EARTHSCI FINAL EXAM REVIEW
Discovery of Ceres
People started looking for large and small “floating” debris, and in doing so discovered that
there was a remarkable space between the planets Mars and Jupiter. According to the
mathematical relationship of planet positions in the solar system (see Titius-Bode Law), there
really should be another planet in that space
1801: discovery of the first object in that space was made by Giuseppe Piazzi, a monk but also
the director of the Palermo Observatory in Sicily. He named that asteroid Ceres which has now
been classified as a dwarf planet.
· Asteroid: a natural rocky object in space measuring 100 m to several hundred kilometres in diameter.
· Meteoroid: a natural rocky object in space measuring from a few millimetres to 100 m in diameter.
· Meteor: the visual streak of light associated with passage of a small meteoroid through Earth`s
atmosphere; the heat energy producing the light is a result of friction between the object and molecules
of gas in the atmosphere. Remember – a meteor is not the object, only the light phenomenon.
· Fireball: the light associated with a large meteoroid or asteroid as it interacts with the atmosphere.
· Meteorite: a fragment (any size) of either a meteoroid or asteroid that lands on Earth`s surface.
Please remember – it is not called a meteorite until it actually lands on surface.
Titius-Bode Law (Rule)
Mathematical sequence to explain relationships between planet orbits
How it works:
1. Take the simple mathematical series 0, 3, 6, 12, 24, etc. Note that each successive
number is double the previous one.
2. Add 4 to each of the above, getting: 4, 7, 10, 16, 28, etc.
3. Now divide each of the above numbers by 10 to get: 0.4, 0.7, 1.0, 1.6, 2.8, etc. These
are the predicted planet spacings in Astronomical Units.
Main Asteroid Belt – asteroids are found between the gap of Mars and Jupiter
Jupiter’s mass had an enormous effect on the motions of small bodies anywhere close to it
because of its gravity.
Gravitational perturbations (i.e., disruptions) caused by Jupiter`s gravity prevented any of those
objects from merging into a single planet-sized body. Gradually, over a long period, each asteroid is influenced by these forces to change its position
and swing either out ward or inward from Jupiter, leaving behind a gap (Kirkwood gap - gaps in
the belt where no asteroids seemed to exist) where it used to be. Asteroids or meteoroids
entering the Kirkwood gaps are booted out by Jupiter’s gravitational disruption forces so great
they completely escape the limits of the Asteroid Belt.
First, we can base a classification scheme upon meteorite samples of the asteroids.
Second, we can base our classification upon the characteristics of sunlight (albedo) reflected off
the surfaces of asteroids. (albedo = proportion of light reflected from an object; the range is 0
(perfectly black) to 1 (perfectly reflecting))
Third, astronomers and other scientists have constructed pretty sophisticated instruments
which break down the reflected light into a whole spectrum, thus collecting rough element
analyses of surfaces as well as simple albedo numbers
3 Main Groups of Asteroids:
C-type asteroids – high carbon content or ‘carbonaceous’, 75% of known asteroids; roughly
similar composition to Sun, minus the volatile elements. (located on outer asteroid belt)
S-type asteroids – high silicon or ‘silicaceous’, 17% of known asteroids.
M-type asteroids - metallic, most of the remaining asteroids.
It’s important to learn whatever we can about asteroids because:
They represent very primitive material left over from formation of the solar system
Much water and organic material came to Earth from them
Sooner or later a large asteroid impact is likely to put an end to many terrestrial
species (including humans)
carbonaceous asteroids: with dark carbon minerals on their surfaces. Have the most meaning for us of
all the different types of meteorites.
How do we get the Composition?
93% of meteorites are composed of minerals called silicates (i.e., silicon plus oxygen plus some other
elements) and most of the rest are pure metal (mostly iron with a bit of nickel).
Meteorites will have similar spectral reflectance characteristics of the asteroid they came from
To test this, investigators selected several basic kinds of meteorites and obtained laboratory
reflection of spectra of the powders and compare them with those from the asteroid.
When the reflection spectra compared with laboratory spectra of meteorite samples, it must be
remembered that the spectrum is not from a single mineral but from several at one time
This tends to "muddy" the resulting spectrum, since it is really composed of several overlapping
But for the moment, identifying the exact mineral composition at the surface of the asteroid is
not as important as finding a close spectral match between asteroids Where meteorites come from
Samples of asteroids and cores of “dead” comets
Samples blasted from the surfaces of Moon and Mars
Does the distribution of asteroid types match distribution of meteorite types collected on Earth?
The disparity between the carbonaceous chondrites, rare on Earth but plentiful in the asteroid
belt, and the ordinary chondrites, common on Earth but relatively rare in the asteroid belt,
indicates that chondrites probably came from one or at most a few parent bodies
The large numbers reaching Earth are apparently not indicative of large numbers of S-type
asteroids in space. It see