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Hubble Captures Best View of Mars Ever Obtained From Earth
Frosty white water ice clouds and swirling orange dust storms above a vivid rusty landscape reveal Mars as a dynamic planet in this sharpest view ever obtained by an Earth-based telescope. NASA's Earth-orbiting Hubble Space Telescope took the picture on June 26, when Mars was approximately 43 million miles (68 million km) from Earth -- the closest Mars has ever been to Earth since 1988. Hubble can see details as small as 10 miles (16 km) across. The colors have been carefully balanced to give a realistic view of Mars' hues as they might appear through a telescope. Especially striking is the large amount of seasonal dust storm activity seen in this image. One large storm system is churning high above the northern polar cap [top of image], and a smaller dust storm cloud can be seen nearby. Another large dust storm is spilling out of the giant Hellas impact basin in the Southern Hemisphere [lower right]. Hubble has observed Mars before, but never in such detail. The biennial close approaches of Mars and Earth are not all the same. Mars' orbit around the Sun is markedly elliptical; the close approaches to Earth can range from 35 million to 63 million miles. Astronomers are interested in studying the changeable surface and weather conditions on Mars, in part, to help plan for a pair of NASA missions to land rovers on the planet's surface in 2004. The Mars opposition of 2001 serves as a prelude for 2003 when Mars and Earth will come within 35 million miles of each other, the closest since 1924 and not to be matched until 2287. Image Credit: NASA and The Hubble Heritage Team (STScI/AURA)
The Planet Mars
American and Russian orbiters did not disclose any
canals on Mars, but did find evidence of surface erosion and dried
riverbeds, indicating the planet was once capable of sustaining liquid
water. For millions of years, the Martian surface has been barren of
water, and not subjected to the erosions Mars is a small rocky planet that developed relatively close to the Sun and has been subjected to some of the same planetary p rocesses associated with the formation of the other "terrestial" planets (Mercury, Venus, and Earth), including: volcanism, impact events, and atmospheric effects. Unlike Earth, Mars retains much of the surface record of its evolution. Layered terrains near the Martian poles suggest that the planet's climate changes have been periodic, perhaps caused by a regular change in the planet's orbit. Martian tectonism the geological development and alteration of a planet's crust differs from Earth's.
Mars has some remarkable geological characteristics including: the largest volcanic mountain, Olympus Mons (27 km high and 600 km across), in the solar system; volcanoes in the northern Tharsis region that are so huge they deformed the planet's sphericity; and a gigantic equatorial rift valley, the Vallis Marineris. This canyon system could easily fit the Grand Canyon inside it and stretches the distance equivalent from New York to Los Angeles. 'Lyell' Panorama inside Victoria Crater During four months prior to the fourth anniversary
of its landing on Mars, NASA's Mars Exploration Rover Opportunity examined
rocks inside an alcove called "Duck Bay" in the western portion of
Victoria Crater. The main body of the crater appears in the upper right of
this stereo panorama, with the far side of the crater lying about 800
meters (half a mile) away. Bracketing that part of the view are two
promontories on the crater's rim at either side of Duck Bay. They are
"Cape Verde," about 6 meters (20 feet) tall, on the left, and "Cabo Frio,"
about 15 meters (50 feet) tall, on the right. The Opportunity's targets of study during the last quarter of 2007 were rock layers within a band exposed around the interior of the crater, about 6 meters (20 feet) from the rim. Bright rocks within the band are visible in the foreground of the panorama. The rover science team assigned informal names to three subdivisions of the band: "Steno," "Smith," and "Lyell." Bigger Crater Farther South of 'Victoria' on Mars The team operating NASA's Mars Exploration Rover
Opportunity has chosen southeast as the direction for the rover's next
extended journey, toward a crater more than 20 times wider than "Victoria
Crater." Opportunity exited Victoria Crater on Aug. 28, 2008, after The crater to the southeast is about 22 kilometers (13.7 miles) in diameter and about 300 meters (1,000 feet) deep, exposing a much thicker stack of rock layers than those examined in Victoria Crater. The rover team informally calls the bigger crater "Endeavour" and emphasizes that Opportunity may well never reach it. The rover has already operated more than 18 times longer than originally planned, and the distance to the big crater, about 12 kilometers (7 miles) matches the total distance Opportunity has driven since landing in early 2004. Driving southeastward is expected to take Opportunity to exposures of younger rock layers than is has previously seen and to provide access to rocks on the plain that were thrown long distances by impacts that excavated even deeper, more distant craters.
