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Topic Name: Researchers has Found Liquid Water on the Martian Surface of Mars Within the Last Decade

Category: STAR (Space, Telecommunications & Radioscience)

Research persons: Jon D. Pelletier

Location: University of Arizona in Tucson, United States

Details

Liquid water has not been found on the Martian surface within the last decade after all, according to new research.

The finding casts doubt on the 2006 report that the bright spots in some Martian gullies indicate that liquid water flowed down those gullies sometime since 1999.

"It rules out pure liquid water," said lead author Jon D. Pelletier of The University of Arizona in Tucson.

Pelletier and his colleagues used topographic data derived from images of Mars from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. Since 2006, HiRISE has been providing the most detailed images of Mars ever taken from orbit.

The researchers applied the basic physics of how fluid flows under Martian conditions to determine how a flow of pure liquid water would look on the HiRISE images versus how an avalanche of dry granular debris such as sand and gravel would look.

"The dry granular case was the winner," said Pelletier, a UA associate professor of geosciences. "I was surprised. I started off thinking we were going to prove it's liquid water."

Finding liquid water on the surface of Mars would indicate the best places to look for current life on Mars, said co-author Alfred S. McEwen, a UA professor of planetary sciences.

"What we'd hoped to do was rule out the dry flow model -- but that didn't happen," said McEwen, the HiRISE principal investigator and director of UA's Planetary Image Research Laboratory.

An avalanche of dry debris is a much better match for their calculations and also what their computer model predicts, said Pelletier and McEwen.

Pelletier said, "Right now the balance of evidence suggests that the dry granular case is the most probable."

They added that their research does not rule out the possibility that the images show flows of very thick mud containing about 50 percent to 60 percent sediment. Such mud would have a consistency similar to molasses or hot lava. From orbit, the resulting deposit would look similar to that from a dry avalanche.

The team's research article, "Recent bright gully deposits on Mars: wet or dry flow?" is being published in the March issue of Geology. Pelletier and McEwen's co-authors are Kelly J. Kolb, a UA doctoral candidate, and Randy L. Kirk of the U.S. Geological Survey in Flagstaff, Arizona.

NASA funded the research.

In December 2006, Michael Malin and his colleagues published an article in the journal Science suggesting the bright streaks that formed in two Martian gullies since 1999 "suggest that liquid water flowed on the surface of Mars during the past decade."

Malin's team used images taken by the Mars Global Surveyor Mars Orbital Camera (MOC) of gullies that had formed before 1999. Repeat images taken of the gullies in 2006 showed bright streaks that had not been there in the earlier images.

Subsequently, Pelletier and McEwen were at a scientific meeting and began chatting about the astonishing new finding. They discussed how the much more detailed images from HiRISE might be used to flesh out the Malin team's findings.

Pelletier had experience in using the stereoscopic computer-generated topographic maps known as digital elevation models (DEMs) to figure out how particular landscape features form.

DEMs are made using images of the landscape taken from two different angles. The Mars Reconnaissance Orbiter spacecraft is designed to regularly point at targets, enabling high-resolution stereo images, McEwen said.

Kirk made a DEM of the crater in the Centauri Montes region where the Malin team found a new bright streak in a gully.

Once the DEM was constructed, Pelletier used the topographic information along with a commercially available numerical computer model to predict how deposits in that particular gully would appear if left by a pure water flood versus how the deposits would appear if left by a dry avalanche.

The model also predicted specific conditions needed to create each type of debris flow.

"This is the first time that anyone has applied numerical computer models to the bright deposits in gullies on Mars or to DEMs produced from HiRISE images," Pelletier said.

When he compared the actual conditions of the bright deposit and its HiRISE image to the predictions made by the model, the dry avalanche model was a better fit.

"The dry granular case is both simpler and more closely matches the observations," Pelletier said.

"It's just a test," he said. It's either more like A or more like B. We were surprised that it was more like B."

Pelletier said these new findings indicate, "There are other ways of getting deposits that look just like this one that do not require water."

One of the team's next steps is using HiRISE images to examine similar bright deposits on less-steep slopes to sort out what processes might have formed those deposits.

