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Asteroids
Asteroid Belt
• Between Mars and Jupiter there are a number of objects.
• All are much smaller than a planet.
• The small amount of light led them to be named asteroids.
Mars’ orbit
Main belt
Jupiter’s orbit
Minor Planets
• Ceres is the largest asteroid (933 km diameter).
• 26 asteroids have diameters greater than 200 km.
• These major asteroids show some differentiation into
layers like a planet, including lava flows.
Jupiter’s Pull
• Jupiter’s gravity keeps
asteroids from
growing too large.
• Its gravity also keeps
bands of asteroids
together with gaps like
planetary rings.
Types of Asteroids
C-type
S-type
M-type
• 75% of asteroids
• 17% of asteroids
• 8% of asteroids
• extremely dark
(albedo 0.03)
• bright (albedo
0.10 to 0.22)
• bright (albedo
0.10 to 0.18)
• oldest material,
carbon and other
minerals.
• iron mixed with
silicate rock.
• pure iron with
nickel and other
metals.
Mathilde
• Mathilde is a main-belt asteroid (66 km long).
• It is a dark type C.
• Impacts in Mathilde result in little splash at craters.
NEAR/Mathilde
Trojan Asteroids
• The law of gravity permits an orbit around the sun exactly
60º ahead of and behind Jupiter, called Lagrange points.
• Several hundred Trojan asteroids are known.
• There are small asteroids locked to other planets.
L4 Trojans
Jupiter
L5 Trojans
Near Earth Asteroids
• Asteroids nudged by Jupiter’s
gravity head into the inner solar
system.
• Many of these now have orbits
that cross the orbit of Earth.
Eros
•
•
•
•
Eros is another near-earth asteroid (30 km long).
It is a bright type S.
Impacts create boulders that rest on its surface.
The NEAR spacecraft also visited here, and safely touched
down on the surface.
NEAR/Eros
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