Mars Orbiter

Test for Damp Ground at Mars Streaks Finds None

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Blue dots on this map indicate sites of recurring slope lineae (RSL) in part of the Valles Marineris canyon network on Mars. RSL are seasonal dark streaks that may be indicators of liquid water. The area mapped here has the highest density of known RSL on Mars. Image Credit: NASA/JPL-Caltech/Univ. of Arizona



Seasonal dark streaks on Mars that have become one of the hottest topics in interplanetary research don’t hold much water, according to the latest findings from a NASA spacecraft orbiting Mars.

The new results from NASA’s Mars Odyssey mission rely on ground temperature, measured by infrared imaging using the spacecraft’s Thermal Emission Imaging System (THEMIS). They do not contradict last year’s identification of hydrated salt at these flows, which since their 2011 discovery have been regarded as possible markers for the presence of liquid water on modern Mars. However, the temperature measurements now identify an upper limit on how much water is present at these darkened streaks: about as much as in the driest desert sands on Earth.

When water is present in the spaces between particles of soil or grains of sand, it affects how quickly a patch of ground heats up during the day and cools off at night.

“We used a very sensitive technique to quantify the amount of water associated with these features,” said Christopher Edwards of Northern Arizona University, Flagstaff. “The results are consistent with no moisture at all and set an upper limit at three percent water.”

The features, called recurring slope lineae or RSL, have been identified at dozens of sites on Mars. A darkening of the ground extends downhill in fingerlike flows during spring or summer, fades away in fall and winter, then repeats the pattern in another year at the same location. The process that causes the streaks to appear is still a puzzle.

“Some type of water-related activity at the uphill end still might be a factor in triggering RSL, but the darkness of the ground is not associated with large amounts of water, either liquid or frozen,” Edwards said. “Totally dry mechanisms for explaining RSL should not be ruled out.”

He and Sylvain Piqueux of NASA’s Jet Propulsion Laboratory, Pasadena, California, analyzed several years of THEMIS infrared observations of a crater-wall region within the large Valles Marineris canyon system on Mars. Numerous RSL features sit close together in some parts of the study region. Edwards and Piqueux compared nighttime temperatures of patches of ground averaging about 44 percent RSL features, in the area, to temperatures of nearby slopes with no RSL. They found no detectable difference, even during seasons when RSL were actively growing.

The report of these findings by Edwards and Piqueux has been accepted by the peer-reviewed Geophysical Research Letters and is available online.

There is some margin of error in assessing ground temperatures with the multiple THEMIS observations used in this study, enough to leave the possibility that the RSL sites differed undetectably from non-RSL sites by as much as 1.8 degrees Fahrenheit (1 Celsius degree). The researchers used that largest possible difference to calculate the maximum possible amount of water — either liquid or frozen — in the surface material.

How deeply moisture reaches beneath the surface, as well as the amount of water present right at the surface, affects how quickly the surface loses heat. The new study calculates that if RSL have only a wafer-thin layer of water-containing soil, that layer contains no more than about an ounce of water per two pounds of soil (3 grams water per kilogram of soil). That is about the same concentration of water as in the surface material of the Atacama Desert and Antarctic Dry Valleys, the driest places on Earth. If the water-containing layer at RSL is thicker, the amount of water per pound or kilogram of soil would need to be even less, to stay consistent with the temperature measurements.

Research published last year identified hydrated salts in the surface composition of RSL sites, with an increase during the season when streaks are active. Hydrated salts hold water molecules affecting the crystalline structure of the salt.

“Our findings are consistent with the presence of hydrated salts, because you can have hydrated salt without having enough for the water to start filling pore spaces between particles,” Edwards said. “Salts can become hydrated by pulling water vapor from the atmosphere, with no need for an underground source of the water.”

“Through additional data and studies, we are learning more about these puzzling seasonal features — narrowing the range of possible explanations,” said Michael Meyer. “It just shows us that we still have much to learn about Mars and its potential as a habitat for life.”

The new study touches on additional factors that add to understanding of RSL.

— If RSL were seasonal flows of briny water followed by evaporation, annual buildup of crust-forming salt should affect temperature properties. So the lack of a temperature difference between RSL and non-RSL sites is evidence against evaporating brines.

— Lack of a temperature difference is also evidence against RSL being cascades of dry material with different thermal properties than the pre-existing slope material, such as would be the case with annual avalanching of powdery dust that accumulates from dusty air.

Arizona State University, Tempe, provided and operates the THEMIS camera, which records observations in both infrared and visible-light wavelengths. JPL, a division of Caltech, manages the Mars Odyssey project for NASA. Lockheed Martin Space Systems, Denver, built the orbiter and collaborates with JPL to operate it.

PRESS RELEASE: NASA Seeks Industry Ideas for an Advanced Mars Satellite

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April 21, 2016
RELEASE 16-046
NASA Seeks Industry Ideas for an Advanced Mars Satellite

NASA is soliciting ideas from U.S. industry for designs of a Mars orbiter for potential launch in the 2020s. The satellite would provide advanced communications and imaging, as well as robotic science exploration, in support of NASA’s Journey to Mars.

