Review for Re-Test
The following are questions that were poorly answered during the first quiz. Please complete the following questions for the re-test (These MUST be answered before you take the quiz).
The following are questions that were poorly answered during the first quiz. Please complete the following questions for the re-test (These MUST be answered before you take the quiz).
- ____________ are small and icy bodies that spend most of their lives beyond the orbit of Pluto in the Oort Cloud.
- The collapsed piece of gas that formed our own solar system is called the ____________________.
- Almost _______________ asteroids have been discovered by scientists.
- There are over ___________ potentially hazard asteroids identified by the government.
- A devastating collision with a 10-km wide asteroid is hypothesized to have caused a global extinction event ____________________ years ago.
- ____________ are composed of dust and ice with a rocky core.
- A 1908 explosion of a comet in the atmosphere over ___________, destroyed forest over an area the size of a major city.
- Most Near Earth Objects come very close to Earth and almost impact. (True/False)
- How do we categorize planets like Jupiter and Uranus?
- Which element originally composed the largest percentage of the planetary nebula that formed the planets?
Near-Earth-Objects Notes
Near-Earth objects (NEOs) are asteroids or comets that approach Earth
Earth carries the scars of past impacts with asteroids and comets.
A devastating collision with a 10-km wide asteroid is hypothesized to have caused a global extinction event 66 million years ago.
Most NEOs do not come close to Earth but occasionally one may approach within the moon’s orbit.
In 2029, the asteroid Apophis is expected to come within 36,000 km of Earth
Today, more than 100,000 asteroids have been identified.
Asteroids
•Size – space pebbles to 940 km in diameter (Ceres)
•Travel at ~16 km/s (36,000 mph)
•Composed of rock and/or metals
−Meteor – asteroids that burn in atmosphere
−Meteorite – an asteroid that strikes Earth’s surface
Comets
Analysis of light from explosion on Tempel 1 revealed information on comet composition
Common compounds present including
−Cyanide
−Carbon dioxide
−Water – scientists are investigating if comets could have supplied water in Earth’s early oceans
Two types of comets
•Short-period comets
−originate in Kuiper Belt beyond Neptune
−Return to inner solar system every few years
•Long-period comets
−Originate in the Oort Cloud at the outer limits of the heliosphere
−Return orbits over decades to thousands of years
•NEO collisions with rocky planets and moons formed 2 types of impact craters
−Simple craters
−Complex craters
•Craters all feature
−Broken rocks (breccia)
−Ejecta thrown from crater
−Melted rocks
−Altered minerals
•Simple Craters
−Bowl-shaped
−Few kilometers wide
•Complex Craters
−More than 4 km diameter
−Central peak, ring structures
•Crater vs. NEO size
−An impact crater is 10-20 times larger than the colliding NEO
−Example: Manicouagan Crater, Canada
~100 km wide crater
~NEO was 5-10 km in diameter
•Large NEO impacts are infrequent
−Impacts of relatively small NEOs (~50 meters) occur at intervals of hundreds to thousands of years
−Large NEO (10+ km) impacts occur on time scales measured in hundreds of millions of years
•The Torino Scale
0 = NEO will miss Earth or burn up in atmosphere.
1 (green) = will pass near Earth but extremely unlikely to impact.
2-4 (yellow) = NEO with minor chance of impact.
5-7 (orange) = serious threat of impact, planning may be warranted.
8-10 (red) = certain collision, number corresponds to size of NEO.
Near-Earth objects (NEOs) are asteroids or comets that approach Earth
Earth carries the scars of past impacts with asteroids and comets.
A devastating collision with a 10-km wide asteroid is hypothesized to have caused a global extinction event 66 million years ago.
Most NEOs do not come close to Earth but occasionally one may approach within the moon’s orbit.
In 2029, the asteroid Apophis is expected to come within 36,000 km of Earth
Today, more than 100,000 asteroids have been identified.
Asteroids
•Size – space pebbles to 940 km in diameter (Ceres)
•Travel at ~16 km/s (36,000 mph)
•Composed of rock and/or metals
−Meteor – asteroids that burn in atmosphere
−Meteorite – an asteroid that strikes Earth’s surface
Comets
- Size – generally larger than asteroids
- Travel faster than asteroids
- Composed of dust and ice with a rocky core
Analysis of light from explosion on Tempel 1 revealed information on comet composition
Common compounds present including
−Cyanide
−Carbon dioxide
−Water – scientists are investigating if comets could have supplied water in Earth’s early oceans
- 1908 Explosion of a comet in the atmosphere over Tunguska, Russia, destroyed forest over an area the size of a major city (2,100 km2)
Two types of comets
•Short-period comets
−originate in Kuiper Belt beyond Neptune
−Return to inner solar system every few years
•Long-period comets
−Originate in the Oort Cloud at the outer limits of the heliosphere
−Return orbits over decades to thousands of years
•NEO collisions with rocky planets and moons formed 2 types of impact craters
−Simple craters
−Complex craters
•Craters all feature
−Broken rocks (breccia)
−Ejecta thrown from crater
−Melted rocks
−Altered minerals
•Simple Craters
−Bowl-shaped
−Few kilometers wide
•Complex Craters
−More than 4 km diameter
−Central peak, ring structures
•Crater vs. NEO size
−An impact crater is 10-20 times larger than the colliding NEO
−Example: Manicouagan Crater, Canada
~100 km wide crater
~NEO was 5-10 km in diameter
•Large NEO impacts are infrequent
−Impacts of relatively small NEOs (~50 meters) occur at intervals of hundreds to thousands of years
−Large NEO (10+ km) impacts occur on time scales measured in hundreds of millions of years
•The Torino Scale
0 = NEO will miss Earth or burn up in atmosphere.
1 (green) = will pass near Earth but extremely unlikely to impact.
2-4 (yellow) = NEO with minor chance of impact.
5-7 (orange) = serious threat of impact, planning may be warranted.
8-10 (red) = certain collision, number corresponds to size of NEO.