You are right that Phobos goes around Mars more than 3 times a day (3.136 = 1/.3189) as referenced to the Sun. However, at a point on the surface of Mars, Phobos would be seen just twice a day, since it has to catch
up with the planet's rotation (2.161 = 1/.3189 - 1/1.026). Since its orbit period is so short, Phobos actually appears to move in the direction that it travels, west to east, as seen from the surface of Mars. The real
motion of our own moon is slow enough that the Earth's rotation makes it appear to move east to west.
You look up your printable certificate at http://spacekids.hq.nasa.gov/2003/namequery.htm.
The DVD carries nearly 4 million names collected by NASA in the "Send Your Name to Mars" project as well as various student activities. At the center of the DVD is a Lego "astrobot" minifigure that allows children to follow the mission via the astrobot diaries of Biff Starling and Sandy Moondust. Magnets on the outer edge of the DVD will collect dust for student analysis, and children can also decode the hidden message in the black dashes around the edges of the DVD.
Announced on Sept. 19, 2005, new plans describe plans to return to the moon, and from there sketch out the efforts to go to Mars . See http://www.nasa.gov/missions/solarsystem/cev.html
(Note: http://spaceflight.nasa.gov is loaded with information on astronauts and plans for human exploration of space.)
Right now, NASA is exploring our planetary neighbors with robotic spacecraft. NASA is currently using a series of robotic orbiters and landers to search for evidence of past or present water on Mars. Finding a usable supply of water will be crucial before we can send people to the Red Planet.
For more information on Mars exploration, visit: http://marsprogram.jpl.nasa.gov/index.html.
For more information on the robotic exploration of space, visit the missions section of this website.
The so-called "face" on Mars is located in the Cydonia Mensae region at roughly 40.9 degrees North latitude and 9.45 degrees West longitude.
The Viking Lander imagers had three visible filters and three near-infrared filters. The visible filters were blue, green, and red multilayer interference filters which had very irregular spectral response, including a response to infrared light. Therefore, producing a "true" color image required the scene to be imaged in all six filters and an integrated spectral solution developed. The saturation levels at each wavelength also had to be estimated. Finally, with three visible filters, the radiance at all wavelengths not covered by these filters had to be estimated based on the response at the filter wavelengths. An array of color chips was mounted on the spacecraft to mitigate some of these problems, but accurate color reconstruction of the array in the final image, though necessary, was not sufficient to guarantee true color.
Since many of the images did not have all this information available, the colors can vary significantly from image to image based on the reconstruction techniques used.
It is believed that the closest to "true" color images of Mars (i.e., what one would see standing on the surface) show a light orange sky (due to suspended dust in the atmosphere) and a yellowish cast on the surface (due to sunlight filtering through the dust).
An independent NASA review board concluded that the most likely cause of the loss of communication with the Mars Observer was a rupture in a line in the propulsion system during the start of fuel tank pressurization. The board cautioned that "There was no specific evidence about what actually transpired during the pressurization sequence."
On August 21, 1993 the spacecraft transmitters were turned off during the final approach to Mars to protect the components against shock from the pressurization sequence. After the transmitter was turned off the tanks were supposed to be pressurized and then the transmitters turned back on and communications with Earth resumed, but no further signals were ever received on Earth.
The hypothesis is that a small amount of nitrogen tetroxide may have leaked through the check valves and condensed in the pressurization lines during the 11 month voyage to Mars. During pressurization, the oxidant would have mixed with the monomethylhydrazine fuel, causing combustion and rupture of the fuel lines. The resultant high-pressure expulsion of gasses through the rupture would have started the spacecraft spinning uncontrollably and making communication with Earth impossible.
The reason that this was considered to be the most likely scenario is that the pressure check valves were not designed for a mission in which tank pressurization took place after 11 months, but rather for a pressurization soon after launch. The decision to pressurize just before entering Mars orbit was made after the check valves were already built. It is therefore likely that some oxidant could have leaked past the valves over the 11 month period.
Other scenarios that were considered likely were: 1) A failure of the pressure regulator, causing the oxidizer tank to burst, 2) A massive short in the electrical system, or 3) Damage to the fuel tank caused by an impact from one of the pyrotechnic devices fired to open valves in the pressurization lines.
NASA has no official opinion on what the so-called "face" on Mars is. Most planetary scientists agree that the image is a combination of a natural feature and lighting conditions that formed to make ' a face.' More detailed images since the Viking missions show it to be a normal hill.
Rain: It never rains on Mars because liquid water is unstable under Martian atmospheric conditions. For why, see "Is there liquid water on Mars?"
Snow: Viking spacecraft images of the limb of Mars (i.e. the horizon, viewed from orbit) have revealed cloud layers between 20 and 80 km above the surface, apparently composed of water ice. These clouds are similar to the thin clouds above the winter Antarctic on Earth in terms of their temperature and tenuous nature. Ice particles can slowly precipitate from almost clear Antarctic skies (known as diamond dust) and collect on the surface. It may be possible that for particular locations on Mars very fine "snow" particles could fall on Mars in a manner similar to Antarctic precipitation. As yet, we do not have enough observational data to determine conclusively whether such "snow" could actually reach the Martian surface before it sublimates (i.e. turns to vapor). But theoretical calculations seem to suggest that generally such snow would not tend to reach the surface.
An alternative form of "snow" on Mars could be solid carbon dioxide snow. During winter at the poles, the atmosphere (which is predominantly carbon dioxide (CO2)) condenses. There are two extreme cases: (1) the CO2 condenses only at the cold surface to form a dense ice layer (2) the CO2 condenses in the atmosphere, perhaps on dust nucleation sites, and forms a "snow" which falls to the surface. As yet there is insufficient data to know the exact microphysics that really occurs in the Martian near-surface polar regions, but solid CO2 snow seems very likely in the polar winter. Source: David Catling's FAQ page (http://humbabe.arc.nasa.gov/mgcm/faq/faq.html), NASA Ames Research Center.
