56 Missions to Mars-Low

MISSIONS TO MARS FOCUS Question How can technology help us learn about Mars?

THE RED PLANET Mars is Earth's neighboring planet in space. This rocky planet circles, or orbits, the Sun between Earth and Jupiter. Mars is a cold world about half the size of Earth. It has two small moons. Mars looks red because the soil and rock contain the rusty mineral iron. Ever since people first noticed it in the night sky, we have been studying Mars. Doing so may help us understand how Earth and the rest of the solar system formed and whether there is life on Mars. COMPARING EARTH AND MARS Earth Mars distance from sun 93 million miles 142 million miles size (diameter) 7,926 miles 4,220 miles length of year 365.25 days 687 Earth days length of day 23 hours, 56 minutes 24 hours, 37 minutes gravity 2.66 times that of Mars 0.375 times that of Earth temperature average 57°F average 81°F number of moons 1 2

LIFE ON MARS? Mars doesn't seem to have life today, but it may have had life in the past. The chance of finding signs of life is a big reason we study Mars. Water is very important to living things. Scientists look for it on other planets. Billions of years ago, Mars was likely covered in oceans and flowing rivers. Now Mars is very cold and has mostly ice. But salty liquid water flows in some areas during the warmer season. We have learned much about Mars from building and flying spacecraft and probes. With each mission, we get a step closer to understanding the Red Planet.

FLY... BYE! More than forty probes from different countries have flown by or landed on Mars. The first ones reached space atop rockets. The rockets put them into orbit around the Sun. Scientists used careful timing so each probe would fly by Mars. In 1965, Mariner 4 took the first photos of Mars from space. They showed many craters on the surface. In 1969, Mariner 6 and 7 sent back hundreds of photos. The two probes took close-up pictures of dark grooves. They looked like human-made "canals." Wowser! Martian "canals" are really dried-up riverbeds. They were not built by Martians!

ROUND AND ROUND THEY GO The next probes did more than a flyby. They entered Mars's orbit for a closer, longer look. Mariner 9 mapped the entire surface in 1971. It saw many canyons, craters, and inactive volcanoes. Mariner 9 was the first to spot Mars's two moons. Mars Global Surveyor entered orbit in 1997. It found new signs of water on Mars. The surface has paths left by flowing water! Word Wise Just as a moon orbits a planet, so do orbiting probes. In fact, they are both called satellites. Moons are natural satellites. Probes are artificial, or human- made, satellites.

TOUCHDOWN! Viking 1 and 2 made history by both landing on Mars in 1976. First, they entered orbit. Then they sent landers down to different parts of the planet. Protective shells kept them safe on touchdown. They then went to work taking photos and doing soil and air tests. Mars Pathfinder bounced onto the surface in 1997. It floated down on a parachute Airbags protected the craft during its landing. Inside was the first Mars rover. It cruised the surface and sampled soil and rocks Studying the rocks. taught us that Mars was once much warmer—and wetter. In fact, Mars Pathfinder had landed in the site of an ancient flood. Do You Know? Mars Pathfinder's airbags were made of special fabric that wouldn't tear when the lander hit the rocky surface.