A100 -- Dan Swearingen Homework 5.
Due Tuesday, November 5 by the beginning of class
1. Explain WHY there is a distinct trend in the density and composition of the major planets.
The trend in composition of the planets is that the planets near the Sun are small and rocky while the planets further out are large, are mostly hydrogen and helium, and increasingly icy as you move further out from the Sun.
This trend is thought to have been caused by the conditions found in the early solar system. As material condensed and spiralled in towards the proto-solar nebula, there was a strong trend in temperature in the nebula. Near the object which eventually would be the Sun the temperature was very hot, thousands of degrees Kelvin. As you moved further away the temperature dropped off. Near the proto-solar nebula only materials like Silicon, Iron, and Nickel could solidify. Other materials like Hydrogen and Helium stayed in their gaseous state and were blown away from the early Sun where they would accumulate in the outer solar system and form the gas giants such as Jupiter and Saturn. Left in the inner solar system were the terrestrial planets, made of the materials found in those regions: Silicon, Iron, and Nickel.
2. How many bodies in the solar system are larger than 1000 km in diameter? Organize your list by major planet: Jupiter, Jupiter's moons, etc.
Looking at the table in the appendix of our text I listed everything with a radius greater than 500 km:
Sun
Mercury
Venus
Earth:
Moon
Mars
Jupiter:
Io
Europa
Ganymede
Callisto
Saturn:
Tethys
Dione
Rhea
Titan
Uranus:
Ariel
Umbriel
Titania
Oberon
Neptune:
Triton
Pluto:
Charon
I count 25.
Questions for Review , page 225:
17. What is the evidence that Mars once had running water on its surface?
There are three main pieces of evidence that there was once running liquid water on the surface of Mars. First there are observations of channels in the surface which share so many characteristics with similar water-made structures on Earth that we assume water must have made them on Mars too. Second, there are collapsed regions around several places on Mars which experienced localized heating like vulcanism and meteor strikes which we think are places where water ice under the soil melted and flowed.
Third: If the we can confirm the discovery that life once existed on Mars then liquid water must have existed.
18. How do astronomers explain why the Earth's atmosphere ended up with so little CO2 compared with Mars and Venus?
Life and H2O have moved almost all of the CO2 that was once in the Earth's atmosphere into the oceans and rock. Life, mostly in the form of small plankton like creatures in the oceans, stores CO2 in its bodies and then carries it to the bottom of the oceans when the creatures or plants die. Water carries CO2 out of the atmosphere and conveys it to mineral deposits and the water in the ocean stores large amounts of CO2 in solution (the oceans are slightly carbonated).
Thought Questions, page 225:
4. What role might planetesimal impacts have played in the history of the terrestrial planets?
Planetesimals, small solid bodies formed in the early solar system, had several effects on the development of the terrestrial planets. By colliding and combining they built up the mass of the terrestrial planets. Icy planetesimals which formed in the outer solar system delivered water and other compounds (possibly including Life!) which couldn't survive in the inner regions of the proto-solar nebula. Planetesimal impacts are probably the cause for Venus's "backwards" rotation and a planetesimal impact on the early Earth probably formed our moon.
Questions for Review , page E5-10:
1. What is the earliest evidence for life on Earth?
The ealiest evidence for life are fossil remains of algea and bacteria found in rocks determined to be 3.8 billion years old.
2. How old are the earliest life forms thought to be?
The answer to number 1 above covers this.
3. What features of life [on Earth] are suggestive of a common origin?
Features common to all life forms on Earth are carbon-based orgainc chemistry, use of a common molecule to convey energy (ATP), and the storage of genetic information in DNA strands.
4. What is meant by panspermia?
Panspermia is the idea that life spreads through the galaxy like a virus or bacteria, travelling on small or large particles through space, infecting any appropriate host (planet).
Questions for Thought , page E5-10:
1. (write a one to two page essay).
I graded on whether your essay was readable and logically self-consistent.
5. Use a method similar to the Drake equation to estimate the number of people getting a haircut at some given moment. That is, multiply the probabilities of each such event times the number of people in, for example, the United States. [modify as follows: how many people in Bloomington are getting a haircut ... ]
I estimate that there are about 60,000 people in Bloomington. People get their hair cut about once a month. When they get their hair cut they mostly have it done sometime between 9:00 am and 6:00 pm (9 hours).
So the probability of someone getting a haircut today is 1/30.
The probability of their getting a haircut this hour is 1/9.
60,000 people x 1/30 x 1/9 = (about) 200 people getting a haircut right now.
So, at 75% booking, there is probably good employment for about 300 hairdressers in Bloomington. Examining the phone book I counted about 130 Barber Shops and Beauty Salons.