On Earth, warm air rises in the tropics, travels poleward at altitude, cools/descends in the subtropics, and returns equatorward near the surface - an overturning called the "Hadley circulation". Computer simulations suggest that such Hadley circulation also occurs on Mars. In the past, geological evidence suggests that the Earth experienced climatic changes explained by alterations in its spin axis inclination and orbit. Likewise, geological evidence also indicates that Mars underwent similar climatic changes, albeit more extreme. Consequently, Mars is a natural laboratory in which we can test our climate theories.
Major meteorological distinctions arise, of course, from the different composition and density of the two atmospheres, the smaller solar heating on Mars, and the non-existence of Martian oceans. But nevertheless, the same scientific methodology can still be used to describe each atmosphere.
In many ways, the absence of oceans on Mars, which otherwise would have a complex influence on climate, renders Martian meteorology inherently more comprehensible than the Earth's.
Beyond the purely scientific goals, Mars climate study provides vital environmental information required to maximize the safety of both robotic and human exploration in the future. The Martian atmosphere itself is the product of the sorting of the planet's initial constituents from the primordial nebula that spawned the solar system 4.6 billion years ago. Therefore, only by fully understanding the present Martian climate can we hope to deduce the climatological, geological, and (possible) biological history of Mars. To this end, our knowledge of the solar system would be enhanced. It is within this broader context that we pursue the study of Martian climate. Source: David Catling's FAQ page (http://humbabe.arc.nasa.gov/mgcm/faq/faq.html), NASA Ames Research.
The study of Martian climate and weather is scientifically desirable for comparison with the Earth and the other planets. We seek to understand what the similarities and differences can tell us about the Earth's climate and the physics of any planet's atmosphere. The Earth's climate, of course, is inextricably linked to the evolution and survival of life; the same applies to Mars if it has/had life.
The climate of a planet is determined by planetary "constants," which, in turn, derive from a planet's formation and subsequent evolution. Mars is remarkably similar to the Earth in its rotation rate and axial tilt (see picture above) so both daily and seasonal changes of the Martian atmosphere are fortuitously like the Earth's. Furthermore, both planetary atmospheres are nearly transparent to sunlight so that they are primarily heated by infrared radiation emanating from the surface below. Consequently, many of the principal parameters governing the size of the forces and the nature of the energy exchange in the Martian atmosphere closely resemble the Earth's. As a result, both planets have similar global atmospheric circulation patterns.
An example of how the study of Martian climate has directly impacted thinking about the Earth's climate (and even resulted in political repercussions) is the origin of the "nuclear winter" hypothesis. In the early 1970s, when the Mariner 9 and Viking missions revealed huge dust storms on Mars, this led to computer simulations to determine how such large dust-loadings of the atmosphere would affect the surface temperature on Mars. Such computer simulations have also been applied to Earth's climate, loaded with airborne particles from a large nuclear weapons exchange. It was realized that the Earth's climate would be drastically affected by cooling and that nuclear war was even more of a no-win situation than previously thought. Moreover, there are numerous examples of meteorological/climate phenomena that apply to both Mars and the Earth. In the winter hemisphere, for example, waves of high and low pressure systems travel eastwards on Mars just as they do on Earth.
Terrestrial systems have associated "frontal systems" - sharp boundaries between cold and warm air masses. Fronts also occur on Mars. Terrestrial storms occur in preferred zones, e.g., in the midlatitude oceans of the northern hemisphere. Such "storm zones" also (theoretically) occur in the northern midlatitudes on Mars in low relief regions.
Mars shows abundant signs of past volcanic activity spanning a wide range of geologic ages and volcanic rocks cover most of the surface. The most obvious features are the large volcanoes in the Tharsis province, such as Olympus Mons, and the extensive plains formed from volcanic flows. Volcanoes are also important to climate science: in the past they would have injected large quantities of gases into the Martian atmosphere, e.g. water vapor, carbon dioxide (CO2), and sulfur dioxide (SO2), which may have enhanced greenhouse warming on early Mars.
From the viewpoint of comparison with Earth, the interior of Mars has cooled more rapidly over geological time because Mars is smaller, only half the diameter of Earth, and only 1/10th the mass. Consequently, the heat flow from the interior of the planet, which causes volcanic and geothermal activity at the surface, is now so small that there are no known active volcanoes.
Estimates of ages of Martian volcanic features can be made from the number of impact craters and the layering relationships of various geologic units. Published estimates of the formation age of the surfaces of the Tharsis volcanic shields range from 2500 million years ago to only 100 million years ago - so there is a great deal of uncertainty. Recent imaging data from NASA's Mars Global Surveyor suggests that the great shield caldera of Arsia Mons is no older than 40-100 million years old, based on the lack of impact craters. Globally, volcanic activity is thought to have peaked about 3000-3500 million years ago (when the Martian ridged plains were formed) and the rate has since dropped off exponentially so that today there are no signs of active volcanoes. Nevertheless, extrapolation of the volcanic activity curve to present day suggest that geothermal activity may not have completely vanished; it is estimated that a lava flow has been extruded about once every 10,000 years in the past few hundred million years.
If there are any "hot spots" on Mars they would provide a source of energy. Thus they would be of great interest scientifically since a hot spot is where liquid water and possible vestiges of life are most likely to be found near the surface.
Source: David Catling's FAQ page
(http://humbabe.arc.nasa.gov/mgcm/faq/faq.html), NASA Ames Research Center.
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