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The papers in this issue show that evidence for liquid water is rare and difficult to discern (see also the News story by Kerr, p. 1673). Images of supposed ancient ocean floors and riverbeds show no obvious signs that liquid water was ever present. Reexamination of some landforms implies that they have been formed by flowing lava, not water. The only locations where features seem to indicate the presence of liquid water today or in the recent past are on the rims of craters and some gullies, suggesting that heat from impacts may have been the trigger for trickles rather than a revealed water table. Radar and gravity data show that the cap on Mars' south pole now holds the largest reservoir of relatively pure water ice on the planet, and layers there and in the north polar cap reveal seasonal oscillations in climate.
These papers thus provide a tour around the martian world of water in the first 100 days or so of the main MRO mission. More will be revealed as it continues to probe the surface, including Mars' mineralogy, and focuses several instruments on its atmosphere, dust, and clouds. But there is a lot to drink already.
Other gullies, however, offer strong evidence of liquid water flowing on Mars within the last few million years, although perhaps at a different phase of repeating climate cycles. Mars, like Earth, has periodic changes in climate due to the cycles related to the planets' tilts and orbits. Some eras during the cycles are warmer than others. These gullies are on slopes too shallow for dry flows, and images from Mars Reconnaissance Orbiter's high-resolution camera show clear indicators of liquid flows, such as braided channels and terraces within the gullies.
Another new finding from that camera may help undermine arguments that very ancient Mars had a wet climate on a sustained basis. Landscapes with branched channels and fan-like deposits typical of liquid flows were found around several impact craters. Images show close association between some of those flow features and ponded deposits interpreted as material melted by the impact of a meteoroid into ice-rich crust. This new evidence supports a hypothesis that ancient water flows on the surface were episodic, linked to impact events and subsurface heating, and not necessarily the result of precipitation in a sustained warmer climate
This very high sulfur concentration reflects the heavy presence of sulfate salts (approximately 30 percent by weight) in the rocks. Chloride and bromide salts are also indicated. Such high levels of salts strongly suggest the rocks contain evaporite deposits, which form when water evaporates or ice sublimes into the atmosphere.
"With this quantity of sulfates, you kind of have to have a lot of water involved," explained Steven Squyres, principal investigator of Opportunity's science package and a professor at Cornell University....
The detection of magnesium sulfate kieserite, which is similar to epsom salt, and bromide salts were also telltale signs that water existed on the red planet. Both are evaporite minerals, and found on Earth in regions where seas evaporate over time.
Originally posted by PPLwakeUP
Before scientist believed that Mars was a very wet planet.
Geomorphic evidence suggests that recent gullies on Mars were formed by fluvial activity. Irrespective of the ultimate source of the fluid carving the gullies, we seek to understand the behavior of this fluid after it reaches the Martian surface. We numerically simulate the flow of liquid water within gully channels to determine whether liquid water can flow over sufficient distances to carve the observed channels and to place constraints on the flow rate and salinity of the water. This model is first developed to simulate a well-observed terrestrial example of channel flow in the High Canadian Arctic. This model is then applied to Mars.
We find that, contrary to popular belief, the fluvially-carved Martian gullies are consistent with formation conditions such as now occur on Mars, outside of the temperature-pressure stability regime of liquid water. Our model of the action of flowing pure liquid water produces the observed gully length distribution only at surface pressures and temperatures below the triple point where liquid water simultaneously boils and freezes and thus suggests that gullies were formed under conditions similar to present-day Mars. Numerical simulations show that pure liquid water flowing at rates of 15-60 m3/s is consistent with the observations of the gullies. The formation of gullies on Mars is inconsistent with briny fluid flows with significant flow rates because inhibiting rapid evaporation by vapor pressure suppression (or other means such as ice sheets capping the flow, or a higher pressure climate state) results in channels that are much longer than those observed on Mars. Instead, our model indicates that these fluvially-carved gullies formed in the low temperature and low pressure conditions of present day Mars by the action of relatively pure liquid water.
"The three papers provide an overwhelming case for new thinking about recent geological activity on Mars," writes Baker in an analysis of the work.
Baker said the findings support a 1991 hypothesis, then considered outrageous, that Mars has experienced episodes of cataclysmic flooding in modern times. Water is thought to have formed temporary seas, but researchers had long assumed it all evaporated into the thin Martian air.
Many scientists now agree that much of the water remained.
Streamlined forms and longitudinal grooving seen in Mars Orbital Camera (MOC) images indicate recent aqueous flooding occurred downslope (south) of the southern-most Cerberus Fossae fissure. Topography from the Mars Orbital Laser Altimeter (MOLA), in conjunction with the absence of fluvial features in MOC images immediately to the north of the Fossa, substantiate the idea that floods emanated from this fissure. The floodwater flowed southward onto the western Cerberus Plains, where it probably percolated into existing lava flows. Thus, shallow ice may still be extant beneath young lava flows in this equatorial region.
Previous studies noted the close association of geologically very recent lava flows and fluvial channels emanating from Cerberus Fossae. To assess these relationships, we outline a model of magmatic dike emplacement that involves 1) surface fractures and localized volcanic eruptions, 2) attendant cryospheric cracking to fracture the surface and release pressurized groundwater confined beneath the cryosphere, 3) effusion of water along a segment of the fracture to form Athabasca Valles, and 4) heating of the regions adjacent to the dike to cause melting and subsequent subsidence of the surface, forming late-stage pits and depressions. Previous estimates of the aqueous discharge were ~1–2 × 106 m3 s -1. Our models show that this flux could be readily accommodated by flow through adjacent dike-related cryospheric fractures at water rise speeds of ~60 m/s. The required aquifer permeability, however, is far larger than commonly encountered over similar depths and scales on Earth. This suggests that water may be transported in the subsurface by mechanism more efficient than porous flow, and/or that the previously proposed volume flux values are overestimates.
Scientists in the USA decided to retake images of the gullies to search for any sign of recent activity.
Two of those originally photographed in 1999 and 2001 then photographed again in 2004 and 2005 showed changes consistent with water having flowed down the side of the crater. The discovery was made by scientists at the San Diego-based Malin Space Systems which operated a camera aboard the spacecraft.
Writing in the journal Science, the researchers led by Michael Malin said the properties and settings of the deposits in the gullies are consistent with water flow.
The feature suggests that "vast flooding events, which are known to have occurred from beneath Mars’ surface throughout its geological history, still happen," the Muller, Murray and their colleagues write. "The presence of liquid water for thousands of millions of years, even beneath the surface, is a possible habitat in which primitive life may have developed, and might still be surviving now. Clearly this must now be considered as a prime site for future missions looking for life."
The researchers propose that the ice has been protected from sublimation by an overlying layer of volcanic ash.
"I think it's fairly plausible," Michael Carr, an expert on Martian water at the U.S. Geological Survey, told New Scientist. "We know where the water came from," said Carr, who was not involved in the work. "You can trace the valleys carved by water down to this area."
This layer of cold air, say the Levins, provides a form of insulation, trapping the water moisture below. Since the atmosphere is too cold to hold the water as vapor and the ground is warm enough to melt the ice, the water melts into a liquid. This liquid water, the Levins believe, remains on the Surface until the temperature of the atmosphere rises enough to allow the water to evaporate. In this way, they argue, the martian soil becomes briefly saturated with liquid water every day.
"The meteorological data fully confirm the presence of liquid water in the topsoil each morning," says Gilbert Levin. "The black-and-white as well as the color images show slick areas that may well be moist patches."
WASHINGTON -- Researchers using NASA's Mars Global Surveyor spacecraft announced Thursday that they found puzzling signs of water seeping into what appear to be young, freshly-cut gullies and gaps in the Martian surface.The startling discovery of recently-formed, weeping layers of rock and sediment has planetary experts scratching their heads.The wet spots show up in more than 120 locations on Mars and in the coldest places on the planet, said Michael Malin of Malin Space Science Systems in San Diego, California, which built the spacecraft's camera.
And that presents a "perplexing problem," he said, because logic says that Mars sub-zero temperatures and thin atmosphere should have kept those wet spots from ever forming.The wet spots, which turn up in 200 to 250 different images from the Global Surveyor spacecraft, "could be a few million years old but we cannot rule out that some of them are so recent as to have
formed yesterday," Malin said.
Rumors about what has been actually identified are about as fluid as liquid itself, from water-ice deposits, concentrations of iron, to Martian springs, and even Old Faithful-like geysers.
SPACE.com has learned that NASA has discovered evidence of water on the Red Planets surface. The finding, made bythe Mars Global Surveyor spacecraft, fuels hopes that there may be life onMars.Sources close to theagencys Mars program said the discovery involves evidence of seasonal deposits that could be associated with springs on the planets surface
NASA announces discovery of evidence of water on Mars
Off course there is frozen water in the poles and some isolated canyons.They now believe what before was thought to be erosion caused by water the cause is now lava or meteor impacts.
"I have also seen liquid water running from snow melting on dark rocks heated by sunlight in Antarctica, even though the air temperature was below -20 °C."
There are many places on Earth where liquid water and ice co-exist in sub-zero conditions, says Hoover. The most famous example is Lake Vostok, an expanse of water roughly the size of lake Ontario lying 4 km beneath the Antarctic ice sheet. The ice sheet acts as a blanket, shielding the lake from Mars-like temperatures at the surface.
Will explorers one day discover oases like Lake Vostok beneath icy terrain on Mars? No one knows. But instead of "Follow the Water," the mantra of future colonists on the red planet might well be "Follow the Salt."
A team of researchers from the University of Arkansas has measured water evaporation rates under Mars-like conditions, and their findings favor the presence of surface water on the planet. Water on the planet's surface makes the existence of past or present life on Mars a little more likely, according to the group.
Derek Sears, director of the Arkansas-Oklahoma Center for Space and Planetary Sciences, and his colleagues graduate student Shauntae Moore and technician Mikhail Kareev reported their initial findings at the fall 2003 meeting of the Division of Planetary Sciences of the AAS.
The researchers have brought on-line a large planetary environmental chamber in which temperature, pressure, atmosphere, sunlight and soil conditions can be reproduced. Sears and his colleagues use the chamber to investigate the persistence of water under a range of physical environments and to study its evaporation.
"These findings suggest that even under worst case scenarios, where wind is maximizing evaporation, evaporation rates on Mars are quite low," Sears said. This implies that surface water could indeed exist, or have existed recently, under the given conditions on Mars.
On Mars the globally-averaged surface pressure of the planet's atmosphere is only slightly less than 6.1 millibars.
"That's the average," says Haberle, "so some places will have pressures that are higher than 6.1 millibars and others will be lower. If we look at sites on Mars where the pressure is a bit higher, that's where water can theoretically exist as a liquid."