Meteors
- a flash of light caused when a particle from space burns up in our atmosphere (NOT the particle itself)
Meteorite
A rock from space that lands on Earth
Primitive meteorite
Primitive in the sense of being remnants from the time when solid materials first condensed from the solar nebula
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2 subtypes: 1- with carbon compounds (formed farther from the Sun in the asteroid belt with lower t)
2- without carbon compounds (stony)
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Important b/c provide information about the composition about the solidified materials from which the planets formed AND their ages tell the age of our solar system
Processed meteorites
Processed in the sense of having been remade over time. Younger than primitive meteorites. Formed from asteroids that were large enough to have undergone differentiation into a core-mantle-crust structure
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2 subtypes: 1- metal-rich — fragments of a core
2- rocky compositions — fragments of mantle or crust
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Important b/c represent a form of a direct proof that large worlds really underwent differentiation
Why is there an asteroid belt?
Due to Jupiter’s gravitational effects — orbital resonance — prevents asteroids from accreting into planets
How do comet tails form?
Far form the Sun comets are completely frozen (frozen centre - nebula) —> accelerates toward the Sun —> surface t ⬆️ —> ice vaporises into gas that easily escapes comet’s weak gravity —> drags away some dust with it —» all together create a come —> a coma is pushed away ==» tail (can be millions of hundreds km)
Coma
An atmosphere around a comet that forms when the comet approaches the Sun
Types of comet tails
1– PLASMA tails — of gas that is ionised by ultraviolet light and pushed away by the solar wind ==> extends almost directly from the Sun
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2- DUST tails — of dust-sized particles that are unaffected by the solar wind and instead are pushed away by the pressure of sunlight (radioactive pressure) ==> points generally away from the Sun but has a slight curve in the direction the comet came from
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+ a comet ejects also sand- and pebbles-sized particles that are too large to be pushed away by either the solar wind or sunlight ==> they create meteor showers when Earth crosses a comet’s orbit
HOW: they enter atmosphere at such a high speed that they make the surrounding air glow with heat
Where do comets come from
1– Oort cloud - comets there have random tilts and accelerations — originally formed among the Jovian planets (later were pushed away by their grav forces_
2- Kuiper belt — comets there orbit in the same plane and direction as planets — orbit in the region in which they were formed
Pluto
— orbits Sun every 248 years
— has more elliptical and inclined orbit
— has large axis tilt -> rotates almost on its side —> underwent giant impact (suggestion only)
— has 5 moons (the largest is Charon) —> ↗️↗️
— synchronous rotation with Charon
— very cold (av t is 40K)
— has evidence of geological activity (as well as Charon) (surprisingly —> unknown source of internal heat (maybe remain some radioactive decay)
— has thin atmosphere of nitrogen, methane, carbon monoxide fromed by vaporisation of subsurface ices
Why did the majority of comets in Kuiper Belt not accreted in larger objects?
B/c of the scarcity of buildings blocks —> too spread away from each other to suffer collision
The extinction of dinosaurs
Impact of a comet or an asteroid 65 mill y ago -> carter in Mexico Yucatan Peninsula ~ 10 km)
K-Pg Boundary layer
HOW: the asteroid or a comet slammed into Earth in Mexico —> North America was devastated immediately by the large wave + debris —> debris rained all,over the globe causing fires —> lots of species died —> dust and smoke in the atmosphere blocked sunlight for years or months —> t ⬇️ —> harsh global winter —> ⬇️ sunlight stopped photosynthesis for about a year
—> acidic rains killed lots of marine species
—> the impact boosted a period of intense volcanic activity
Features (evidence) of K-Pg Boundary layer
1) iridium
2) shocked quartz (formed under high-pressure)
3) rock droplets
4) soot
