Investigating the Near-Earth Object Population
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Investigating the Near-Earth Object Population William Bottke William Bottke Southwest Research Institute Southwest Research Institute
description
Investigating the Near-Earth Object Population. William Bottke Southwest Research Institute. When people think about “asteroids”, they mostly do not picture this:. They think of this…. Or this…. “Killer Asteroid,” National Geographic Television, 2004. Hazards From Asteroid Impacts. - PowerPoint PPT Presentation
Transcript of Investigating the Near-Earth Object Population
Investigating the Near-Earth Object Population
Investigating the Near-Earth Object Population
William BottkeWilliam BottkeSouthwest Research InstituteSouthwest Research Institute
William BottkeWilliam BottkeSouthwest Research InstituteSouthwest Research Institute
When people think about “asteroids”, they mostly do not picture this:
They think of this…They think of this…
Or this…Or this…
““Killer Asteroid,” National Geographic Television, 2004Killer Asteroid,” National Geographic Television, 2004
Hazards From Asteroid ImpactsHazards From Asteroid Impacts
Leonid Meteor Leonid Meteor ShowerShowerLeonid Meteor Leonid Meteor ShowerShower
Peekskill Peekskill MeteoriteMeteoritePeekskill Peekskill MeteoriteMeteorite
Tunguska, Tunguska, 19081908
Jupiter Jupiter Impacts Impacts
19941994
Jupiter Jupiter Impacts Impacts
19941994
Smallest Most Frequent
Smallest Most Frequent
Huge Extremely
Rare
Huge Extremely
Rare
Chicxulub, 65 Million Years Ago
Environmental ConsequencesEnvironmental Consequencesof Small Impactsof Small Impacts
A Better Way to Think A Better Way to Think About Asteroids is This…About Asteroids is This…
Meteorites are from Asteroids Meteorites are from Asteroids
Meteorites are hand-samples of asteroids (and possibly Meteorites are hand-samples of asteroids (and possibly comets) that have survived passage through our comets) that have survived passage through our atmosphere to reach Earth.atmosphere to reach Earth.
Properly analyzed, these objects can tell us about planet Properly analyzed, these objects can tell us about planet formation processes and evolution in the solar nebula.formation processes and evolution in the solar nebula.
Ordinary ChondriteOrdinary Chondrite Iron MeteoriteIron Meteorite
Fossils of FormationFossils of Formation ~10~1066 objects with diameters objects with diameters D D > 1 km between Mars and Jupiter> 1 km between Mars and Jupiter
NEOs are the “Middlemen” Between NEOs are the “Middlemen” Between Meteorites and Main Belt AsteroidsMeteorites and Main Belt Asteroids
Jupiter Family CometsJupiter Family Comets
Asteroid BeltAsteroid Belt
Near Earth Near Earth ObjectsObjects
NEOsNEOs
MeteoritesMeteorites
Some NEO Science QuestionsSome NEO Science Questions
NEO orbit and size distributions? NEO orbit and size distributions? Compositions? Internal structures?Compositions? Internal structures?
How are NEOs replenished over How are NEOs replenished over time? By what populations?time? By what populations?
How do NEOs physically evolve? How do NEOs physically evolve? What does this tell us about What does this tell us about planetesimal evolution?planetesimal evolution?
How are NEOs connected to How are NEOs connected to meteorites? Where did their parent meteorites? Where did their parent bodies originate?bodies originate?
Did NEO deliver water to the Earth?Did NEO deliver water to the Earth?
How has the NEO impact rate on the How has the NEO impact rate on the terrestrial planets changed with terrestrial planets changed with time?time?
To answer these questions, we need the most To answer these questions, we need the most accurate model of the NEO population possible.accurate model of the NEO population possible.
ItokawaItokawa
ErosEros
GeographosGeographos
How Do Near-Earth Asteroids Get Here? How Do Near-Earth Asteroids Get Here? (Part 1) (Part 1)
Jupiter Family CometsJupiter Family Comets
Asteroid BeltAsteroid Belt
Near Earth Near Earth ObjectsObjectsAsteroid CollisionAsteroid Collision
Collisions in the Asteroid BeltCollisions in the Asteroid Belt
Asteroids strike Asteroids strike one another and one another and create ejecta.create ejecta.
Most fragments Most fragments are ejected at low are ejected at low velocities (velocities (VV < 100 < 100 m/s).m/s).