Water on Mars
There are, however, many features on the surface of Mars which appear to have been created by great volumes of liquid. The current lack of water and erosion by liquids on Mars has kept the surface nearly unchanged for billions of years. This offers geologists a look into the ancient past of the planet as they view craters, volcanos and canyons. If there was liquid water to form the distinct features on Mars, that means that there was a medium in which life could develop. Large quantities of water are thought to be trapped underneath Mars's thick cryosphere. A large release of liquid water is thought to have occurred when the Valles Marinerisformed early in Mars's history, forming massive outflow channels. A smaller but more recent outflow may have occurred when the Cerberus Fossae chasm opened about 5 million years ago, leaving a supposed sea of frozen ice still visible today on the Elysium Planitia centered at Cerberus Palus. However, the morphology of this region may correspond to the ponding of lava flows, causing a superficial morphology similar to ice flows, which probably draped the terrain established by earlier massive floods of Athabasca Valles. Rough surface texture at decimeter (dm) scales, thermal inertia comparable to that of the Gusev plains, and hydrovolcanic cones are consistent with the lava flow hypothesis. Furthermore, the stoichiometric mass fraction of water in this area to tens of centimeter depths is only 4%, easily attributable to hydrated minerals and inconsistent with the presence of near-surface ice. More recently the high resolution Mars Orbiter Camera on the Mars Global Surveyor has taken pictures which give much more detail about the history of liquid water on the surface of Mars. Despite the many giant flood channels and associated tree-like network of tributaries found on Mars there are no smaller scale structures that would indicate the origin of the flood waters. It has been suggested that weathering processes have denuded these, indicating the river valleys are old features. Higher resolution observations from spacecraft like Mars Global Surveyor also revealed at least a few hundred features along crater and canyon walls that appear similar to terrestrial seepage gullies. The gullies tend to be in the highlands of the southern hemisphere and to face the Equator; all are poleward of 30° latitude. The researchers found no partially degraded (i.e. weathered) gullies and no superimposed impact craters, indicating that these are very young features.
November 20, 2008 -- NASA Space Craft Detects
Buried Glaciers on Mars
Scientists analyzed data from the spacecraft’s ground-penetrating radar and report in the Nov. 21 issue of the journal Science that buried glaciers extend for dozens of miles from edges of mountains or cliffs. A layer of rocky debris blanketing the ice may have preserved the underground glaciers as remnants from an ice sheet that covered middle latitudes during a past ice age. This discovery is similar to massive ice glaciers that have been detected under rocky coverings in Antarctica. "Altogether, these glaciers almost certainly represent the largest reservoir of water ice on Mars that is not in the polar caps," said John W. Holt of the University of Texas at Austin, who is lead author of the report. "Just one of the features we examined is three times larger than the city of Los Angeles and up to one-half-mile thick. And there are many more. In addition to their scientific value, they could be a source of water to support future exploration of Mars." Scientists have been puzzled by what are known as aprons – gently sloping areas containing rocky deposits at the bases of taller geographical features – since NASA's Viking orbiters first observed them on the Martian surface in the 1970s. One theory has been that the aprons are flows of rocky debris lubricated by a small amount of ice. Now, the shallow radar instrument on the Mars Reconnaissance Orbiter has provided scientists an answer to this Martian puzzle. "These results are the smoking gun pointing to the presence of large amounts of water ice at these latitudes," said Ali Safaeinili, a shallow-radar instruments team member with NASA's Jet Propulsion Laboratory, Pasadena, Calif. Radar echoes received by the spacecraft indicated radio waves pass through the aprons and reflect off a deeper surface below without significant loss in strength. That is expected if the apron areas are composed of thick ice under a relatively thin covering. The radar does not detect reflections from the interior of these deposits as would occur if they contained significant rock debris. The apparent velocity of radio waves passing through the apron is consistent with a composition of water ice. Scientists developed the shallow radar instrument for the orbiter to examine these mid-latitude geographical features and layered deposits at the Martian poles. The Italian Space Agency provided the instrument. "We developed the instrument so it could operate on this kind of terrain," said Roberto Seu, leader of the instrument science team