For centuries, earthlings made up stories about martians -- from ancient, advanced civilizations to little green men to cartoon star Marvin the Martian. Since we knew virtually nothing about the red planet, it was easy to fill in the gaps with pure fantasy. Direct observation yielded little -- this pre-World War I illustration by Sir Percival Lowell was considered one of the best guesses until the 1960s, when unmanned spacecraft reached the planet. Even then, drawing was involved, as you'll see in the next picture.
Image Credit: NASA
Do not adjust your set -- this really is the first TV image from Mars. When the Mariner 4 spacecraft flew by Mars in November 1964, it sent back video images in digital form. LBJ-era technology took a long time to fully process those numbers as pictures. Mission scientists grew impatient and printed the numbers on strips of paper, which they colored in with pastels. Then they presented their handiwork to Jet Propulsion Laboratory Director William H. Pickering. Next up, see the first image ever taken on the surface.
Image Credit: NASA/JPL/Dan Goods
You are looking at the first photograph ever taken on a planet other than Earth. This image was captured July 20, 1976 by the Viking 1 lander shortly after touching down on the Martian surface. Viking 1 and Viking 2 were twin craft that each combined an orbiter and a lander. Designed to work for just 90 days on Mars, both Vikings succeeded well beyond researchers' expectations. The Viking 1 lander transmitted data until November 1982, more than two years after Viking 2 lander ceased operation. The landers collected data on the composition of Martian soil and atmosphere, and began NASA's on-site search for life on Mars. "The Viking mission looms like a legendary giant, an incredible success against which all present and future missions will be measured," NASA Mars Exploration Program Director Doug McCuiston said, on the occasion of the 30th anniversary of the Viking program in 2006. Next we'll see an image from one of NASA's first low-cost Mars lander spacecraft.
Image Credit: NASA
In 1997, the world was summarily astounded by the landing on Mars -- on July 4th, no less -- of NASA's Pathfinder spacecraft. Using a never-before-deployed airbag landing system, the craft bounced to a halt on the red planet and then deployed the Sojourner rover. The Pathfinder mission managed to live until the end of September 1997. Sojourner analyzed the Martian rocks, atmosphere and climate, and into the bargain it was a low-cost success for NASA. In this picture, we see a color-enhanced shot of the Martian landscape taken by the Pathfinder imager. The first pictures sent back of the barren red planet caused a sensation worldwide. In the next photo, see how another NASA rover showed the red of the red planet.
Image Credit: NASA/JPL
This is the first color image from Spirit, a Mars Exploration Rover that landed on Mars in 2004, shortly before its twin Opportunity. Like the Viking craft, these rovers didn't retire after their allotted 90 days of work. Spirit transmitted information back to NASA until 2010, and Opportunity kept rolling along after that. The rovers found strong evidence of past water activity on the planet. While NASA has continued sending craft to land on Mars, it has also not stopped observing some features from above. Next, the tallest known volcano in the solar system.
Image Credit: NASA/JPL
Mars is roughly half as big as Earth, but it has the solar system's largest volcano. This is Olympus Mons (Mt. Olympus), a shield volcano three times as tall as Mt. Everest, in a mosaic image from the Viking 1 Orbiter in 2000. At 374 miles (624 km) in diameter, the volcano is about the same size as the state of Arizona. With less gravity on Mars than on Earth, the lava was freer to spread out. In our next image, another dramatic feature of the Martian landscape.
Image Credit: NASA/JPL
This is Victoria Crater near the Martian equator, in a 2006 enhanced-color image by the Mars Reconnaisance Orbiter. It is about a half-mile (800 m) across. Impact craters -- created by falling meteorites -- are of interest to scientists because they expose layers and layers of the planet's crust. NASA scientists explored this crater both from a distance and up close, as you'll see in the next picture.
Image Credit: NASA/JPL-Caltech/University of Arizona/Cornell/Ohio State University
A detail of the previous image shows MARS Exploration Rover Opportunity at work, 22 months into its mission on Mars. The Mars Reconnaissance Orbiter could detect the rover's tracks and even the shadow from its camera mast. Do you know what the rover saw?
Image Credit: NASA/JPL/UA
This cliff is called Cape Verde. Mars Exploration Rover Opportunity took this approximate true-color picture Oct. 20, 2007. The slight haziness of the image is due to dust on the rover's camera. To see the rover's next destination, check out the next image.
Image Credit: NASA/JPL-Caltech/Cornell
A view across the Meridiani Plain toward the Eastern rim of Endeavor Crater. After two years of work at Victoria Crater, Opportunity began to make its way to the Western rim of Endeavor Crater, and this is an approximately true color image from the journey. Next, leap to the Martian North Pole.
Image Credit: NASA/JPL-Caltech/Cornell University
A May 2010 image from the Mars Global Surveyor shows the Northern polar ice cap of Mars. The Martian ice caps, unlike those on Earth, contain some frozen water but are mostly frozen carbon dioxide, or dry ice. The snake-like dark band to the right is Chasma Boreale, a canyon almost as long as the Grand Canyon and in some places 1.2 miles (2 kilometers) deep. See it up close in the next photo.