Note for Digital Elevation Model (DEM)
A digital elevation model (DEM) is a digital representation of ground surface topography or terrain. It is also widely known as a digital terrain model (DTM). A DEM can be represented as a raster (a grid of squares) or as a triangular irregular network. DEMs are commonly built using remote sensing techniques, however, they may also be built from land surveying. DEMs are used often in geographic information systems, and are the most common basis for digitally-produced relief maps.
Digital elevation models may be prepared in a number of ways, but they are frequently obtained by remote sensing rather than direct survey. One powerful technique for generating digital elevation models is interferometric synthetic aperture radar; two passes of a radar satellite (such as RADARSAT-1) suffice to generate a digital elevation map tens of kilometers on a side with a resolution of around ten meters. One also obtains an image of the surface cover.
Another powerful technique for generating a Digital Elevation Model is using the Digital image correlation method. It implies two optical images acquired with different angles taken from the same pass of an airplane or an Earth Observation satellite (such as the HRS intrument of SPOT5).
Older methods of generating DEMs often involve interpolating digital contour maps that may have been produced by direct survey of the land surface; this method is still used in mountain areas, where interferometry is not always satisfactory. Note that the contour data or any other sampled elevation datasets (by GPS or ground survey) are not DEMs, but may be considered Digital terrain models. A DEM implies that elevation is available continuously at each location in the study area.
The quality of a DEM is a measure of how accurate elevation is at each pixel (absolute accuracy) and how accurately is the morphology presented (relative accuracy). Several factors play an important role for quality of DEM-derived products:
terrain roughness;
sampling density (elevation data collection method);
grid resolution or pixel size;
interpolation algorithm;
vertical resolution;
terrain analysis algorithm
Common uses of DEMs include:
extracting terrain parameters
modeling water flow or mass movement (for example avalanches)
creation of relief maps
rendering of 3D visualizations.
creation of physical models (including raised-relief maps)
rectification of aerial photography or satellite imagery.
reduction (terrain correction) of gravity measurements (gravimetry, physical geodesy).
terrain analyses in geomorphology and physical geography

About High Resolution Imaging Science Experiment Camera
The High Resolution Imaging Science Experiment camera is a camera onboard the Mars Reconnaissance Orbiter. The 65 kg, $40 million (USD) instrument was built under the direction of the University of Arizona's Lunar and Planetary Laboratory by Ball Aerospace & Technologies Corp.. It consists of a 0.5 meter reflecting telescope, the largest of any deep space mission, which allows it to take pictures with resolutions up to 0.3 m resolving objects about a meter across, or the size of a beachball.
The HiRISE camera is designed to view surface features of Mars in greater detail than has previously been possible. This allows for the study of the age of Martian features, looking for landing sites for future Mars landers, and in general, seeing the Martian surface in far greater detail than has previously been done from orbit. By doing so, it is allowing better studies of Martian channels and valleys, volcanic landforms, possible former lakes and oceans, and other surface landforms as they exist on the Martian surface.
The general public will soon be allowed to request sites to take pictures of Mars with the HiRISE camera. For this reason, and due to the unprecedented access of pictures to the general public, shortly after they have been received and processed, the camera has taken the philosophy "The People's Camera".
HiRISE was designed to be a High Resolution camera from the beginning. It consists of a large mirror, as well as a large CCD camera. Because of this, it achieves a resolution of 1 microradian, or 0.3 meter at a height of 300 km. (For comparison purposes, satellite images on Google Maps are available to 1 meter.) It can image in three color bands, 400–600 nm (blue-green or B-G), 550–850 nm (red) and 800–1,000 nm (near infrared or NIR).
Red color images are at 20,264 pixels wide (6 km in a 300 km orbit), and Green-Blue and NIR are at 4,048 pixels wide (1.2 km). HiRISE's onboard computer reads out these lines in time with the orbiter's ground speed, meaning the images are potentially unlimited in height. Practically this is limited by the onboard computer's 28 Gb memory capacity. The nominal maximum resolution of red images is 20,000 × 40,000 pixels, or 800 megapixels and 4,000 × 40,000 pixels (160 megapixels) for the narrower images of the B-G and NIR bands. A single uncompressed image uses 16.4 Gb. However, these images are transmitted compressed, at a total size of 5 Gigabits. These images are released to the general public on the HiRISE website via a new format called JPEG 2000.
To facilitate the mapping of potential landing sites, HiRISE can produce stereo pairs of images from which the topography can be measured to an accuracy of 0.25 meter.

