Delta-like Fan on Mars Suggest Ancient Rivers were Persistent Newly seen details in a fan-shaped apron of debris on Mars may help settle a decades-long debate about whether the planet had long-lasting rivers instead of just brief, intense floods. November 13, 2003
MARS-LIKE ATACAMA DESERT COULD EXPLAIN VIKING 'NO LIFE' RESULTS
A team of scientists from NASA, the Universidad Nacional Autonoma de
Mexico, Louisiana State University and several other research
organizations has discovered clues from one of Earth's driest deserts
about the limits of life on Earth, and why past missions to Mars may
have failed to detect life.
More from NASA Ames Research Center Nov. 7, 2003
November 3, 2003
Sand Ripples Taller On Mars
In addition to the
biggest canyon and biggest volcano in the solar system, Mars has now been
found to have sand ripples twice as tall as they would be on Earth.
Initial measurements of some of the Red Planet's dunes and ripples using
stereo-images from the Mars Orbiter Camera onboard the Mars Global Surveyor
have revealed ripple features reaching almost 20 feet high and dunes
towering at 300 feet.
The Geological Society of America News Release
The Mars Global Surveyor Mars Orbiter Camera Image Gallery contains more than 134,000 Images! It has all of the pictures of Mars acquired by NASA's Mars Global Surveyor (MGS) orbiter through February 2003.
Mars Orbital Camera (MOC)is operated daily at Malin Space Science Systems (MSSS). MOC consists of three cameras: A narrow angle system that provides grayscale high resolution views of the planet's surface (typically, 1.5 to 12 meters/pixel), and red and blue wide angle cameras that provide daily global weather monitoring, context images to determine where the narrow angle views were actually acquired, and regional coverage to monitor variable surface features such as polar frost and wind streaks. Most of the high resolution images are obtained by careful planning and inspection of predicted MGS orbits by Mars scientists working at and/or visiting MSSS. The company is also responsible for archiving the data once they are received on Earth. To visit the Gallery, click here.
Northwest Hellas Planitia presents an array of strange-looking surfaces. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows an example near 39.3°S, 306.7°W. The scene is illuminated by sunlight from the upper left. Some of the banding apparent in this image may be related to layering, but the overall cause for the patterns remains elusive. Hellas Basin is a difficult place to obtain MOC high resolution images, because for most of the year it is cloudy. The clouds clear up and imaging opportunities are spectacular in southern autumn, the time of year that this image was obtained. This picture covers an area 3 km (1.9 mi) wide. - credit: Malin Space Science Systems
The following new images taken by the Mars Orbiter Camera (MOC) on the Mars Global Surveyor spacecraft are now available:
A Traveller's Guide to Mars: The Mysterious Landscapes of the Red Planetby William K. Hartmann 
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All of the THEMIS images are archived here
NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
Research by a University at Buffalo planetary geologist suggests that generally accepted estimates about the geologic age of surfaces on Mars -- which influence theories about its history and whether or not it once sustained life -- could be way off.
Funded by the National Aeronautics and Space Administration, the research eventually could overturn principles about the relative ages of different areas on the Red Planet that have not been questioned for nearly 20 years.
The Universe in a Nutshellby Stephen William Hawking The Universe in a Nutshell attempts to address the relative difficulty of Hawking's first foray into popular science, A Brief History of Time. While this sold in its millions, few readers got past the first few chapters. Helpfully, this new work is full of beautifully prepared colour illustrations |
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The findings also could cause scientists to reconsider the use of a critical tool -- counting impact craters created by meterorites -- that geologists use to estimate the age of planets they cannot visit in person.
"This has the potential to change everything we thought we knew about the age of different surfaces on Mars," said Tracy Gregg, Ph.D., assistant professor of geology at UB and chair of the Planetary Geology Division of the Geological Society of America. David Crown, Ph.D., of the Planetary Science Institute, is Gregg's co-investigator on the grant.
Gregg's research concerns an area on Mars called Hesperia Planum, which has been used since the 1980s to define the Hesperian epoch, the second of the planet's three geologic time periods.
But in the past several years, recent analyses of images obtained from the Mars Orbiter Laser Altimeter, (MOLA), the Mars Orbiter Camera (MOC) and other instruments have led to new estimates for the duration of the Hesperian epoch, ranging from just 300,000 years to 1-2 billion years, Gregg explained.
