Introduction to the Solar System

What we have been studying in this course is the Universe revealed to us by science
Science is a methodology, a way of thinking about the natural world and uncovering the truth about it. It uses rational thought, observation, modeling, hypothesis making and testing, logic, and honesty to attempt to make sense of what we see in the Universe.
Since Descartes, this method of truth seeking has proven to be enormously successful at figuring out how the Universe is put together and how things work.
In addition, because we develop understanding of nature, we can manipulate it to achieve control
Control over our environment and the harnessing of the predictive power of science is technology
Technology, in turn, improves out ability to explore the Universe, and to understand more about nature
The success we've had in harnessing Nature's forces has resulted in a society that is totally dependent on the continued use of technology
We live in a scientific and technological world, with economic power and success totally tied to the use and development of technology
The power of science and the technology it has spawned is awesome and taken for granted. Science moves on, uncovering truth, discovering laws, feeding our technology and our economy
Yet most of us are not quite aware of how the scientific process works
Science proceeds by an established method, modernized from the way Plato and Descartes envisioned it, and modified somewhat to fit our economic style
Today, science is carried out at Universities, Industries (large companies that have research departments or small companies that exist on government contracts), the Department of Defense, and Government Labs (like NASA)
Scientists are usually trained for 6 years or so, during which time, as graduate students, they learn the methodology from their advisors. They read most of the current scientific literature on a small number of specialized subjects, and become conversant with the observations, theories and ideas expressed in the literature
They use mathematics, computer models, telescopes, laboratory experiments to investigate how nature works, and usually use and adapt the methods taught them by their advisors
Eventually, when the scientist or student believes they have discovered something new, some new idea, observations or synthesis, they write it up in a formal paper designed to take the reader through their data and reasoning
The literature is usually in the form of specialized journals who acquire their papers through the process of peer review
Peer review is the key to scientific honesty. The writer sends their manuscript to the editor of the journal they wish to be published in.
The editor then sends the paper out to 2 or 3 experts in the field, who review it critically for mistakes or inconsistencies
Usually, the writer has to respond to the reviewers' comments, either refuting the criticisms, or doing more writing or scientific work to satisfy the questions that come up
The process is repeated, until the writer, reviewer and editor are satisfied that the paper contains scientific truth, and is consistent with everything else that has been done in the field
The paper is then published, and becomes part of our vast storehouse of knowledge, the scientific databank of our society
An example of what is scientific and what isn't -- I reviewed a paper from someone that the editor had labeled a 'crackpot'. Any one can submit a paper, regardless of degree or institution
But sometimes, the editor receives a paper that totally lacks an understanding of the basic natural laws (like a perpetual motion machine), or makes up fantastic theories completely unsupported by the previous work done in the field. These kinds of writings are filtered out by the scientific 'quality assurance program', peer review
Funding to scientist works the same way
If you are a University professor, you have a potentially permanent job, although you have to go through the tenure process
Some (not very many) scientists are civil servants, employed by NASA ore the USGS
Most are funded year by year on 'soft money'. That is they don't really have a job -- they write a proposal to a government agency like NASA or the NSF, and my be funded with salary for 2-3 years.
At the end of this time, they can propose something else, and it may get funded
Currently, only a small fraction of proposals get funded
The funding process involves peer review, in a manner similar to the one for getting papers published

The total amount of money spent on science and technology by the US Government is 70 billion dollars, about 2% of the total US budget
1/2 of this goes to the Department of Defense, mostly for weapons development
Medical Sciences get 17%
NASA gets 12% (mostly hardware)
DOE gets 9% (Rocky flats, energy projects)
NSF gets 3% (mostly direct funding of scientific research)
NASA's budget is about $14 billion a year, about 12% of the total US budget devoted to science and technology
Of that, just over half is the Space Shuttle ($6 billion) and Space Station ($2 billion)
These are largely engineering projects, with very little science
They mostly support the aerospace industries and the military industrial complex
About $1 billion a year is actually spent on space science -- astronomy, all the space missions, laboratory work
About $300 million is used to directly support research in planetary astronomy research, excluding the hardware for mission
All the knowledge we have acquired and discussed in this course comes from that
All the science we have talked about, the images, the interpretations, the data, the theories, have come from a group of about 1000 scientists

