Characteristics of Near-Earth Objects

Near-Earth objects Near-Earth Objects – objects such asteroids and comets that approach Earth NEOs NEOs can strike Earth with little to no warning Chelyabinsk, Russia – 2013 – over 1000 people injured Bus-sized object Explosive force equal to 33 Hiroshima bombs

Characteristics of Near-earth objects Most asteroids and comets exist far from Earth and will likely trouble us Occasionally something happens to send an asteroid out of its normal orbit into a course that may menace Earth Depending on size, we may not detect the NEO until after it passes by

Asteroids and Meteorites Asteroids generally originate in the asteroid belt between Mars and Jupiter although they are also found in the Kuiper Belt and Oort Cloud About 90,000 identified asteroids Range from 584 miles in diameter to 164 feet in diameter Jupiter’s gravity causes collisions that periodically send asteroids out of their orbit New path may cross Earth orbit

Asteroids and Meteorites Meteors – an asteroid that burns brightly in Earth’s atmosphere Meteorite – a meteor that strike’s Earth’s surface Asteroids and meteors are either stony Similar rocks to Earth’s mantle 90 percent of known meteorites or stony material with iron or a mixture or iron and nickel

Asteroids and Meteorites All asteroids and meteors are made of the same rocks as the terrestrial planets Some meteorites appear to be fragments from Mars or our moon Ejected by earlier collisions

Asteroids and Meteorites Recognizing meteorites Dark surfaces that show signs of melting Solid and relatively smooth Rarely have holes or jagged edges Dense and magnetic Different from everything else Mission to Eros Landed on 433 Eros in 2001 Learn about geology, physical properties, and rotation of NEOs

Comets Comets – balls of ice and rock in space Released an impactor craft that crashed into comet Temple 1 in 2005 First soft landing on comet 67P/Churyumov-Gerasimenko in 2014 Comets may strike Earth but not as often as asteroids 1994 – fragments of Shoemaker-Levy 9 impacted on Jupiter First observed collision in the solar system 1908 – air burst above Tunguska, Siberia, is believed to be caused by an exploding comet

Comets What are comets made of? Ice surrounding a core of rock, similar to Pluto Icy dirtballs As a comet approached the sun it sublimates from ice to gas giving the comet its distinctive tail Temple 1 mission revealed the presence of water, cyanide, carbon dioxide, and organic material Comets may have brought water and/or organic compounds to Earth leading to evolution of life on Earth

Comets Two types of comets Short period – visit the inner solar system in intervals of 200 years or less Originate in the Kuiper Belt beyond Neptune (30-50 AUs) Comet Halley Comet Borrelly Long Period – originate in the Oort Cloud, far beyond Neptune – 50,000 AUs Comet Hale-Bopp