While other planetary geologists now are attempting to reconcile these two models, she said, her focus is on trying to figure out which surfaces on Mars originated in the Hesperian epoch, research that, in turn, probably will help to further define the duration of the Hesperian epoch.
"For almost 20 years, Hesperia Planum has served as the basic time marker on Mars," said Gregg.
"When we want to identify how old rocks are without the benefit of samples, we count impact craters, the big holes in planetary surfaces that are made by meteorites that crash into them," explained Gregg. "The more impact craters there are on a surface, the older it is."
But during the course of Gregg's research reviewing images of Tyrrhena Patera, a volcano located in the middle of Hesperia Planum, she began finding deposits from not one Martian geologic epoch but from several.
Gregg made her findings using images obtained from the Viking Orbiter, the Mars Global Surveyor, the MOLA and the MOC. She also will be using data NASA is making available from THEMIS, the Thermal Mapping Infrared Spectrometer, which measures surface temperatures on Mars.
"Hesperia Planum is not one age. Its surface actually is a combination of materials that are very old, materials that are very young and some that are in between," she said, "and the volcanoes there are the reason why."
Gregg recently has demonstrated that two volcanoes in western Hesperia Planum were active during a much longer period than previously was understood and that the products of the eruptions traveled much further, signaling a greater intensity of volcanic activity than originally was thought.
Her findings, she said, are similar to ones made about 20 years ago on Earth, when geologists discovered that Yellowstone National Park in Wyoming was the center crater of an enormous volcano and that its deposits stretched as far as the state of Illinois.
Those findings, she said, changed fundamentally the understanding of volcanic activity on Earth.
In a similar vein, she said, the new observations about the great distances traveled by deposits of Martian volcanoes and their influence on the age of surfaces may cause a similar reconsideration of understanding of the history of Mars.
"I think that we are about to discover that Hesperia Planum, this surface that has acted as a basic time marker for Mars, has a very ifferent age than we thought," she said. "If it turns out it's much older than we thought, then it means that the system shut down a lot earlier and the chances of finding active living organisms on Mars are much slimmer.
"If, on the other hand, it turns out to be much younger, then it means Mars still may be volcanologically active, and if it is, that increases the possibility of extant life on Mars."
Nov. 7, 2003
NASA Ames Research Center, Moffett Field, Calif.
PRESS RELEASE: 03-87AR
A team of scientists from NASA, the Universidad Nacional Autonoma de Mexico, Louisiana State University and several other research organizations has discovered clues from one of Earth's driest deserts about the limits of life on Earth, and why past missions to Mars may have failed to detect life.
The results were published this week in Science magazine in an article entitled "Mars-like Soils in the Atacama Desert, Chile, and the Dry Limit of Microbial Life."
NASA's Viking missions to Mars in the 1970s showed the martian soil to be disappointingly lifeless and depleted in organic materials, the chemical precursors necessary for life. Last year, in the driest part of Chile's Atacama Desert, the research team conducted microbe-hunting experiments similar to Viking's, and no evidence of life was found. The scientists called the finding "highly unusual" in an environment exposed to the atmosphere.
"In the driest part of the Atacama, we found that, if Viking had landed there instead of on Mars and done exactly the same experiments, we would also have been shut out," said Dr. Chris McKay, the expedition's principal investigator, who is based at NASA Ames Research Center, Moffett Field, Calif. "The Atacama appears to be the only place on Earth Viking would have found nothing."
During field studies, the team analyzed Atacama's depleted Mars-like soils and found organic materials at such low levels and released at such high temperatures that Viking would not have been able to detect them, said McKay, who noted that the team did discover a non-biological oxidative substance that appears to have reacted with the organics -- results that mimicked Viking's results.
"The Atacama is the only place on Earth that I've taken soil samples to grow microorganisms back at the lab and nothing whatsoever grew," said Dr. Fred A. Rainey, a co-author from Louisiana State University, who studies microorganisms in extreme environments.
According to the researchers, the Atacama site they studied could serve as a valuable testbed for developing instruments and experiments that are better tailored to finding microbial life on Mars than the current generation. "We think Atacama's lifeless zone is a great resource to develop portable and self-contained instruments that are especially designed for taking and analyzing samples of the martian soil," McKay said.