The Earth is a tiny, rocky world orbiting an average star along with other small rock worlds and several huge gas giant planets
Our ordinary star orbits inside the Milky Way Galaxy along with 100 billion other ordinary (and some not so ordinary) stars
Our galaxy, the Milky Way, is an average spiral galaxy, one of 100 billion in the solar system
Our solar system formed from the gravitational contraction of a huge cloud of gas and dust in the Milky Way
The planets formed by the condensation of metal and silicate dust, ice and frozen gas grains. These accreted into planetesimals, which accreted into planets
The composition of the planets is determined by the condensation sequence. Close in to the newly forming Sun, materials that are solid at high temperatures condensed (metals). Further out, where it was cooler, silicate (rocks) condensed. Further out still, water vapor condensed out as ice. And even further out, gases froze out.
Moons formed around the gas giants in much the same way that the planets formed around the Sun. They were subjected to the heat of the forming planet, and thus evolved from a condensation sequence
The solar system consists of small rocky, metallic planets within about 1.5 AU of the Sun. It has gas giants from 5 to 30 AU. Asteroids populate the solar system between the rocky (terrestrial) planets and the gas giant planets. Beyond the planets exist the 100 billion or so icy and carbonaceous objects called comets
Comets formed inside Neptune's orbit were thrown out into a spherical shell around the solar system know as the Oort cloud
Comets formed outside Neptune's orbit stayed there, in a place we call the Kuiper belt
Comets are made of ice, carbonaceous material, and frozen gases, and have a large organic molecule content
Comets have the organic precursors of amino acids and sugars
Pluto, it's moon Charon, and Neptune's moon Triton may all be giant Kuiper belt objects
Comets and carbonaceous objects are the oldest, least altered objects in the solar system
Tides are the friction in planetary motion. They can heat up moons close to giant planets and cause differentiation. They can also cause geological activity
Geological activity is the expression of heat being lost by a planet. It consists of volcanism, where hot liquid erupts onto the surface, and of tectonism, where solid crust buckles or breaks, causing mountains or plate tectonics.
Geological activity on the surfaces of solar system worlds is common. On the terrestrial planets, volcanism is the erupting of hot molten rock. On icy moons, it is the eruption of ice slush and dirt. On the furthest out moons, volcanism is the eruption of frozen gases onto the surface
The Earth is divided into the crust, mantle and iron core. The core is made of the heaviest material, iron and nickel. The mantle is made of dense rocks. the crust is the lower density scum that floats on top
The process by which the Earth developed a core and crust is called differentiation
Shield volcanoes form by the rising of hot plumes of material rising up from the mantle and impinging on the bottom of the lithosphere
Plate tectonic is the process of one tectonic plate sliding under another, and recycling rocks and carbon into the mantle
Enormous volcanoes exist on the all terrestrial planets (except Mercury), but there is no evidence of plate tectonics
Mars has evidence of a huge canyon system that developed from a crack in the crust, due to the uplifting of a huge volcanic province
There was once flowing water on the surface of Mars, but not today
There is evidence for impact craters on all the solid bodies of the solar system. Most of the craters we see were due to the impact of left-over planetesimals from the beginning of the solar system
The geological age of a surface can be estimated from the number of impact craters. Younger surfaces have few craters, because they have been wiped out by erosion, tectonism, or volcanism. Older surfaces have many impact craters, and have been relatively untouched by these processes
The Earth, Venus, and Io have young surfaces, because they have recently been or are undergoing reworking. The Moon and Mercury have very old surfaces, with almost no processes reworking the surface
The Gas Giants have no solid surface -- just deep thick atmospheres of H2 and He below methane or ammonia clouds
The Earth started with a steam and CO2 atmosphere. As the Earth cooled, the atmosphere condensed and rained out, creating oceans. The CO2 that was in the atmosphere dissolved in the oceans, and reacted with rock on the bottom. This thinned out the CO2 atmosphere, and now most of it exists in huge limestone deposits
The Moon formed from a giant impact hitting the Earth just after it was formed
Planets that orbit outside Earth's orbit show retrograde motion in the sky. That is, Mars, Jupiter, Saturn
Objects in the sky move from E to W, and rise 4 minutes earlier every day due to the Earth's orbit around the Sun. The constellations change with the seasons due to this
The summer solstice is when the Sun gets the highest in the sky and the day is longest
The winter solstice is when the Sun is the lowest it ever gets at noon, and the day is the shortest
During the equinoxes (fall and spring) the day is exactly 12 hours long, every where on the Earth
The Moon goes through phases because it orbits the Earth, and from our perspective on Earth, we see the Moon illuminated at different angles over the month
The greenhouse effect is due to the fact that the Earth's atmosphere is transparent to sunlight, but opaque to heat energy. Heat energy emitted by the surface gets absorbed in the atmosphere, heating it up
The greenhouse effect exists on every planet or moon with an atmosphere
Mars is about half the size of the Earth. The Moon is about half the size of Mars. Venus is the same size as the Earth
Mars and Venus both have CO2-N2 atmospheres.
The Earth's atmosphere is 3/4 N2, 1/4 O2, and only a tiny amount of CO2
CO2 is kept in balance in the Earth's atmosphere with the carbonate-silicate cycle. Rain water reacts with rocks to dissolve carbonate in water. The water finds its way to the ocean, where it is precipitated out to the ocean floor as a carbonate mineral. The minerals subduct with the plates and are released again into the atmosphere through volcanism
There is life on the Earth that does not depend on sunlight
We looked for life on Mars, but couldn't find any
Titan is the big moon of Saturn, where we thing organic chemistry is going on similar to the kinds of chemistry that happened on the Earth before life began
There has been life on Earth for nearly all of its history
The spacecraft exploration of the planets has showed us what our neighboring worlds look like The most important thing about understanding the solar system is the perspective it gives us.
The technology we have developed to explore these worlds can also help us achieve a mature understanding of our own planet, and provide the understanding it takes to live on it in a sustainable way
All this understanding, all this exploration and revelation has taken place in only the last generation. The space age began only 40 years ago, when the planets were just fuzzy dots in our telescopes. In only one generation, we have sent our robots out and done what 1000s of generations only dreamed of: explored the other worlds of our Solar System. In one generation, we have totally altered the human perspective, of our place in the cosmos.

