Order of the Planets from the Sun Acronym- My Very Educated Mother Just Served Us Nachos. Planets- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

Requirements to be Called a Planet! Round Revolve around the sun Orbit the sun in the same plane/position as the other planets.

Mercury The closest planet to the sun Has the shortest revolution- 88 days The smallest planet No moon

Venus The hottest planet because it is so close to the sun and has a thick atmosphere to hold in energy- greenhouse effect Visited by the Russian probe Venera Covered in Volcanoes

Earth The living planet; the only planet we know that has life

Mars Most similar to earth (in diameter, mass, rotation and revolution, temperature) Has 2 moons Has some water in the frozen ice caps at its north and south poles

What separates Inner planets (Terrestrial) from the outer planets (Jovian) Asteroid belt just beyond Mars, separates inner planets from outer planets.

Jupiter The largest planet Has at least 17 moons and 4 rings Has the Great Red Spot: A calm area surrounded by a stormy atmosphere Europa may have ocean beneath ice surface.

Saturn The least dense planet- could float on water because it is less dense than water 24 moons Rings made of chunks of ice Has a huge system of rings around it made of billions of chunks of ice & rock

Uranus Obits the sun on its side 20 moons Appears turquoise due to methane gas

Neptune The farthest planet from the sun The coldest planet Has 8 moons and 4 rings Has the longest revolution Has Great Dark Spot (a massive storm)- has vanished.

Planet Mini-Quiz! Which planet is the most similar to earth? Which planet is made mostly of methane gas? Which planet can float on water? Which planet is the hottest and why?

Solar System Debris

Comets & TNOs Comets- Dust particles in a mixture of H2O, CO2, Methane, & Ammonia. “dirty snowballs” Comets found in Edgeworth-Kuiper Belt beyond Neptune as solid body called nucleus. When a comet travels in orbit close to sun (near Jupiter), it heats & solar wind forms a Coma (tail-gas & dust). Coma trails behind comet until it moves away from the sun, then the tail is in front of the comet.

Comets Halley’s Comet has a orbital period of 76 years. Last visible from Earth in 1986 Named from Edmund Halley,18 century English astronomer-accurately predicted it’s arrival by looking at when previous comets had appeared.

Continued.. TNOs- Trans Neptunian Objects. Large bodies up to several hundred kilometers. Located in the Edgeworth-Kuiper Belt.

Asteroids Solid, rock-like masses. Irregular shape. Believed to be leftover material from solar system formation. Revolve around sun, most in circular orbit in asteroid belt. Some have long elliptical orbits.

Continued… Perihelion- closest to sun Theory: an asteroid or comet collided with Earth, causing dinosaur extinction 65 mya. Scientists are currently researching ways to prevent collisions with Earth by diverting objects before they reach Earth.

Asteroid pics

Meteors & Meteoroids Meteoroid- rock or icy fragment traveling in space. Range of sizes. Meteor- light made by a meteoroid passing through Earth’s atmosphere. (shooting star) Meteor Shower- when Earth passes through a comet’s tail & many particles from tail burn up in Earth’s atmosphere as meteors.

Meteor shower

Meteorites The part of a meteoroid that survives to strike Earth’s surface. 3 Types: Stony (94%) iron (5%) stony-iron (1%) Most abundant meteorites in Antarctic ice cap because they are exposed et the surface when wind erodes the ice around them.

Impact Craters Bowl-shaped depressions made by meteor/object that strikes a surface. About 150 known impact craters on Earth Arizona’s Barringer Meteor Crater. Earth is geologically active & erases the marks of impacts. Oldest Earth crater- Vredefort Crater in South Africa 2 byo.

What happens to comets as they approach the sun? Assignment: Write down & answer the following questions on a separate sheet of paper. What happens to comets as they approach the sun? Where are most asteroids found? Explain the difference between meteoroid, meteor, & meteorite. Most meteorites formed between 4.55 & 4.65 b.y.a., making them a little older than the oldest moon rocks. Infer why moon rocks are younger than most meteorites.