More sophisticated instruments on future sample-return Mars missions are a necessity if scientists are to avoid contaminating future martian samples, McKay noted. "We're still doing the first steps of instrument development for Mars." Recently, researchers have developed a method to extract DNA from soil without humans getting involved in processing the data, which is "a step in the right direction," according to McKay.
The reason Chile's Atacama Desert is so dry and virtually sterile, researchers say, is because it is blocked from moisture on both sides by the Andes mountains and by coastal mountains. At 3,000 feet, the Atacama is 15 million years old and 50 times more arid than California's Death Valley. The scientists studied the driest part of the Atacama, an area called the 'double rain shadow.' During the past four years, the team's sensor station has recorded only one rainfall, which shed a paltry 1/10 of an inch of moisture. McKay hypothesizes that it rains in the arid core of the Atacama on average of only once every 10 years.
The Atacama research was funded by NASA's Astrobiology Science and Technology for Exploring Planets program, by Louisiana State University, the National Science Foundation and by several other organizations.
The article was also authored by Dr. Rafael Navarro-Gonzalez, Dr. Paola Molina and Dr .Jose de la Rosa from the Universidad Nacional Autonoma de Mexico, Mexico City, MX; Danielle Bagaley, Becky Hollen and Alanna Small, Louisiana State University, Baton Rouge, LA.; Dr. Richard Quinn, the SETI Institute, Mountain View, Calif.; Dr. Frank Grunthaner, NASA Jet Propulsion Laboratory, Pasadena, Calif.; Dr. Luis Caceres, Instituto del Desierto y Departameno de Ingenieria, Quimica; and Dr. Benito Gomez-Silva, Instituto del Desierto y unidad de Bioquimica, Universidad de Antofagasta, Antofagasta, Chile.
Mars is kind of like Texas: things are just bigger there. In addition to the biggest canyon and biggest volcano in the solar system, Mars has now been found to have sand ripples twice as tall as they would be on Earth.
Initial measurements of some of the Red Planet's dunes and ripples using stereo-images from the Mars Orbiter Camera onboard the Mars Global Surveyor have revealed ripple features reaching almost 20 feet high and dunes towering at 300 feet.
One way to imagine the taller dimension of ripples on Mars is to visualize sand ripples on Earth, then stretch out the vertical dimension to double height, without changing the horizontal dimension.
"They do seem higher in relation to ripples on Earth," said Kevin Williams of the Smithsonian National Air and Space Museum. Williams will be presenting this latest insight into the otherworldly scale of Marscapes on Monday, Nov. 3 at the annual meeting of the Geological Society of America in Seattle, WA.
Ripples are common on Mars and usually found in low-lying areas and inside craters, says Williams. On Earth they tend to form in long parallel lines from sand grains being pushed by water or air at right angles to the ripple lines. Dunes, on the other hand, are formed when grains of sand actually get airborne and "saltate" (a word based on the Latin verb "to jump"). That leads to cusp-shaped, star-shaped, and other dune arrangements that allow materials to pile sand much higher.
How exactly Martian dunes and ripples form is still unknown, says Williams, since the images from space give us no clues to the grain sizes or whether they are migrating or moving in any way. Though there are Viking spacecraft images from almost 30 years ago to compare with, the images do not have the resolution to confirm whether ripples have moved much in that time. For now, the dimensions of ripple-forms on Mars are the only indications of whether they are large ripples or small dunes. Williams' results came about from the advantageous combination of image parameters to get the first height measurements of these ripple-like features at the limit of image resolution.
According to Williams, it's likely the doubled heights of Mars ripples relative to their spacing is made possible by the same thing that makes Mars' volcanoes so tall: lower gravity. With about one-third the gravity of Earth, sand, silt, and dust can theoretically stack up higher before gravity causes a slope failure.
However, other differences could play roles in making these large piles of sand as well. "It could also be from different wind speeds, air densities or other factors," said Williams. Mars has a perennially subfreezing, very thin atmosphere in which global dust storms have been known to obscure the surface from view.
The study of Mars dunes and ripples has been underway since Viking spacecraft images of Mars first revealed such features in the late 1970s and early 1980s, says Williams. The primary difficulty of the work continues to be in discerning the close-up details, like the exact heights of features and grain sizes. As with dunes and ripples on Earth, these wind-blown features could reveal a lot about local and regional weather and wind currents - if more was known about ripple and dune building under the very un-Earthlike conditions of Mars.