Grading will be done with the following formula:
Observing 10%
HW 40%
Exam 1 15%
Exam 2 15%
Final 20%

Get all homework in by 5 today

Formula with a 100 point scale

(obs)+(40/70)*(HW1+HW2+HW3+HW4+HW5+HW5+HW7)+(15/100)*Exam1+
(15/100)*Exam2+(20/100)*Final

Galilean Moons
Io
Europa
Ganymede
Callisto
shepherd moons
ice volcanism
ice tectonism
grooved terrain
Earth impact hazard
size-frequency plot
Bode's Law
carbonaceous
hydrocarbons
methane-nitrogen clouds
ethane-acetylene haze
methane cycle on Titan
orbital eccentricity
Voyager
troposphere
tropopause
stratosphere
stratopause
Titan's oceans
tidal forces
synchronous rotation
The Cassini mission
carbonate-silicate cycle
frozen gases
greenhouse effect
condensation sequence
panspermia
Jupiter
Saturn
Uranus
Neptune
Pluto
The Kuiper belt
The Oort cloud
Triton
Titan
Charon
The Centaurs
Newton's Laws
sulfur volcanism
Percival Lowell
CCD
Mission to Planet Earth
silicate dust
astronomical unit (AU)
asteroid
comet
Jovian planets
Gas giants
terrestrial planets
Impact theory for the formation of Charon

VIDEO: MISSION TO PLANET EARTH, SPACE AGE SERIES (Second half)

7/2/96