measure the ages by studying the amounts of different radioactive elements that they contain, in pieces called "calcium-aluminum-rich-inclusions". The oldest known meteorites are slightly less than 5 billion years old. Suppose that in the future, we use radiometric dating on a meteorite and find that it is 7 billion years old. To explain this unusually large age, someone proposes: "Perhaps this meteorite is from another galaxy." Evaluate this proposal. Does this hypothesis make sense? Write a few sentences explaining why or why not. If not, propose a similar but more reasonable hypothesis. This hypothesis doesn’t make sense. Since our galaxy is 13.6 billion years old. This meteorite may come from the same galaxy but different planetary

120*10 6 /80=1500000cm=15000m=15km (1 pt.) (e) Fossils tell us that life first existed on land about 400 milion years ago - those are the fish that flopped about and learned to breath air - put that date on the timeline 400*10 6 /80=5*10 6 cm=5*10 4 m=50km (1 pt.) (f) The earliest life is thought to have appeared on Earth about the time of the end of the period of heavy bombardment of the planets (when the cratering slowed down). This makes sense, doesn't it, that the slime and creepy-crawlies would have a hard time surviving until the aerial bombing ceased - that was about 3.8 BILLION years ago. Where does this event go? 3.8*10 9 /80=47500000cm=475000m=475km (1 pt.) (g) Calculate where we should put the formation of the Earth,4.6 billion years ago. 4.6*10 9 /80=57500000cm=575000m=575km (1 pt.) (h) Finally, calculate the location on our timeline of the big bang, the formation of our universe 13.7 billion years ago 13.7*10 9 /80=171250000cm=1712500m=1712.5km (6) The Mass of the Asteroid Belt (5 pts.) (a) The mass of the asteroids is found mostly in the larger asteroids, so to estimate the total mass we need to consider only the larger objects. Suppose the three largest asteroids—Ceres (1000 km in diameter), Pallas (500 km in diameter), and Vesta (500 km in diameter)—account for half the total mass. Assume that each of these three asteroids is a sphere with a density of 3 g/cm 3 and calculate their total mass. Then, multiply your result by 2 to obtain an estimate for the mass of the total asteroid belt. Report your final result in kilograms. Please show/explain your work. No credit will be granted for responses which don't show each step in your calculations.

Since V=4/3*pi*r 3 , diameter=2radius, Radius of Ceres=500km, Radius of Pallas=250km, Radius of Vesta=250km, Volume of Ceres=4/3*pi*(500) 3 =5.23*10 8 km 3 =5.23*10 17 m 3 Volume of Pallas=4/3*pi*(250) 3 =6.54*10 7 km 3 =6.54*10 16 m 3 Volume of Vesta=4/3*pi*(250) 3 =6.54*10 7 km 3 =6.54*10 16 m 3 Total volume of three asteroids=6.538*10 17 m 3 Since  =m/v,  =3 g/cm 3 =3000kg/m 3 Mass of three asteroids=3000*6.538*10 17 =1.96*10 21 kg Mass of total asteroid belt=2*1.96*10 21 kg=3.92*10 21 kg (3 pts.) (b) Use your estimate of the mass of the asteroid belt to calculate: The total mass of the asteroid belt is what percent of the mass of our Moon? Please show/explain your work. No credit will be granted for responses which do not indicate how you used your mass estimate to calculate this percentage. Mass of our moon=7.35*10 22 kg Mass of total asteroid belt=2*1.96*10 21 kg=3.92*10 21 kg Mass of asteroid belt/Mass of moon=3.92*10 21 kg/7.35*10 22 kg=5.3%