NASA - Mars Reconnaissance Orbiter (MRO) patch.
Sept. 28, 2015
Image above: These dark, narrow, 100 meter-long streaks called recurring slope lineae flowing downhill on Mars are inferred to have been formed by contemporary flowing water. Recently, planetary scientists detected hydrated salts on these slopes at Hale crater, corroborating their original hypothesis that the streaks are indeed formed by liquid water. The blue color seen upslope of the dark streaks are thought not to be related to their formation, but instead are from the presence of the mineral pyroxene. The image is produced by draping an orthorectified (Infrared-Red-Blue/Green(IRB)) false color image (ESP_030570_1440) on a Digital Terrain Model (DTM) of the same site produced by High Resolution Imaging Science Experiment (University of Arizona). Vertical exaggeration is 1.5. Image Credits: NASA/JPL/University of Arizona.
New findings from NASA's Mars Reconnaissance Orbiter (MRO) provide the strongest evidence yet that liquid water flows intermittently on present-day Mars.
Using an imaging spectrometer on MRO, researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet. These darkish streaks appear to ebb and flow over time. They darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons. They appear in several locations on Mars when temperatures are above minus 10 degrees Fahrenheit (minus 23 Celsius), and disappear at colder times.
“Our quest on Mars has been to ‘follow the water,’ in our search for life in the universe, and now we have convincing science that validates what we’ve long suspected,” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate in Washington. “This is a significant development, as it appears to confirm that water -- albeit briny -- is flowing today on the surface of Mars.”
These downhill flows, known as recurring slope lineae (RSL), often have been described as possibly related to liquid water. The new findings of hydrated salts on the slopes point to what that relationship may be to these dark features. The hydrated salts would lower the freezing point of a liquid brine, just as salt on roads here on Earth causes ice and snow to melt more rapidly. Scientists say it’s likely a shallow subsurface flow, with enough water wicking to the surface to explain the darkening.
Image above: Dark narrow streaks called recurring slope lineae emanating out of the walls of Garni crater on Mars. The dark streaks here are up to few hundred meters in length. They are hypothesized to be formed by flow of briny liquid water on Mars. The image is produced by draping an orthorectified (RED) image (ESP_031059_1685) on a Digital Terrain Model (DTM) of the same site produced by High Resolution Imaging Science Experiment (University of Arizona). Vertical exaggeration is 1.5. Image Credits: NASA/JPL/University of Arizona.
"We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks," said Lujendra Ojha of the Georgia Institute of Technology (Georgia Tech) in Atlanta, lead author of a report on these findings published Sept. 28 by Nature Geoscience.
Ojha first noticed these puzzling features as a University of Arizona undergraduate student in 2010, using images from the MRO's High Resolution Imaging Science Experiment (HiRISE). HiRISE observations now have documented RSL at dozens of sites on Mars. The new study pairs HiRISE observations with mineral mapping by MRO’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).
The spectrometer observations show signatures of hydrated salts at multiple RSL locations, but only when the dark features were relatively wide. When the researchers looked at the same locations and RSL weren't as extensive, they detected no hydrated salt.
Ojha and his co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate. Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as minus 94 degrees Fahrenheit (minus 70 Celsius). On Earth, naturally produced perchlorates are concentrated in deserts, and some types of perchlorates can be used as rocket propellant.
Perchlorates have previously been seen on Mars. NASA's Phoenix lander and Curiosity rover both found them in the planet's soil, and some scientists believe that the Viking missions in the 1970s measured signatures of these salts. However, this study of RSL detected perchlorates, now in hydrated form, in different areas than those explored by the landers. This also is the first time perchlorates have been identified from orbit.
MRO has been examining Mars since 2006 with its six science instruments.
"The ability of MRO to observe for multiple Mars years with a payload able to see the fine detail of these features has enabled findings such as these: first identifying the puzzling seasonal streaks and now making a big step towards explaining what they are," said Rich Zurek, MRO project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.
Animation of Site of Seasonal Flows in Hale Crater, Mars
Video above: This animation simulates a fly-around look at one of the places on Mars where dark streaks advance down slopes during warm seasons, possibly involving liquid water. This site is within Hale Crater. The streaks are roughly the length of a football field.
For Ojha, the new findings are more proof that the mysterious lines he
first saw darkening Martian slopes five years ago are, indeed,
present-day water.
"When most people talk about water on Mars,
they're usually talking about ancient water or frozen water," he said.
"Now we know there’s more to the story. This is the first spectral
detection that unambiguously supports our liquid water-formation
hypotheses for RSL."
The discovery is the latest of many breakthroughs by NASA’s Mars missions.
“It
took multiple spacecraft over several years to solve this mystery, and
now we know there is liquid water on the surface of this cold, desert
planet,” said Michael Meyer, lead scientist for NASA’s Mars Exploration
Program at the agency’s headquarters in Washington. “It seems that the
more we study Mars, the more we learn how life could be supported and
where there are resources to support life in the future.”
There are eight co-authors of the Nature Geoscience paper, including
Mary Beth Wilhelm at NASA’s Ames Research Center in Moffett Field,
California and Georgia Tech; CRISM Principal Investigator Scott Murchie
of the Johns Hopkins University Applied Physics Laboratory in Laurel,
Maryland; and HiRISE Principal Investigator Alfred McEwen of the
University of Arizona Lunar and Planetary Laboratory in Tucson, Arizona.
Others are at Georgia Tech, the Southwest Research Institute in
Boulder, Colorado, and Laboratoire de Planétologie et Géodynamique in
Nantes, France.
Recurring "Lineae" on Slopes at Horowitz Crater
Image above: The dark, narrow streaks flowing downhill on Mars at sites such as this portion of Horowitz Crater are inferred to be formed by seasonal flow of water on modern-day Mars. The streaks are roughly the length of a football field. Image Credits: NASA/JPL-Caltech/Univ. of Arizona.
The imaging and topographical information in this processed view come from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.
These dark features on the slopes are called "recurring slope lineae" or RSL. Planetary scientists using observations with the Compact Reconnaissance Imaging Spectrometer on the same orbiter detected hydrated salts on these slopes at Horowitz Crater, corroborating the hypothesis that the streaks are formed by briny liquid water.
The image was produced by first creating a 3-D computer model (a digital terrain map) of the area based on stereo information from two HiRISE observations, and then draping an image over the land-shape model. The vertical dimension is exaggerated by a factor of 1.5 compared to horizontal dimensions. The draped image is a red waveband (monochrome) product from HiRISE observation PSP_005787_1475, taken on Oct. 21, 2007, at 32 degrees south latitude, 141 degrees east longitude. Other image products from this observation are at
http://www.uahirise.org/PSP_005787_1475.
Mars Reconnaissance Orbiter (MRO). Image Credit: NASA
The University of Arizona, Tucson, operates HiRISE, which was built by
Ball Aerospace & Technologies Corp., Boulder, Colorado. NASA's Jet
Propulsion Laboratory, a division of the California Institute of
Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project
and Mars Science Laboratory Project for NASA's Science Mission
Directorate, Washington.
The agency’s Jet Propulsion Laboratory (JPL) in Pasadena, California manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington. Lockheed Martin built the orbiter and collaborates with JPL to operate it.
More information about NASA's journey to Mars is available online at:
https://www.nasa.gov/topics/journeytomarsFor more information about the Mars Reconnaissance Orbiter, visit:
http://www.nasa.gov/mroImages (mentioned), Video, Text, Credits: NASA/Dwayne Brown/Laurie Cantillo/JPL/Guy Webster/Gina Anderson.
Best regards, Orbiter.ch