Image Credit: NASA/JPL-Caltech/MSSS
This is an eastward-looking view of Chasma Boreale, in a composite picture made of images taken by NASA's Mars Odyssey orbiter between December 2002 and February 2005. The canyon's walls reach about 4,600 feet (1,400 meters) above its floor. The northern polar ice cap has evaporated to reveal sheets of sand and the wind has pushed loose sand down the canyon into dunes and toward the camera. Next we'll take another view of the Martian north pole using thermal imaging.
Image Credit: NASA/JPL-Caltech/ASU
Here, a sea of dark, wind-shaped, dunes surrounds the northern polar cap. According to NASA, the dunes span an area about the size of Texas. Cooler temperatures in this picture are shown in bluer tints, and the warmer features are shown in yellows and oranges. This image covers an area 19 miles (30 kilometers) wide. To journey to the south pole of Mars, check out the next picture.
Image Credit: NASA/JPL-Caltech/ASU
These veiny items near the south pole of Mars look like sand hills or mutant spiders, but are actually ridges cut into the soil by dry ice. Just as on Earth, dry ice sublimates -- it changes directly to gas from ice, without going through a liquid phase. In the Martian spring, as the ice begins to warm up, gas from the bottom of the ice forces out to find a place to escape into the atmosphere, cutting these channels along the way. Next, see something on Mars that isn't from Mars.
Image Credit: NASA/JPL-Caltech/University of Arizona
A lone rock in a lonely place: NASA scientists saw this object in this image captured by Opportunity in Sept. 2010. Thinking it might be a meteorite, they dispatched the rover to take a closer look. Using two tools on the rover's arm -- the alpha particle X-ray spectrometer and the microscopic imager -- they determined the rock is a nickel-iron meteorite. It now has the name "Oileán Ruaidh" (ay-lan ruah), after an island off Ireland's northwestern coast. But scientists don't have to go all the way to Mars to study Martian rocks, as you'll see in the following picture.
Image Credit: NASA/JPL-Caltech/Cornell University
Say hello to ALH84001, a little piece of Mars here on Earth. This Martian meteorite was discovered in Australia in 1984, fell to Earth roughly 13,000 years before that and is 4.5 billion years old. It is an early sample of the Martian crust. The small amount of carbonate in it has led scientists to a startling finding -- this rock may be evidence of life on Mars. See why on the next slide.
Image Credit: NASA
The earthworm-like object at the center of this picture has tantalized researchers. This is a scanning electron microscope image of a sample of Martian meteorite ALH84001. Though it is smaller than 1/100th the width of a human hair, and smaller than any bacteria fossils found here on Earth, researchers believe it could be a fossil of Martian bacteria. Evidence of past life on Mars continues to mount, and NASA scientists keep looking for it -- both up close and from a distance -- with ever-improving technology.
Image Credit: NASA
There's no life visible in this shot, taken from NASA's Mars Exploration rover Opportunity. The rover's navigation camera grabbed this picture of "Greeley Haven," an outcrop named in honor of planetary geologist Ronald Greeley, who was a member of NASA's Mars rover science team and many other missions.
Image Credit: NASA/JPL-Caltech
NASA's Mars Exploration rover Opportunity used its panoramic camera in November 2011 to grab this shot of a mineral vein called "homestake," which is about as wide as a thumb and 18 inches (45 centimeters) long. The vein turned out to be rich in calcium and sulfur and might even contain gypsum, a calcium-sulfate mineral.
Image Credit: NASA/JPL-Caltech/Cornell/ASU
Here the Mars Reconnaissance Orbiter affords us a look at the Jezero Crater delta. Its sediments contain clays and carbonates. Deltas like this one on ancient Mars were formed by water that carved out channels and carried sediments to lake basins. It's thanks to spectral data such as we see here that scientists are able to determine that the sediments boasted minerals that exhibited chemical alteration by water. Coming up next, we'll visit Chester Lake.
Image Credit: NASA/JPL-Caltech/MSSS/JHU-APL
On a rock outcrop that NASA scientists call Chester Lake, the robotic arm of the Exploration rover casts a shadow over the harsh landscape. The picture was taken by the rover's hazard-avoidance camera, which must have been taking note of those large rocks just up ahead. Chester Lake isn't exactly a vacation spot -- it's an exposure of bedrock on the rim of Endeavour Crater. We've got more rocks from Endeavour Crater in mind in the next picture, where we visit Ridout Rock.
Image Credit: NASA/JPL-Caltech
The rover Opportunity, from the rim of Endeavour Crater, took this raw image from its panoramic camera. The rock is referred to by NASA as Ridout Rock, and, though it looks large based on the image, it's actually only about 5 feet (1.5 meters) long. That's about the same size as the Opportunity itself. There's more fun to be had from Endeavour Crater in our next picture.
