# Solar System, technical/Mars

Mars is the fourth planet from the Sun, and it can come closer to Earth than any planet except Venus. A great deal of mythology, science, and technology is associated with it.

## Mythology

In Roman mythology, Mars is the name of the god of war. In Hindu mythology, he is considered to bring good will.

## Physical features

The soil of Mars is a rusty, tawny red. This is due to the large amounts of oxidized iron present. The Martian volcano Olympus Mons, meaning "Mount Olympus", is the tallest known mountain in the Solar System (standing about three times taller than Earth's Mount Everest.) Other large volcanoes are Ascraeus Mons, Pavonis Mons and Arsia Mons -- all of which lie in a nearly straight line. Mars has two small moons, named Phobos (meaning fear) and Deimos (meaning dread).

## Exploration

Scientists are searching extensively to find out if there is life on Mars. The Viking probes, sent in the 1970s, found no conclusive evidence of life. There is a possibility, however, that in the past, Mars was warmer and had liquid water. Most of the current exploration on Mars is geared toward discovering the current presence of water ice and the former presence of water in liquid form. NASA spacecraft have had a notoriously low success rate in reaching Mars, although in recent times, more and more missions have been successful. Several spacecraft are orbiting the planet, including Odyssey, the Mars Reconnaissance Orbiter, and the European Space Agency's Mars Express. Current spacecraft on Mars are the Mars Exploration Rovers: Spirit and Opportunity. The next mission to land will be the Mars Science Lab (MSL), slated to launch from Earth in late 2011 and land on the Red Planet in 2012. In addition, Russia is launching a mission to Phobos that will include a Chinese orbiter named Yinghuo-1. This is set to launch around the same time as MSL.

## Statistics

Diameter: 6,786 km (4,217 mi.)
Length of day: 24 hours, 39 minutes
Length of year: 687 days
Distance from Sun: 228,000,000 km (142,000,000 mi.)
Moons: Two, Phobos and Deimos
Diameter of Phobos: 27 km (17 mi.)
Diameter of Deimos: 15 km (9 mi.)

## X-ray astronomy

At right is an X-ray image of Mars. X-radiation from the Sun excites oxygen atoms in the Martian upper atmosphere, about 120 km above its surface, to emit X-ray fluorescence. A faint X-ray halo that extends out to 7,000 km above the surface of Mars has also been found. The Chandra X-ray Observatory image on the right is the first look at X-rays from Mars.
In X-ray astronomy, Mars is a gas dwarf.

## Violet astronomy

"Phoenix touched down on the Red Planet at 4:53 p.m. Pacific Time (7:53 p.m. Eastern Time), May 25, 2008, in an arctic region called Vastitas Borealis, at 68 degrees north latitude, 234 degrees east longitude."
In the image at right "is an approximate-color image taken shortly after landing by the spacecraft's Surface Stereo Imager, inferred from two color filters, a violet, 450-nanometer filter and an infrared, 750-nanometer filter."
The "image shows a polygonal pattern in the ground near NASA's Phoenix Mars Lander, similar in appearance to icy ground in the arctic regions of Earth." Noteworthy is the blue to violet faces of many of the small stones shown.
"As the sun rises over Noctis Labyrinthus (the labyrinth of the night), bright clouds of water ice can be observed in and around the tributary canyons of this high plateau region of Mars. This color composite image, reconstructed through violet, green, and orange filters, vividly shows the distribution of clouds against the rust colored background of this Martian desert."
"Scientists have puzzled why the clouds cling to the canyon areas and, only in certain areas, spill over onto the plateau surface. One possibility is that water which condensed during the previous afternoon in shaded eastern facing slopes of the canyon floor is vaporized as the early morning sun falls on those same slopes. The area covered is about 10,000 square kilometers (4000 square miles), centered at 9 degrees South, 95 degrees West, and the large partial crater at lower right is Oudemans. The picture was taken on Viking Orbiter 1's 40th orbit."
At lower right is a view of the Martian atmosphere and surface taken through the Viking Orbiter violet filter to illustrate the dramatic clarity "of the atmosphere in the region east and northeast of the Argyre basin during winter in the southern hemisphere. [The image is] taken just after the winter solstice when solar heating is minimal."
The second image at the left is a true color image of Mars showing extensive areas of blue to violet surface materials. The data came from the Mars Global Surveyor during a flyby around Mars.