at the University of Rome La Sapienza in Italy. "It is now a priority to observe other examples of these aprons to determine whether they are also ice." Holt and 11 co-authors report the buried glaciers lie in the Hellas Basin region of Mars' southern hemisphere. The radar also has detected similar-appearing aprons extending from cliffs in the northern hemisphere. "There's an even larger volume of water ice in the northern deposits," said JPL geologist Jeffrey J. Plaut, who will be publishing results about these deposits in the American Geophysical Union's Geophysical Research Letters. "The fact these features are in the same latitude bands, about 35 to 60 degrees in both hemispheres, points to a climate-driven mechanism for explaining how they got there." The rocky debris blanket topping the glaciers apparently has protected the ice from vaporizing, which would happen if it were exposed to the atmosphere at these latitudes. "A key question is, how did the ice get there in the first place?" said James W. Head of Brown University, Providence, R.I. "The tilt of Mars' spin axis sometimes gets much greater than it is now. Climate modeling tells us ice sheets could cover mid-latitude regions of Mars during those high-tilt periods. The buried glaciers make sense as preserved fragments from an ice age millions of years ago. On Earth, such buried glacial ice in Antarctica preserves the record of traces of ancient organisms and past climate history."
Comparison between Mars and Earth Characteristics
Mars Orbital CharacteristicsMars is smaller and, because of its greater distance from the Sun, cooler. It has seasons similar to Earth's because the tilt of its rotational axis (axial inclination) to the plane of its orbit about the Sun is about the same as Earth's. Interestingly, unlike Earth the significant eccentricity (elliptical shape) of the martian orbit means that the seasons on Mars are also affected by varying distance from the Sun. In the case of Earth, because of its almost circular orbit, our seasons result simply from the tilt of the E arth's rotation axis ... of course you knew that ....
SeasonsThe mean distance of Mars to the Sun is about 228 million kilometers. As noted above, the martian orbit is quite eccentric which leads to a difference of nearly 42 million kilometers between the furthest distance from the Sun (called "aphelion") and the closest distance ("perihelion"). As for any body in a gravitationally bound orbit, Mars travels more swiftly in its orbit when it is close to the Sun than when it is distant. As a result the duration of the four martian seasons varies one from another, unlike the case on Earth where each season lasts for just one quarter of the year. The following table compares the length of the seasons on Mars and Earth:
In accord with Newton's gravitational
law, the velocity of Mars is maximum at perihelion and minimum at
aphelion, thus the duration of seasons shows an important variability. In
the Martian northern hemisphere, winter is short and relatively "mild" The energy received by the Martian surface over the year is in direct proportion to the orbital eccentricity. The eccentricity is not fixed but, is under the gravitational influence of the other planets (especially Jupiter). The eccentricity cycles and at times the orbit is more circular. As the planet changes from an elliptic orbit to a quasi-circular one, the energy balance strongly differs from one epoch to another. We are trying to understand the changes -- we anticipate that there would be "warm periods" where increased sublimation of polar CO2 ice would lead to the release of more gas into the atmosphere, thus to a greater atmospheric pressure. As the inclination of the planetary spin axis is also subject to significant cyclic variation, we suspect that the distribution of surface heating by the Sun should have experienced cyclic change over the millenia. This cycling of the martian orbit and of its spin axis make Mars an unusually variable planet (all the planets experience cycling of their "orbital elements" but some more than others). Thus Mars may well once have been quite different from the way we see the planet today.
Polar Caps
Mars with the MGS spacecraft passing over the North Polar Cap
Click on each image for larger one.
Click on each image for larger one.
PhobosDeimos |
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The Future
Astronauts of America Foundation Title; 'We help launch the future' slogan;
Character and Name Ikky;
and
The Future Astronauts of America
Foundation Logo are
intellectual property of The Future Astronauts of America
Foundation
Where Earth tectonics involve sliding plates that
grind against each other or spread apart in the seafloors, Martian
tectonics seem to be vertical, with hot lava pushing upwards through the
crust to the surface. Periodically great dust storms occur that engulf the
entire planet. The effects of these storms are dramatic, including dunes,
wind streaks, and wind carved features.
rest of the image, other than sky and
portions of the rover, is ground within Duck Bay.