Image Credit: NASA/JPL-Caltech/Cornell/ASU
On the horizon, we see a portion of the west rim of Endeavour Crater. The crater has a diameter of about 14 miles (22 kilometers) and was more than 25 times wider than any crater Opportunity had previously approached during its staggering 90 months of operation on Mars. The picture is shown in false color in order to emphasize the differences among materials in the rocks and soil. The area in the foreground is covered with iron-rich spherules that were nicknamed "blueberries" by the NASA team. Opportunity observed them often.
Image Credit: NASA/JPL-Caltech/Cornell/ASU
A view of the lower mound in Gale Crater shows layers of rock that preserve a geologic record of environments on Mars. NASA instruments in orbit around this area have detected signatures of both clay minerals and sulfate salts, with more clay minerals present in the foreground of this picture and fewer in higher layers. This change in mineralogy may reflect a change in the ancient environment in Gale Crater. Scientists have several notions about how the minerals they detected might be indicative of changes in the amount of water on the surface of Mars. Future missions, such as the summer 2012 rover Curiosity, will use a battery of instruments to study the minerals.
Image Credit: NASA/JPL-Caltech/ESA/UA
The Mars Reconnaissance Orbiter took this image of a portion of the floor of Rabe Crater, a huge (67 miles -- 108 kilometers -- in diameter) impact crater in the Martian southern highlands. The darker areas are dunes -- accumulations of wind-blown sand -- that cover part of crater's floor. One thing that puzzles scientists is why the dunes are dark compared with the brighter layered material in the crater. It's thought that the reason for it is that the source of the dark sand is not local to this crater. Instead, the theory goes, this topographic depression acts as a sand trap that collects material being carried by winds blowing across the plains outside the crater. Next up, we'll get a glimpse of fault cracks on the Martian surface.
Image Credit: NASA/JPL-Caltech/University of Arizona
The Cerberus region of Mars has developed cracks, thanks to geological faults. The cracks carve through the planet's flat plains and mesas. This shot combines images taken between 2002 and 2004 by the Mars Odyssey Orbiter's thermal imaging system. The view spans an area 35 miles (57 kilometers) wide. If you've ever wondered what a gullied crater looks like in its youth, check out our next image.
Image Credit: NASA/JPL-Caltech/ASU
Here we see a crater that's about 4.6 miles (7.5 kilometers) in diameter and lives inside an even larger crater in the southern hemisphere of Mars. The crater doesn't have many other craters superposed on it, which is a testament to its youth. It also has very steep slopes and a sharp rim -- both attributes providing more evidence of its young age. Scientists are interested in younger, fresh craters on Mars because they help place constraints on the rate at which new impact craters and other young features have formed in recent times. This particular fresh crater contains gullies, sloped features that are believed to have required some amount of liquid water in order for them to form. NASA scientists theorize that the gullies formed after the crater did. That means that if liquid water was indeed involved in the formation of the gullies, then the water was present on the surface of Mars in more geologically recent times.
Image Credit: NASA/JPL-Caltech/University of Arizona
This image from the Mars Reconnaissance Orbiter shows a volcanic cone in the Nili Patera caldera. The cone has hydrothermal mineral deposits on its southern flanks and in nearby terrain. The entire field of light-toned material to the left of the cone is comprised of such hydrothermal deposits. The cone is about three miles (five kilometers) across at its base. The hydrothermal deposits are considered evidence for a previous environment that was warm and wet or steamy, a place that may have been habitable for microbial life.
Image Credit: NASA/JPL-Caltech/MSSS/JHU-APL/Brown Univ.
From high overhead, the Mars Reconnaissance Orbiter took a picture of the very steep side of a plateau, part of the northern limit of what's known as the Kasei Valles system, one of the largest outflow channel systems on Mars. To give a better idea of the dimensions involved, the difference in elevation between the channel's floor (seen at bottom right) and the top of the plateau (top left) is more than 0.8 miles (1,300 meters). That puts this plateau on par with the height of the Grand Canyon walls. The Kasei Valles system is far wider than the Grand Canyon, however: In certain areas, it is 300 miles (500 kilometers) wide, while the Grand Canyon at its widest is about 18 miles (30 kilometers). In our final image, coming up next, we'll see Chocolate Hills.
Image Credit: NASA/JPL-Caltech/Univ. of Arizona
Our final picture comes from the panoramic camera on the rover Opportunity. Shown is a rock NASA calls Chocolate Hills, which the rover found and examined at the rim of a young crater. Opportunity used tools on its robotic arm to analyze the texture and composition of specific areas on the rock -- with and without the dark coating. Though the image makes it look large, the rock is actually about the size of a loaf of bread. The coating on the rock may have been material that melted during the impact event that dug the crater, although analysis could not definitively conclude that was the case.
Image Credit: NASA/JPL-Caltech/Cornell University
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