Chapter 9 :) Flashcards
Asteroids are _______ leftovers of planet formations
rocky
whats the largest asteroid?
Ceres with a diameter of 1000 km
are large asteroids or small ones more common?
small asteroids
how many asteroids are listed in catalogs?
150,000
how many asteroids have a diameter greater than 1 kilometer?
over a million
all the asteroids in the SS would not add up to a what?
to even a small terrestrial planet
most asteroids orbit in a belt that is between what two planets?
mars and jupiter
what asteroids follow jupiters orbit?
Trojan Asteroids
orbit of ____________ asteroids cross earths orbit
near-Earth
rocky planetesimals between mars and jupiter did not what?
accrete into a planet
jupiter’s gravity through influence of ______________, stirred up asteroid orbits and prevented their accretion into a planet
orbital resonances
define meteorite
a rock (fragment of an asteroid) from space that falls Earth’s atmosphere
define meteor
bright trail left by a meteorite. pea size particles, do not hit the earth’s surface
Primitive Meteorite
Unchanged in composition since they first formed (condensed and accreted) 4.6 billion years
Processed Meteorite
younger, have experienced processes like volcanism and differentiation. (high metal content: chunks of the core of larger asteroid that was shattered by a collision)
Metal rich processed meteorite-
made of iron and other metals that came from shattered asteroid’s core
rocky processed meteorite
resembles volcanic rocks formed on earth
a _____ meteorite arrive from the moon and mars
few
from what does the asteroid fragments differ?
composition
composition is a cheap way to what
acquire moon rocks and mars rocks
where did comets form?
beyond the frost line
what are comets?
icy counterpart to asteroids
the nucleus of a comets is like…
a dirty snowball
most comets do not have what?
tails
most comets remain what in the outer solar system?
frozen
only comets that enter the inner solar system
grow tails (pointing away from sun)
what is coma?
an atmosphere that comes from heated nucleus
what is (straight) plasma tail?
gas escaping from coma, pushed by solar wind
(curved) dust tail is
pushed by photons
comets eject small particles that..
follow the comet around in its orbit and cause meteor showers (pea sized particle from a comet) when earth crosses the comet’s orbit
only a tiny number of comets enter the _______
inner solar system; most stay far away far from the sun
oort cloud
on random orbits extending to about 5,000 AU
Kuiper belt
on orderly orbits from 30-100 AU in a disk of solar system
where do kuiper belt comets form?
the kuiper belt
Kuiper belt is…
- a flat plane aligned with the planetary orbits
- orbiting in the same direction as the planets
- counterparts of asteroid belt
what comets where once closer to the sun? why were they kicked farther out?
oort cloud comets, kicked farther out by gravitational interactions with jovian planets.
oort cloud comets
extremely elliptical orbit, orbiting in any direction
spherical distribution
is pluto a planet?
discovered in 1930 (only 80 years ago)
- much smaller than 8 major planets
- not a gas giant like outer planets
- has icy composition like comet
- very elliptical, inclined orbit
- pluto has more in common with comets than with any major planet
what is eris?
an iceball larger than pluto, discovered in 2005
what is the name of eris’ moon?
Dysnomia
where is there many icy objects like pluto on elliptical, inclined orbit?
Beyond neptune
how big are the biggest icy objects beyond neptune?
the size of earths moon
earth has been hit by many…
asteroids and comets
major impacts on earth are very…
rare
a major impact is only a
matter of time, not IF but WHEN
major damage by an impact
in tens to hundreds of years
