Meteors

1
Meteors

• rocks from space

2

• Sometimes called shooting stars,
• meteors are the light we see
• from Ionized gas
• meteors heated from friction and ram pressure
• Meteoroids relatively small space rocks (before
  hitting anything big)
• Most are about the size of a grain of sand
• Most that we see enter at About 30 - 70 km/s
• Visible at about 100 km
• Fireball or bolide very bright
• Magnatude -3 or -5
• 1mm 100km

3
Why Care?

• Astronomy test
• it's cool
• Clues to the Origin and Evolution of the Solar
  System

4
Composition

• Iron (6)
• most commonly found (they're more durable)
• Stony-Iron (2)
• Stone (92) - chondrites
• chondrules are rounded lumps of specific minerals
• carbonaceous chondrites high carbon content
  evaporate
• half of ordinary chondrites possibly from Hebe
  (asteroid)

5
Where Are They From?

• sporadic meteors don't come from anywhere in
  particular
• about 5 10 sporadic meteors per hour (the
  majority of meteors)
• meteor showers happen when earth passes through a
  clump of space rocks
• rarely result in meteorites, so are mostly very
  small
• Some are left over from the beginning of the
  solar system they've just been floating in space
  since then
• Some meteorites come from other planets or the
  moon
• knocked off (into space) by impacts
• about 1 from the moon
• micrometeorites are very small (lt1mm)
• about a ton of them hit the atmosphere daily
• The vast majority come from the asteroid belt

6
(No Transcript)
7
Theyre Fun to See!

• Avoid watching in areas with much light pollution
  (the moon is evil, too)
• Early morning is best, since thats when youre
  on the leading surface of the planet and the sun
  isn't too bright
• Someone in North America should be hit every 180
  years
• only documented case when a 9lb stone hit Mrs.
  Hodges after bouncing off her radio

8
Notable Meteorites (and Craters)

• Willamette Meteorite largest in the USA (we
  took it from the Native Americans)
• ALH84001 it came from Mars with life! (more on
  this later)
• Heat Shield Rock found on Mars
• Allan Hills 81005 first meteorite identified as
  coming from the moon
• Chicxulub Dinosaur death crater, Yucatan
  Peninsula
• Chesapeake Bay about 90 km
• Shiva hypothesized 500 km crater in the Indian
  Ocean

9
In The Movies

• (1998) Armageddon miners nuke an asteroid the
  size of Texas that's going to hit earth
• (1998) Deep impact we stop a meteor about to
  hit the earth (with ALL our nukes)
• (1979) Meteor fragments of a comet rain down
  upon the earth
• (1995) The Dig a video game wherein you dig
  apart a meteor (about to hit Earth)
• Not scientifically accurate, for many reasons

10
Could We Stop a Potential Meteorite?

• Commonly Proposed Strategies
• Nuke it
• blow it up
• deflect it
• Crash into it, to deflect it
• Push it
• focus sunlight on it, attach a propulsion engine
  to it, solar sail, gravitational tractor (most
  plausible)

11
On Other Planets

• Meteorites hit all planets
• responsible for all those craters
• Heat Shield Rock Opportunity found it on Mars

12
Dinosaur Extinctions

• A meteorite is the most widely accepted
  explanation
• 10km wide asteroid hit the Yucatan Peninsula
• 170 km wide crater
• either heated or cooled the earth (a lot)
• iridium level much higher about 65.5 million
  years ago indicates space rock

13
Life in Meteorites

• ALH84001 has biological stuff in it
• it's discovery caused a big stir
• The president even made an announcement
• it's now believed to be Earthly contaminants, not
  proof of extraterrestrial life
• Commonly contain amino acids

14
Identifying Meteorites

• Most are very heavy
• Many are metallic and are magnetic
• Irregular shape
• some enter the atmosphere without rotating,
  having a conical shape
• Fusion coating melted rock on the surface
  shiny
• Solid and Compact not full of holes
• Unusual for Region unlike the other rocks
  around
• (exceptions to all these rules)