So far the only close-encounters humans have ever had with Martian dunes were with the Viking Landers and the Pathfinder mission, which sent the Sojourner rover trundling among Martian boulders. "There were some small dunes in the area of Pathfinder," Williams said.
There are also likely to be ripples or small dunes within range of the far more mobile Mars Exploration Rovers now enroute to the Red Planet, Williams said. The Mars Exploration Rovers, Spirit and Opportunity, are larger and will be able to travel much further than Sojourner, making it more likely they will be taking a closer look at ripples as well as other geological features of Mars.
More informationNewly seen details in a fan-shaped apron of debris on Mars may help settle a decades-long debate about whether the planet had long-lasting rivers instead of just brief, intense floods.
Pictures from NASA's Mars Global Surveyor orbiter show eroded ancient
deposits of transported sediment long since hardened into
interweaving, curved ridges of layered rock. Scientists interpret some
of the curves as traces of ancient meanders made in a sedimentary fan
as flowing water changed its course over time.
"Meanders are key, unequivocal evidence that some valleys on early Mars held persistent flows of water over considerable periods of time," said Dr. Michael Malin of Malin Space Science Systems, San Diego, which supplied and operates the spacecraft's Mars Orbiter Camera.
"The shape of the fan and the pattern of inverted channels in it suggest it may have been a real delta, a deposit made where a river enters a body of water," he said. "If so, it would be the strongest indicator yet Mars once had lakes."
Malin and Dr. Ken Edgett, also of Malin Space Science Systems, have published pictures and analysis of the landform in today's online edition of Science Express. The images with captions are available online from the Mars Orbiter Camera team, and from NASA's Jet Propulsion Laboratory, Pasadena, Calif.
The fan covers an area about 13 kilometers (8 miles) long and 11 kilometers (7 miles) wide in an unnamed southern hemisphere crater downslope from a large network of channels that apparently drained into it billions of years ago.
"This latest discovery by the intrepid Mars Global Surveyor is our first definitive evidence of persistent surface water", commented Dr. Jim Garvin, NASA's Lead Scientist for Mars Exploration, NASA Headquarters, Washington, D.C. "It reaffirms we are on the right pathway for searching the record of martian landscapes and eventually rocks for the record of habitats. Such localities may serve as key landing sites for future missions, such as the Mars Science Laboratory in 2009", continued Garvin. "These astounding findings suggest that "following the water" with Mars Global Surveyor, Mars Odyssey, and soon with the Mars Exploration Rovers, is a powerful approach that will ultimately allow us to understand the history of habitats on the red planet".
No liquid water has been detected on Mars, although one of the previous major discoveries from Mars Global Surveyor pictures suggests that some gullies have been cut in geologically recent times by the flow of ephemeral liquid water. Another NASA orbiter, Mars Odyssey, has discovered extensive deposits of near-surface ice at high latitudes. Mars' atmosphere is now so thin that, over most of the planet, any liquid water at the surface would rapidly evaporate or freeze, so evidence of persistent surface water in the past is also evidence for a more clement past climate.
Malin and Edgett estimate that the volume of material in the delta-like fan is about one-fourth the volume of what was removed by the cutting of the upstream channels. Their analysis draws on information from Mars Global Surveyor's laser altimeter and from cameras on Mars Odyssey and NASA's Viking Orbiter, as well as images from the Mars Orbiter Camera.
"Because the debris in this fan is now cemented, it shows that some sedimentary rocks on Mars were deposited by water," Edgett said. "This has been suspected, but never so clearly demonstrated before."
The camera on Mars Global Surveyor has returned more than 155,000 pictures since the spacecraft began orbiting Mars on Sept. 12, 1997. Still, its high-resolution images cover only about three percent of the planet's surface.
JPL, a division of the California Institute of Technology, Pasadena, manages Mars Global Surveyor for NASA's Office of Space Science in Washington. JPL's industrial partner is Lockheed Martin Space Systems, Denver, which developed and operates the spacecraft. Malin Space Science Systems and the California Institute of Technology built the Mars Orbiter Camera. Malin Space Science Systems operates the camera from facilities in San Diego.
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