The orbiter would substantially increase bandwidth communications and maintain high-resolution imaging capability. It also may use experimental cutting-edge technologies, such as high-power solar electric propulsion or an optical communications package, which could greatly improve transmission speed and capacity over radio frequency systems.

Under the direction of NASA’s Mars Exploration Program, the agency’s Jet Propulsion Laboratory (JPL) in Pasadena, California, is conducting pre-formulation planning for this possible orbiter mission. Pre-formulation plans include the procurement of industry studies for a solar-powered orbiting spacecraft. This effort seeks to take advantage of industry capabilities to improve deep space, solar electric propulsion-enabled orbiters to accommodate scientific instruments, demonstrate capability for rendezvous and capture, and advance telecommunications capabilities. 

“Our success in exploring Mars, to unravel the mysteries of the Red Planet, depends on having high bandwidth communication with Earth and overhead imaging,” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate in Washington. “Currently, we depend on our orbiting science missions to perform dual service in making measurements and acting as communication relays, but we can’t depend on them to last forever. This new orbiter will use cutting-edge technology to revitalize our ability to continue to explore Mars and support transformative science, including a potential sample return mission in the future.” 

JPL plans to award concept study subcontracts of $400,000 per subcontract in June. The concept studies for the spacecraft will be completed over a four-month period. 

In response to an earlier request from NASA, the Mars Exploration Program formed an analysis group that proposed, in a 2015 report, possible science objectives for a Mars orbiter capable of replenishing and advancing the telecommunications and reconnaissance resources available at Mars. 

NASA is studying how to implement this mission concept in concert with its international partners to the greatest extent possible. Historically, there have been significant international contributions to NASA Mars missions that include the Curiosity rover, Mars Reconnaissance Orbiter spacecraft and the Mars Atmosphere and Volatile Evolution Mission orbiter, both currently orbiting the Red Planet. The agency will seek such partnerships for this potential future orbiter mission, as well. 

NASA is on an ambitious journey to Mars that includes sending humans to the Red Planet, and that work remains on track. Robotic spacecraft are leading the way for the Mars Exploration Program, with current missions, in addition to the planned launch of the Insight lander in 2018, and the design and build of the Mars 2020 rover. 

To view the Mars orbiter solicitation/Federal Business Opportunities announcement, visit:


Scars on Mars from 2012 Rover Landing Fade — Usually

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This sequence of images shows a blast zone where the sky crane from NASA’s Curiosity rover mission hit the ground after setting the rover down in August 2012, and how that dark scar’s appearance changed over the subsequent 30 months. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

A series of observations from Mars orbit show how dark blast zones that were created during the August 2012 landing of NASA’s Curiosity rover have faded inconsistently.

The High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter made the observations on multiple dates from landing to last month. After fading for about two years, the pace of change slowed and some of the scars may have even darkened again.

The images track changes in blast zones at four locations caused by different pieces of Curiosity hardware, such as the heat shield and the descent stage. The four series, each with images from five to seven different dates since landing, are available online at:

“Spacecraft like Curiosity create these dark blast zone patterns where bright dust is blown away by the landing,” said Ingrid Daubar, a HiRISE team scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California, who has used similar blast zones to find fresh meteor impact sites on Mars. “We expected to see them fade as the wind moved the dust around during the months and years after landing, but we’ve been surprised to see that the rate of change doesn’t appear to be consistent.”

One purpose for repeated follow-up imaging of Curiosity’s landing area has been to check whether scientists could model the fading and predict how long it would take for the scars to disappear. Daubar’s work on this aids preparations for NASA’s next Mars lander, InSight, on track for launch in March 2016. The InSight mission will deploy a heat probe that will hammer itself a few yards, or meters, deep into the ground to monitor heat coming from the interior of the planet. The brightness of the ground affects temperature below ground, because a dark surface warms in sunshine more than a bright one does.

HiRISE is one of six instruments with which NASA’s Mars Reconnaissance Orbiter has been studying Mars since 2006.

NASA’s Mars Science Laboratory Project has been using the Curiosity rover to examine ancient Martian environments favorable for microbial life.

With three active NASA Mars orbiters and two Mars rovers, NASA seeks to characterize and understand Mars as a dynamic system, including its present and past environment, climate cycles, geology and biological potential. In parallel on its journey to Mars, NASA is developing the capabilities needed for human missions there.

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp. of Boulder, Colorado. JPL, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter Project, the Mars Science Laboratory Project and the InSight Project for NASA’s Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the orbiter and collaborates with JPL to operate it.

Links for additional info:

About HiRISE:

About NASA’s Mars Reconnaissance Orbiter:

About Curiosity and NASA’s Mars Science Laboratory Project:

About InSight: