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TOPIC: Mars Water
Blobrana


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Martian Ocean
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Scientists have found new evidence to support the presence of large oceans on Mars in the past. Published in the June 14 issue of Nature, the research suggests that changes in Mars orientation with respect to its axis might be responsible for large variations in the topography of shoreline-like features on the planet. Scientists have studied these features for more than 30 years, and the current study presents a new, alternative explanation for how they formed.
Geophysicists have discovered that irregularities in proposed Martian shorelines might be explained by surface deformation from true polar wander. Through this phenomenon, Mars' spin axis and poles shifted by nearly 3,000 kilometres along the surface sometime within the past 2 or 3 billion years. Spinning planets bulge at their equator and solid surfaces deform differently than liquid sea surfaces. As a result, surface topography of the shorelines deformed as the planets rotation axis shifted.

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Blobrana


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RE: Mars Water
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A new analysis of pictures taken by the exploration rover Opportunity reveals what appear to be small ponds of liquid water on the surface of Mars.
The report identifies specific spots that appear to have contained liquid water two years ago, when Opportunity was exploring a crater called Endurance. It is a highly controversial claim, as many scientists believe that liquid water cannot exist on the surface of Mars today because of the planets thin atmosphere.
If confirmed, the existence of such ponds would significantly boost the odds that living organisms could survive on or near the surface of Mars, says physicist Ron Levin, the report's lead author, who works in advanced image processing at the aerospace company Lockheed Martin in Arizona.
Along with fellow Lockheed engineer Daniel Lyddy, Levin used images from the Jet Propulsion Laboratory's website. The resulting stereoscopic reconstructions, made from paired images from the Opportunity rover's twin cameras, show bluish features that look perfectly flat. The surfaces are so smooth that the computer could not find any surface details within those areas to match up between the two images.

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Blobrana


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Signs of recent liquid water on Mars may have instead been caused by mini-avalanches of dirt. In December, NASA released photos of Martian gullies that showed enigmatic tracks of material suddenly appearing in the last five years. Researchers interpreted the deposits as having possibly come from trickling water.
The problem with that theory is that such features can be reproduced in the lab by letting small particles slide away, says granular materials researcher Troy Shinbrot of Rutgers University.

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Blobrana


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Mars Clouds
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Planetary scientists have discovered the highest clouds above any planetary surface. They found them above Mars using the SPICAM instrument on board ESA's Mars Express spacecraft. The results are a new piece in the puzzle of how the Martian atmosphere works.

Until now, scientists had been aware only of the clouds that hug the Martian surface and lower reaches of the atmosphere. Thanks to data from the SPICAM Ultraviolet and Infrared Atmospheric Spectrometer onboard Mars Express, a fleeting layer of clouds have been discovered at an altitude between 80 and 100 kilometres. The clouds are most likely composed of carbon dioxide.
SPICAM made the discovery by observing distant stars just before they disappeared behind Mars. By looking at the effects on the starlight as it travelled through the Martian atmosphere, SPICAM built up a picture of the molecules at different altitudes. Each sweep through the atmosphere is called a profile.
The first hints of the new cloud layer came when certain profiles showed that the star dimmed noticeably when it was behind the 90–100 kilometre high atmospheric layer. Although this happened in only one percent of the profiles, by the time the team had collected 600 profiles, they were confident that the effect was real.


Credit NASA Pathfinder

They look similar to the mesospheric clouds, also known as noctilucent clouds, on Earth. These occur at 80 kilometres altitude above our planet, where the density of the atmosphere is similar to that of Mars’ at 35 kilometres. The newly discovered Martian clouds therefore occur in a much more rarefied atmospheric location.
At 90–100 kilometres above the Martian surface, the temperature is just –193° Celsius. This means that the clouds are unlikely to be made of water.

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RE: Mars Olivine
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New research asserts that subsurface reactions of olivine and water could produce enough methane to account for recent observations of the gas in the atmosphere, removing the need to invoke living microbes to do the job.

Olivine is one of the first minerals to crystallise out of molten rock. But at lower temperatures and in the presence of water, it breaks down quickly into other minerals.
Phil Christensen, a geologist at Arizona State University, and Victoria Hamilton of the University of Hawaii in Honolulu, US, used infrared images taken with NASA's Mars Odyssey spacecraft to show that the olivine-rich rocks on the flank of the volcano.
Syrtis Major cover a surface area of 113,000 square kilometres - about half the size of the UK.


That is nearly four times larger than the estimate made by NASA's Mars Global Surveyor (MGS) spacecraft. The difference has been attributed to Odyssey's ability to resolve details as small as 100 metres across, a 30-fold improvement over MGS. Christensen and Hamilton’s study is published in the journal Geology .
The rocks, at latitude of 20° north of the planet's equator, appear to have formed through successive lava eruptions about 3 billion years ago.
"To keep olivine around so long suggests this area of Mars may not have seen a lot of water or a warm climate," - Victoria Hamilton.

That finding differs markedly from the recent discoveries made by the Mars rovers of minerals that form in the presence of water. But Christensen says such discoveries represent rare flooding events lasting for weeks or months and that for most of the planet's 4.5 billion-year history, any water has been locked in ice.
"I am not a proponent of the idea that Mars had oceans in the past," -Phil Christensen. He says mineral mapping from orbit reveals most of the planet is covered in volcanic rocks, which "shows most of Mars hasn't seen much water". Scientists have failed to find minerals such as carbonates and clays that form in oceans on Earth.

"I'm moving in the direction of 'cold and dry' more and more…But there are other scientists headed in the other direction, thinking Mars was warmer and wetter. It is an ongoing discussion. " - Victoria Hamilton.
The discovery of more olivine on the surface of Mars also supports the argument that underground reserves of the mineral could produce methane, says geologist Mukul Sharma of Dartmouth College in Hanover, New Hampshire, US. He and colleague Chris Oze detail their proposal in the journal Geophysical Research Letters (vol 32, L10203).
Olivine tends to sink when it crystallises from magma, which "implies at some depth there has to be a lot more olivine than you see on the surface, " - Mukul Sharma.

The team says there is enough olivine in the top 10 kilometres of the crust to explain the recent detections of methane in Mars's atmosphere - if there are stores of liquid water underground, as many scientists suspect.
Water reacts with a common, iron-rich form of olivine by producing hydrogen gas, which then combines with carbon dioxide to produce methane. The gas could then leak to the surface through gullies.

"The easiest way to produce all the methane people have observed is by the reaction of olivine with water," - Mukul Sharma.
Other researchers have proposed that microbes might be a continuous source of the gas, which is easily destroyed by sunlight in the atmosphere.



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Blobrana


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RE: Nili Fossae
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Mineralogy surrounding the Nili Fossae, Mars, as seen in a mosaic of infrared images from NASA's Mars Odyssey Thermal Emission Imaging System.


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Bands 5 (9.35 µm, 1070 cm-1), 7 (11.04 µm, 906 cm-1), and 9 (12.57 µm, 796 cm-1) are displayed in blue, green, and red, respectively. Within this largely basaltic region, olivine-rich exposures stand out as magenta to purple-blue in colour.


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Blobrana


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Posts: 131433
Date:
Mars Water
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Martian surface morphology records a complex, changeable geologic history that suggests the planet may have been more hospitable to life during its early history. While the present atmosphere is predominantly CO2 and only about 1% of the density of Earth's atmosphere, but robotic satellites and rovers have returned new evidence of a warmer and wetter climate more than 3.5 billion years ago, when conditions may have been more favourable for life.
For example, most of the valleys and channels cutting the surface are thought to have been created by flowing water, something that is nearly impossible to sustain under present cold conditions (the average temperature is -23°C).
Geologists at the Smithsonian National Air and Space Museum's Centre for Earth and Planetary Studies, working with colleagues at the University of Virginia, have discovered 21 river channels in the dry Martian valleys, which provide new clues to this ancient climate.
The researchers have determined that Martian rivers were about the same size as their counterparts on Earth, suggesting similar amounts of runoff from thunderstorms or rapid snowmelt.
The findings will appear in the June 2005 issue of the journal Geology.



Until the discovery of channels, scientists could not determine the amount of water that had flowed through these valleys.
"We have thought for some time that it likely rained or snowed on early Mars, but until we found the river channels we had no idea whether we were dealing with drizzle or storms." - Ross Irwin, museum geologist, and lead author.

Co-authors Robert Craddock, another National Air and Space Museum geologist, and Alan Howard of the University of Virginia made a detailed "Case for Rainfall on a Warm, Wet Early Mars" in a 2002 paper.

Larger, periodic floods carve wider river channels, so by measuring the width of a channel, geologists can estimate the size of the flood that carved it.
To explain the width of the Martian channels, some watersheds likely received two centimetres or more of rain per day during storms, or more than 25cm of melted snow on particularly warm days.
Larger watersheds gave rise to larger river channels, as they do on Earth. Even using a conservative method to estimate the amount of water discharged through the rivers, the Martian rivers still matched their terrestrial counterparts in terms of the volume of water per second during these ancient episodes of flow.

Previously, only eight river channels had been found in Martian valleys, two of these by Irwin and Howard in 2002. The new discoveries were made using the THEMIS camera on the Mars Odyssey spacecraft that is currently in orbit around Mars.

You can explore the run-offs yourself:
To boldly Go link: (JavaScript Application)
Use the buttons/mouse to explore/zoom in anywhere on the interactive map of the surface of Mars.

During the 3.5 billion years since water flowed in these channels, the valley floors have become partly filled by wind-blown sand and debris from meteorite impacts, so the channels are exposed along only part of their floors.
The Martian river channels do not appear to have been active nearly as long as terrestrial rivers have however.
"If it rained this hard every day throughout the many millions of years that runoff occurred, Mars would be far more heavily eroded than it is. It seems more likely that Mars was wet at times with drier intervals in between." - Ross Irwin.

Mars may have always been a desert, but like some deserts here on Earth, water appears to have flowed abundantly at least part of the time.
The Centre for Earth and Planetary Studies is the scientific research unit within the Collections and Research Department of the Smithsonian Institution's National Air and Space Museum. The Centre’s scientists perform original research and outreach activities on topics covering planetary science, terrestrial geophysics and the remote sensing of environmental change.
http://www.nasm.si.edu/research/ceps/research/mars/mars.cfm (old website)



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