About Mars Global Surveyor
The Mars Global Surveyor (MGS) was a US spacecraft developed by NASA and the Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 20-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when it lost contact with NASA in November 2006.
On November 2, 2006, the spacecraft failed to respond to messages and commands. A faint signal was detected three days later which indicated that the craft had gone into safe mode. All attempts to recontact the Mars Global Surveyor and resolve the problem failed. In January 2007 NASA officially ended the mission.
The Surveyor spacecraft, fabricated at the Lockheed Martin Astronautics plant in Denver, is a rectangular-shaped box with wing-like projections (solar panels, used to convert sunlight into electricity) extending from opposite sides. When fully loaded with propellant at the time of launch, the spacecraft weighed 1,060 kilograms (2,342 pounds). Most of Surveyor's mass lies in the box-shaped module occupying the center portion of the spacecraft. This center module is made of two smaller rectangular modules stacked on top of each other, one of which is called the equipment module and holds the spacecraft's electronics, science instruments, and the 1750A mission computer. The other module, called the propulsion module, houses Surveyor's rocket engines and propellant tanks.
Five scientific instruments fly onboard Mars Global Surveyor:
MOC - the Mars Orbiter Camera, operated by Malin Space Science Systems
MOLA - the Mars Orbiter Laser Altimeter
TES - the Thermal Emission Spectrometer
MAG/ER - a Magnetometer and electron reflectometer
USO/RS Ultrastable Oscilator for Doppler measurements
MR Mars Relay - Signal receiver

About Mars Reconnaissance Orbiter
NASA's Mars Reconnaissance Orbiter (MRO) is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. The $720 million USD spacecraft was built by Lockheed Martin under the supervision of the Jet Propulsion Laboratory. It was launched August 12, 2005, and attained Martian orbit on March 10, 2006. In November 2006, after five months of aerobraking, it entered its final science orbit and began its primary science phase.
MRO contains a host of scientific instruments such as cameras, spectrometers, and radar, which are used to analyze the landforms, stratigraphy, minerals, and ice of Mars. It paves the way for future spacecraft by monitoring daily weather and surface conditions, studying potential landing sites, and hosting a new telecommunications system. MRO's telecommunications system will transfer more data back to Earth than all previous interplanetary missions combined, and MRO will serve as a highly capable relay satellite for future missions.
MRO joined five other spacecraft studying Mars: Mars Global Surveyor, Mars Express, Mars Odyssey, and two Mars Exploration Rovers.
MRO was first proposed to NASA in 1999, as the Mars Surveyor Orbiter, an orbiting satellite whose hallmark was a high-resolution camera. It was one of two missions being considered for the 2003 Mars launch window; however, during the proposal process the orbiter lost against what became known as the Mars Exploration Rovers. The orbiter mission was rescheduled for launch in 2005, and NASA announced its final name, Mars Reconnaissance Orbiter, on October 26, 2000.
MRO is modeled after NASA's highly successful Mars Global Surveyor to conduct surveillance of Mars from orbit. Early specifications of the satellite included a large camera to take high resolution pictures of Mars. In this regard, Jim Garvin, the Mars exploration program scientist for NASA, proclaimed that MRO would be a "microscope in orbit". The satellite was also to include a visible-near-infrared spectrograph.
On October 3, 2001, NASA chose Lockheed Martin as the primary contractor for the spacecraft's fabrication. By the end of 2001 all of the mission's instruments were selected. There were no major setbacks during MRO's construction, and the spacecraft was moved to John F. Kennedy Space Center on May 1, 2005 to prepare it for launch.
MRO science operations will last two Earth years, from November 2006 to November 2008. One of the mission's main goals is to map the Martian landscape with its high-resolution cameras in order to choose landing sites for future surface missions. The MRO played an important role in choosing the landing site of the Phoenix Lander, which will explore the Martian Arctic. The initial site chosen by scientists was imaged with the HiRISE camera and found to be littered with boulders. After analysis with HiRISE and the Mars Odyssey's THEMIS a new site was chosen. Mars Science Laboratory, a highly maneuverable rover, will also have its landing site inspected. The MRO will also provide critical navigation data during their landings and act as a telecommunications relay.
MRO is using its on-board scientific equipment to study the Martian climate, weather, atmosphere, and geology, and to search for signs of water in the polar caps and underground. In addition, MRO is looking for the remains of the previously lost Mars Polar Lander and Beagle 2 spacecraft, and serves as the first step in setting up an internet protocol network for the planets in our solar system. After its main science operations are completed, the probe's extended mission is to be the communication and navigation system for landers and rover probes.

In figure 1, Artist's redition of HiRISE at Mars

In figure 2, Jon D. Pelletier is an associate professor of geosciences at the University of Arizona in Tucson

In figure 3, The image on the left is a portion of a High Resolution Imaging Science Experiment image showing a bright streak in a gully on the side of a crater in the Centauri Montes region of Mars. The two colored images were generated by the researchers' numerical computer model. The middle image shows how a deposit left by a pure liquid water flood would appear in the gully. The right-hand streak shows the deposit that would be left by a dry debris flow. Only the model for the dry debris flow generated the same fingering as seen in the HiRISE image.

In figure 4, Mars Reconnaissance Orbiter