-Hundreds of thousands of asteroids have been discovered within the solar system -Discovered at a rate of about 50,000 a month
Theory of asteroid colliding with earth, thus ending reign of dinosaurs On the first day of January 1801, Giuseppe Piazzi discovered an object which he first thought was a new comet. But after its orbit was better determined it was clear that it was not a comet but more like a small planet. Piazzi named it Ceres, after the Sicilian goddess of grain. Three other small bodies were discovered in the next few years (Pallas, Vesta, and Juno). By the end of the 19th century there were several hundred. On June 30, 1908, a small asteroid 330 feet (100 meters) in diameter exploded over the remote region of Tunguska in Siberia, devastating more than half a million acres of forest. Other theories suggest that the chemical building blocks of life and much of Earth's water arrived on asteroids or comets that bombarded the planet in its youth.
To know where asteroids are, how big they are, and what the chances are that one might hit us. Provide us with needed mineral resources that may become important as we use up mineral deposits here on Earth. Astronomers are interested in asteroids because of what they can tell us about the origin and formation of the Solar System and our own Earth.
-These ground-based observations have provided a wealth of information, but by their nature revealed only so much data. Astronomers could see what was on the surface of an asteroid; -The development of rocket and spacecraft technologies provided an opportunity to send unmanned or robotic spacecraft to collect this data -Six space missions have planned encounters with asteroids Galileo, Deep Space 1 and Stardust, NEAR, MUSES-C and Dawn
C-type, includes more than 75% of known asteroids: extremely dark (albedo 0.03); similar to carbonaceous chondrite meteorites; approximately the same chemical composition as the Sun minus hydrogen, helium and other volatiles; S-type, 17%: relatively bright (albedo .10-.22); metallic nickel-iron mixed with iron- and magnesium-silicates; M-type, most of the rest: bright (albedo .10-.18); pure nickel-iron.
Albedo refers to an object's measure of reflectivity, or intrinsic brightness. A white, perfectly reflecting surface has an albedo of 1.0; a black, perfectly absorbing surface has an albedo of 0.0.
-the asteroids are so small and far away that they appear as faint stars, if they even appear at all; no asteroid is bright enough to be seen without some optical aid, -amors: asteroids are those that cross Mars' orbit; there are approximately known 1540 Amors. -Apollos: asteroids that cross Earth's orbits, and are sometimes called "Earth Grazers." There are approximately 2113 known Apollos. -Atens: asteroids are those whose orbits lie completely inside of Earth's. Only about 333 of these are known. -Trojans: These objects are located near Jupiter's Lagrange points (60 degrees ahead and behind Jupiter in its orbit). Several hundred such asteroids are now known, while thousands may actually exist.
Ceres is also the largest asteroid, but it is still much smaller than any of the planets. The other asteroids are smaller still. The smallest asteroids are just small rocks orbiting through space. It is estimated that the total mass of all asteroids would comprise a body approximately 930 miles (1,500 kilometers) in diameter -- less than half the size of the Moon.
What they are
• Rocky and metallic
objects that orbit the Sun
but are too small to be
• No atmospheres
• Diverse group of small
celestial bodies in the
• Known as "minor planets"
• Made of rock and metal
65 million years ago
1801 – Ceres
June 30, 1908
Why study them?
• Where are they? Could they strike earth (again?)
• Mineral Resources
• Formation of the Solar System and our own
How to study them
Six space missions
Laboratory analysis of