Sample references: Benz and Asphaug (1999); Michel et al. (2001); Durda et al. (2004)Sample references: Benz and Asphaug (1999); Michel et al. (2001); Durda et al. (2004)
How Do Near-Earth Asteroids Get Here?How Do Near-Earth Asteroids Get Here?(Part 2) (Part 2)
Jupiter Family CometsJupiter Family Comets
Asteroid BeltAsteroid Belt
Near Earth Near Earth ObjectsObjects
Dynamical EscapeDynamical Escape
Asteroid CollisionAsteroid Collision
Koronis familyKoronis family
Bottke et al. (2001)Bottke et al. (2001)
• Observed Observed • ModelModel
Yarkovsky Effect Allows Fragments to Yarkovsky Effect Allows Fragments to Reach “Escape Hatches”Reach “Escape Hatches”
Distance From SunDistance From Sun (Further)(Further)(Closer)(Closer)
Elo
ng
ati
on
E
lon
ga
tio
n
of
Orb
ito
f O
rbit
Very Very CircularCircular
Very Very ElongatedElongated
What Happens to Them Along the Way?What Happens to Them Along the Way?
En route to the inner solar system (and Earth), En route to the inner solar system (and Earth), lots of strange things can happen to NEOs…lots of strange things can happen to NEOs…
Far view Far view Close upClose up
Asteroid Collisions Create Fragments!Asteroid Collisions Create Fragments!
The fragments can be very different from one another, implying The fragments can be very different from one another, implying different origins and evolution histories.different origins and evolution histories.
Sunlight Causes Fragments to Spin Up!Sunlight Causes Fragments to Spin Up!
Spin-Up and Disruption of a Spin-Up and Disruption of a Contact Binary by YORPContact Binary by YORP
Walsh and Richardson (2007)Walsh and Richardson (2007)
Absorbed and reemitted Absorbed and reemitted sunlight can change sunlight can change asteroid’s spin rate!asteroid’s spin rate!
This effect can produce This effect can produce strange shapes and strange shapes and even binary asteroids!even binary asteroids!
Planetary Encounters Can Pull Them Apart! Planetary Encounters Can Pull Them Apart!
Disruption of an NEO During Disruption of an NEO During Close Pass with EarthClose Pass with Earth
Gravitational (tidal) Gravitational (tidal) forces from Earth can forces from Earth can pull the asteroid apart!pull the asteroid apart!
These effects can also These effects can also produce asteroid produce asteroid satellites!satellites!
Richardson, Bottke, and Love (1998); Walsh and Richardson (2006)Richardson, Bottke, and Love (1998); Walsh and Richardson (2006)
How Can Arecibo Radar Help Us Obtain the How Can Arecibo Radar Help Us Obtain the Properties and Geologic Context of NEOs? Properties and Geologic Context of NEOs?
Direct determination of how sunlight (Yarkovsky and Direct determination of how sunlight (Yarkovsky and YORP thermal effects) affects evolution of NEOs:YORP thermal effects) affects evolution of NEOs:
This helps us understand the timing of asteroid breakups, the This helps us understand the timing of asteroid breakups, the evolution of the fragments over time, and where they will go in the evolution of the fragments over time, and where they will go in the near future.near future.
NEO physical propertiesNEO physical properties
– Precise shapes and spin rates for NEOs.Precise shapes and spin rates for NEOs.
– Detection of NEOs with satellites.Detection of NEOs with satellites.
– NEO crater histories and surface properties.NEO crater histories and surface properties.
– NEO orbital/composition distributionsNEO orbital/composition distributions
These parameters provide critical clues about NEO origins and These parameters provide critical clues about NEO origins and evolution.evolution.
Exploring Near Earth ObjectsExploring Near Earth Objects
Another way to determine the context of meteorites is to use Another way to determine the context of meteorites is to use spacecraft to return samples from an NEO. spacecraft to return samples from an NEO.
OSIRIS mission to OSIRIS mission to return samples return samples
from “1999 RQ36”.from “1999 RQ36”.
Radar Provided Unparalleled Knowledge of Radar Provided Unparalleled Knowledge of 1999 RQ361999 RQ36
Radar provided RQ36’s approximate shape, size, spin Radar provided RQ36’s approximate shape, size, spin properties, surface properties, and precise orbit, all which properties, surface properties, and precise orbit, all which were were criticalcritical for mission planning. for mission planning.
NEOs are the “Middlemen” Between NEOs are the “Middlemen” Between Meteorites and Main Belt AsteroidsMeteorites and Main Belt Asteroids
Rocks and sediments in a Rocks and sediments in a riverbed yield information on riverbed yield information on the types of material found the types of material found upstream.upstream.
NEOs are the “Middlemen” Between NEOs are the “Middlemen” Between Meteorites and Main Belt AsteroidsMeteorites and Main Belt Asteroids
Rocks and sediments in a Rocks and sediments in a riverbed yield information on riverbed yield information on the types of material found the types of material found upstream.upstream.
NEOs and meteorites tell us NEOs and meteorites tell us about the nature and evolution about the nature and evolution of bodies in the main asteroid of bodies in the main asteroid and Kuiper belts. and Kuiper belts.
ItokawaItokawa
ErosEros
