SizeSmaller than Earth8 Mars would fit inside the Earth!

Days and YearsOne Earth day is 23 hrs and 56 minOne Earth year is 365 days

Days and YearsOne martian day is 24 hours and 37 minutesOne martian year is 686 earth days, almost two Earth years

SeasonsLike Earth, Mars tiltsThis tilt causes seasons

3500 km (2200 miles)

Deimos 39 km (24 miles)Phobos 69 km (43 miles)

Mars is the fourth planet from the Sun

Mars is Farther AwayEarth is 93 million miles from the SunMars is 140 million miles from the Sun

Mars is ColdHigh = 40FLow = -195F

Earth is WarmHigh = 136 F Low = -128 F

AtmosphereVery thin atmosphereMainly carbon dioxideNo oxygen

AtmosphereThickMainly nitrogen and oxygenSmall amounts of carbon dioxide

Mars is DryNo lakes, rivers, or oceans

Earth is WetEarth has oceans, lakes and rivers.

Ask students which planet this is and ask them to name features they see in the image, e.g. clouds, water, etc. Ask students which planet this is and ask them to compare it with the Earth. The most striking difference of course is the absence of oceans on Mars. Be sure to point out the polar cap (top), the large canyon at the bottom (Valles Marineris), and the three volcanoes to the left of the canyon (three circular features lined up in a row). As you may remember from the Play Dough Planets lesson, Earth is eight (8) times the size of Mars in terms of volume. In other words, eight (8) Mars could fit inside the Earth. In terms of diameter (the distance from one side of a circle to the other) the Earth is twice the size of Mars. In other words, two Mars would fit across the Earths equator. A day on the Earth is defined by how long it takes the Earth to make one complete rotation. We commonly use 24 hours as the amount of time in one day, but the actual amount of time is 23 hours and 56 minutes. One year is the time it takes for the Earth to make one trip around the sun. One Earth year is 365 days. A day on Mars is measured the same way on Earth a day (or Sol) on Mars is how long it takes Mars to rotate once. A day on Mars is very close a day on Earth, but is a little bit longer 24 hours and 40 minutes. One year on Mars is measured by how long it takes to make one trip around the sun, just like the Earth. However, one year on Mars is 686 days, almost twice as many days as a year on Earth making a year on Mars about twice as long as a year on Earth. Why is one year on Mars longer? Well have to keep going to find out.

Ask the students if the Earths poles point straight up and down. The correct answer is no, they do not. The Earth is tilted (about 25). The effect this has on the Earth is seasons. Summer (for the U.S.) occurs when the northern hemisphere is tilted towards the sun and winter occurs when the northern hemisphere is tilted away from the sun. Ask the students if they think Mars has seasons. Ask them why or why not. Yes, Mars has seasons just like the Earth. Mars has seasons because it is tilted, just like the Earth (the tilt of Mars is about 23, compared to the Earths tilt of 25). Ask students about how long does each season last on Earth. If a year on Mars is twice as long as a year on Earth, about how long do seasons last on Mars? Ask students what this is a picture of. Our moon is very big compared to the size of Earth. It is over 2000 miles across which is about half the diameter of Mars. The moon is the farthest humans have been in space. Mars has two moons Phobos and Deimos. Both moons are much smaller than Mars and our moon. Phobos and Deimos are actually two asteroids. Mars is the fourth planet from the sun, the last of the rocky planets. Obviously, Mars is farther away from the sun than the Earth. How much farther away from the sun is it? The Earth is 93 million miles away from the sun, although sometimes it is closer and sometimes it is farther away. 93 million miles is an average distance. Mars is 140 million miles from the sun, on average. Mars is sometimes closer to the sun while it is also farther away. Just as Earth and Mars vary in their distances from the sun, they also vary in their distances between each other. When Earth and Mars are on the same side of the sun, we call it opposition. Opposition occurs about every 26 months. It is during years of opposition that we launch spacecraft to Mars because it is so much closer.

Now we know how much farther Mars is from Earth. Do you think Mars is colder or warmer than the Earth? Why? Mars is cold! The highest temperature recorded on Mars was 40 degrees Fahrenheit. Ask the students if this temperature was recorded by a human. This temperature was taken by a robotic spacecraft on the surface of Mars. The lowest temperature recorded on Mars was -195 Fahrenheit. One reason Mars is so cold is because it is farther from the sun than the Earth. The Earth is warm. The highest temperature ever recorded on the Earth was 136 degrees Fahrenheit. Ask the students where they think this might have been. This temperature was recorded in Libya in 1922. The coldest temperature ever recorded on the Earth was -128 degrees Fahrenheit. Ask the students where they think this might have been. This temperature was recorded in Antarctica in 1983. Another reason Mars is colder than the Earth is because of its thin atmosphere. Ask students what they know about the atmosphere. How does it help us? The atmosphere of Mars is made of mostly carbon dioxide, about 95%. There is also no oxygen in the martian atmosphere. Ask students if humans could survive on Mars without a special suit. Why or why not? Compared to Mars, Earth has a thick atmosphere made of mainly nitrogen (79%) and oxygen (20%). There is a small amount of carbon dioxide in Earths atmosphere. Ask the students what life on Earth uses carbon dioxide (plants).

Refer back to the image of Mars at the very beginning of the presentation. Ask the students if they think there might be little rivers or lakes on Mars that could not be seen in the image. Mars is bone dry! There is no liquid water currently flowing on the surface of Mars. No lakes. No rivers. No oceans. Ask students what Mars looks like from these images. These images show Mars to be a barren world resembling a desert on Earth. However, as we all know, the Earth is wet. The Earth has lakes, rivers, and oceans. All this water is important for life of all kinds to survive.