Lecture 10 Flashcards
1
Q
How was the solar system formed?
A
- scientists believe a cloud of gas and dust in space was disturbed by a supernova
- 4.6 billion years ago
- the nebular hypothesis: the explosion made waves in space
- this caused the formation of a solar nebula (a flattened cloud of gas and dust)
2
Q
How do planets form?
A
- the centre of the solar nebula grew hotter resulting in the formation of the Sun
- the outer edges cooled causing clumps of particles to stick together and form planets
3
Q
What is a galaxy?
A
- a cluster of billions of stars
- our solar system makes up a tiny portion of the Milky Way Galaxy
4
Q
What is a star?
A
-a hot glowing ball of gas that generates energy by converting hydrogen to helium
5
Q
Describe the Sun
A
- the Sun is located approximately 30 quintillion km from the centre of the Milky Way Galaxy
- it takes light nearly 100 000 years to travel from one side of the galaxy to the other
- in the core, temp is 15 000 000 degrees Celsius
- the outermost part of the Sun is called the photosphere and it is 6000 degrees Celsius
- energy from the Sun controls the Earth’s climate system
- the Earth only receives one two-billionths of the Sun’s total energy
6
Q
What is contained in the solar system?
A
- the solar system is composed of 8 planets, 60 moons, and millions of bolides
- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
7
Q
What is the life cycle of stars?
A
- the Sun is closest star to Earth and it has a life expectancy of 10 billion years
- at the end of the life cycle of a star, massive amounts of energy are released (supernova)
8
Q
What is a bolide?
A
- extraterrestrial bodies that originate in outer space
- asteroid: rocky metallic material in space 10m to 1000km in diameter originating in the asteroid belt (between Mars and Jupiter)
- meteoroid: smaller objects in space up to 10m in diameter
- meteor: a meteoroid that has entered Earth’s atmosphere
- meteorite: a meteor that strikes the Earth’s surface
- comet: these are distinguishable by a glowing tail of gas and dust
- it is believed that comets formed in an area outside of the solar system called the Kuiper belt
9
Q
What are comets?
A
- comets are composed of a rocky core of gas and ice
- they create light as gases are released as the comet is heated by solar radiation
- Halley’s comet is the most famous because it is visible with the naked eye and passes close to Earth every 75 years
- it will next be visible in 2061
10
Q
What are airbursts?
A
- bolides travel at velocities of 12-72km/s
- as they heat up upon entering Earth’s atmosphere, they produce bright light
- the object may explode in an airburst at an altitude between 12km and 50km or it will collide with Earth’s surface
11
Q
What is the Tunguska airburst?
A
- the explosion destroyed over 2000 square km of forest in a sparsely populated area of northeast Russia in 1908
- scientists have determined it was an airburst because no crater has ever been found
- the asteroid responsible is believed to be 25 to 50m in diameter
12
Q
What is the Chelyabinsk airburst?
A
- on feb 15 2013 a meteor exploded over the city of Chelyabinsk in southwest Russia
- it is the largest bolide to enter Earth’s atmosphere since the Tungaska airburst
- over 1500 people were injured, mainly from broken glass
13
Q
What are impact craters?
A
- these provide evidence of past meteorite impacts
- a layer of debris called an ejecta blanket consists of rock fragments that were blown out of the crater on impact
- craters today are not as deep as the original impact crater due to erosion and fragmented rock falling back into it shortly after impact
- this rock is referred to as breccia
14
Q
What are simple vs complex impact craters?
A
- simple craters are less than a few km in diameter and do not have an uplifted centre
- a complex crater consists of a rim that collapses under exteme faulting and a centre floor that rises following impact
- complex craters are generally greater than 6km in diameter
15
Q
What is the Manicouagan crater?
A
- this complex impact crater is 100km in diameter and is one of the 5 largest in the world
- it is located in central Quebec and was formed approx 214 million years ago
- faulting caused the rim to collapse and the rock has eroded to form a ring-shaped lake
16
Q
What is the Chesapeake crater?
A
- this is a crater that was not discovered until subsurface imaging and drilling revealed its presence
- the crater formed 35.5 million years ago
- since then, it has been overlain by sediment and seawater as sea levels have risen
17
Q
Why are craters much more common on the Moon than on Earth?
A
- most impacts with Earth are over oceans where craters are not produced
- impacts with Earth’s land have been eroded or buried and thus have more subtle features than moon craters
- smaller bolides often burn up and disintegrate in Earth’s atmosphere before striking its surface
18
Q
Describe the Shoemaker-Levy comet?
A
- this comet entered Jupiter’s atmosphere in 1994
- massive amounts of energy were released, and gas plumes were produced as 21 fragments of the comet collided with Jupiter
- after this impact, it was universally accepted that a similar impact could one day strike Earth
19
Q
What are mass extinctions?
A
- extinctions coincide with boundaries of geologic periods on the geologic time scale
- these are usually consistent with abrupt changes in climate from plate tectonics, volcanism, bolides, or human impacts
- there have been 5 major extinctions during the past 550 million years and a 6th is occurring today
- the extinction today is occurring due to climate change
20
Q
What is the K-T boundary mass extinction?
A
- it occurred 65 million years ago from the abrupt cooling caused by an asteroid impact
- it is named for the boundary separating the Cretaceous and Tertiary Periods
- in some languages, Cretaceous is spelled with a “K”
- this event caused extinction of the dinosaurs which had been at the top of the food chain for 100 million years
- it caused the extinction of 70% of all plant and animal species that existed at the time
- the abrupt cooling caused many plant species to become extinct which then caused animals which ate those plants to become extinct and so on up the food chain
21
Q
How was the K-T boundary mass extinction impact discovered?
A
- scientists found large amounts of iridium in rock that was dated at 65 million years old
- iridium is a rare element on Earth, but it is found in bolides
- the hypothesis of an impact was at first criticized because no crater had been found
- crater was discovered in 1991; it is 180km in diameter and was found underlying sediments and sea water
- it is located in the Yucatan Peninsula in Mexico and was given the name Chicxulub Crater
- analysis of the crater suggests the impact produced 10 000 times the energy of the entire nuclear arsenal of the world today
22
Q
What hazards are linked to bolide impacts?
A
-bolide impacts can trigger tsunamis, earthquakes, landslides, and cause climate change
23
Q
What is the risk of bolide impacts?
A
- as long as an asteroid remains in the asteroid belt (between Mars and Jupiter) it poses no hazard to Earth
- the orbital path of an asteroid could be disturbed by a collision with another object
- it is estimated there are about 1100 asteroids larger than 1km in diameter with near-Earth orbits
- scientists estimate that an urban area would be destroyed once every 30 000 years by an asteroid similar in size to the Tunguska airburst (which has a 1000-year recurrence interval)
- a Tunguska-sized event is projected to occur every 1000 years; however, only 1 out of 30 times would it impact an urban area
24
Q
Given the current age of the sun, about how far is it through its lifespan?
A
- approx half (less than half)
- 4.75 ish billion years
25
Q
How do you manage the bolide impact hazard?
A
- the spaceguard survey program has catalogued all near-Earth orbits larger than 1km in diameter
- extending the inventory to bolides as small as 100m in diameter is a current objective
- if a large bolide is determined to be approaching Earth, it would be detectable decades in advance
- blowing up an approaching bolide will cause fragments to rain down and is not advisable
- nuclear explosions in the vicinity of the bolide that aim to shift its orbit is the recommended approach
26
Q
What is a supernova?
A
-the explosion of a star that has reached the end of its life cycle