## Blue astronomy

"The Mast Camera (Mastcam) on NASA's Mars rover Curiosity showed researchers interesting internal color in this rock called "Sutton_Inlier," which was broken by the rover driving over it. The Mastcam took this image during the 174th Martian day, or sol, of the rover's work on Mars (Jan. 31, 2013). The rock is about 5 inches (12 centimeters) wide at the end closest to the camera. This view is calibrated to estimated "natural" color, or approximately what the colors would look like if we were to view the scene ourselves on Mars. The inside of the rock, which is in the "Yellowknife Bay" area of Gale Crater, is much less red than typical Martian dust and rock surfaces, with a color verging on grayish to bluish."
"[T]he Chemistry and Camera (ChemCam) instrument zapped [the rock known as "Jake Matijevic"] with its laser on Sept. 21, 2012, and Sept. 24, 2012, which were the 45th and 48th sol, or Martian day of operations. ... black and white images were taken by ChemCam to look for the pits produced by the laser. ... [Later] the Alpha Particle X-ray Spectrometer trained its view. ... This image was obtained by Curiosity's Mast Camera on Sept. 21, 2012 PDT (Sept. 22 UTC), or sol 46. [For natural color, processors] white-balanced the color in this view to increase the inherent differences visible within the rock." Other bluish rocks can just be seen. Curiosity removed the Martian dust from "Jake Matijevic" before photographing.
"On Sol 20 of its journey, Mars Exploration Rover Opportunity woke up around 5:30 in the martian afternoon to watch the sunset. A series of five sets of three-color images from the rover's panoramic camera was acquired looking toward the southwest. Each set used an infrared, green and violet filter, rather than the human red-green-blue, so that the maximum panoramic camera wavelength range could be covered by the observations, enhancing the scientific value of the measurements."
"A color image was made [at lower right] from the first post-sunset sequence of calibrated color images, with the color balance set to approximate what the sunset color would have looked like to the human eye. The color seen in this first post-sunset image was then used to colorize each image in the sequence. Approximately one-minute gaps between consecutive color images meant the Sun's position changed within each color set, so the images had to be manually shifted to compensate for this motion. In this fashion, the position and brightness of the Sun are taken from each individual image, but the color is taken from a single set of images. The images were then combined into a movie where one color set fades gracefully into the next. Analysis of the five color sets shows that there were only small color variations during the sunset, so most of the real variations are captured in the movie."
"The rapid dimming of the Sun near the horizon is due to the dust in the sky. There is nearly twice as much dust as there was when the Mars Pathfinder spacecraft, which landed on Mars in 1997, imaged the sunset. This causes the Sun to be many times fainter. The sky above the Sun has the same blue tint observed by Pathfinder and also by Viking, which landed on Mars in 1976. This is because dust in the martian atmosphere scatters blue light forward toward the observer much more efficiently than it scatters red light forward. Therefore, a "halo" of blueish sky color is always observed close to the Sun. We're only seeing half of this halo in the movie, because the other half is below the horizon."
At lower left is a natural color image taken by HIRISE. These layered deposits may have formed through the accumulation of sediment that were transported into this crater by blowing wind or flowing water.

## Crater astronomy

"Near the lower left corner of this view [at right] is the three-petal lander platform that NASA's Mars Exploration Rover Spirit drove off in January 2004. The lander is still bright, but with a reddish color, probably due to accumulation of Martian dust."
"The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter recorded this view on Jan. 29, 2012, providing the first image from orbit to show Spirit's lander platform in color. The view covers an area about 2,000 feet (about 600 meters) wide, dominated by Bonneveille Crater. North is up. A bright spot on the northern edge of Bonneville Crater is a remnant of Spirit's heat shield."
"The shield volcano, Olympus Mons [shown in the second image at right] (Mount Olympus), at 27 km is the second highest known mountain in the Solar System. It is an extinct volcano in the vast upland region Tharsis, which contains several other large volcanoes. Olympus Mons is over three times the height of Mount Everest, which in comparison stands at just over 8.8 km."
"Rampart craters are a specific type of Martian impact crater which are accompanied by distinctive fluidized ejecta features. A Martian Rampart crater displays an ejecta with a low ridge along its edge. Usually, rampart craters show a lobate outer margin, as if material moved along the surface, rather than flying up and down in a ballistic trajectory. The flows sometimes are diverted around small obstacles, instead of falling on them. The ejecta look as if they move as a mudflow. Some of the shapes of Rampart craters can be duplicated by shooting projectiles into mud. Although rampart craters can be found all over Mars, the smaller ones are only found in the high latitudes where ice is predicted to be close to the surface. It seems that the impact has to be powerful enough to penetrate to the level of the subsurface ice. Since ice is thought to be close to the surface in latitudes far from the equator, it does not take too strong of an impact to reach the ice level. So, based on images from the Viking program in the 1970s, it is generally accepted that rampart craters are evidence of ice or liquid water beneath the surface of Mars. The impact melts or boils the water in the subsurface producing a distinctive pattern of material surrounding the crater."