MRo

Mars Gullies Likely Not Formed by Liquid Water
External image











NASA - Mars Reconnaissance Orbiter (MRO) logo.

July 29, 2016

External image

Animation above: Martian gullies as seen in the top image from HiRISE on NASA’s Mars Reconnaissance Orbiter resemble gullies on Earth that are carved by liquid water. However, when they are observed with the addition of mineralogical information from CRISM, no evidence for alteration by water appears. Animation Credits: NASA/JPL-Caltech/UA/JHUAPL.

New findings using data from NASA’s Mars Reconnaissance Orbiter show that gullies on modern Mars are likely not being formed by flowing liquid water. This new evidence will allow researchers to further narrow theories about how Martian gullies form, and reveal more details about Mars’ recent geologic processes.

Scientists use the term “gully” for features on Mars that share three characteristics in their shape:  an alcove at the top, a channel, and an apron of deposited material at the bottom. Gullies are distinct from another type of feature on Martian slopes, streaks called “recurring slope lineae,” or RSL, which are distinguished by seasonal darkening and fading, rather than characteristics of how the ground is shaped. Water in the form of hydrated salt has been identified at RSL sites. The new study focuses on gullies and their formation process by adding composition information to previously acquired imaging.

Researchers from the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, examined high-resolution compositional data from more than 100 gully sites throughout Mars. These data, collected by the orbiter’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), were then correlated with images from the same spacecraft’s High Resolution Imaging Science Experiment (HiRISE) camera and Context Camera (CTX).

External image

Images above: Martian gullies as seen in the top image from HiRISE on NASA’s Mars Reconnaissance Orbiter resemble gullies on Earth that are carved by liquid water. However, when they are observed with the addition of mineralogical information from CRISM (bottom), no evidence for alteration by water appears. Images Credits: NASA/JPL-Caltech/UA/JHUAPL.

The findings showed no mineralogical evidence for abundant liquid water or its by-products, thus pointing to mechanisms other than the flow of water – such as the freeze and thaw of carbon dioxide frost – as being the major drivers of recent gully evolution.

The findings were published in Geophysical Research Letters: http://onlinelibrary.wiley.com/doi/10.1002/2016GL068956/full

Gullies are a widespread and common feature on the Martian surface, mostly occurring between 30 and 50 degrees latitude in both the northern and southern hemispheres, generally on slopes that face toward the poles. On Earth, similar gullies are formed by flowing liquid water; however, under current conditions, liquid water is transient on the surface of Mars, and may occur only as small amounts of brine even at RSL streaks. The lack of sufficient water to carve gullies has resulted in a variety of theories for the gullies’ creation, including different mechanisms involving evaporation of water and carbon dioxide frost.

“The HiRISE team and others had shown there was seasonal activity in gullies – primarily in the southern hemisphere – over the past couple of years, and carbon dioxide frost is the main mechanism they suspected of causing it. However, other researchers favored liquid water as the main mechanism,” said Jorge Núñez of APL, the lead author of the paper. “What HiRISE and other imagers were not able to determine on their own was the composition of the material in gullies, because they are optical cameras. To bring another important piece in to help solve the puzzle, we used CRISM, an imaging spectrometer, to look at what kinds of minerals were present in the gullies and see if they could shed light on the main mechanism responsible.”

Núñez and his colleagues took advantage of a new CRISM data product called Map-projected Targeted Reduced Data Records. It allowed them to more easily perform their analyses and then correlate the findings with HiRISE imagery.

External image
Artist’s view of Mars Reconnaissance Orbiter (MRO). Image Credit: NASA
“On Earth and on Mars, we know that the presence of phyllosilicates – clays – or other hydrated minerals indicates formation in liquid water,” Núñez said. “In our study, we found no evidence for clays or other hydrated minerals in most of the gullies we studied, and when we did see them, they were erosional debris from ancient rocks, exposed and transported downslope, rather than altered in more recent flowing water. These gullies are carving into the terrain and exposing clays that likely formed billions of years ago when liquid water was more stable on the Martian surface.”

Other researchers have created computer models that show how sublimation of seasonal carbon dioxide frost can create gullies similar to those observed on Mars, and how their shape can mimic the types of gullies that liquid water would create. The new study adds support to those models.

APL built and operates CRISM, one of six instruments with which the Mars Reconnaissance Orbiter project has been examining Mars since 2006. NASA’s Jet Propulsion Laboratory, a division of the Caltech in Pasadena, California manages the project for the NASA Science Mission Directorate in Washington. Lockheed Martin Space Systems of Denver built the orbiter and supports its operations.

Related links:

Map-projected Targeted Reduced Data Records: http://crism.jhuapl.edu/newscenter/articles/20160317.php

Mars Reconnaissance Orbiter project: http://www.nasa.gov/mro

Mars Reconnaissance Orbiter (MRO): http://www.nasa.gov/mission_pages/MRO/main/index.html

Images (mentioned), Animation (mentioned), Text, Credits; NASA/Tony Greicius/JPL/Guy Webster/Johns Hopkins University Applied Physics Laboratory/Geoff Brown.

Greetings, Orbiter.ch
Full article
6

The Amazing Technicolor Landscape of Mars

High resolution digital terrain models, or DTMs, are topographic maps of Mars as imaged by the High-Resolution Imaging Science Experiment (HiRISE) on board NASA’s Mars Reconnaissance Orbiter (MRO). They are created by grabbing two separate images of the same region of the Martian surface during different orbits. These “stereo pairs” (with different angles of inclination) are used to precisely measure the elevation of the landscape after a complex and time consuming series of steps including calibration by mission scientists and calculations by a powerful algorithm. The result is nothing short of beautiful. So get immersed in Mars’ technicolor landscape and see the scale of some of those awesome geological formations on the Red (blue, green and yellow) Planet. View the entire gallery…

Solar System: Things to Know This Week

The solar system is vast, and exploring it requires not one expedition, but many. From the sun to the Earth to the depths of space beyond Pluto, an entire fleet of spacecraft is pushing back the frontiers of knowledge. Scientists and engineers around the world work together on dozens of missions, and the results of their work unfold on a daily basis. During any given week, astronauts and robotic spacecraft return thousands of pictures and other data from Earth orbit and from half a dozen other worlds.

The result? It’s nothing short of a visual and intellectual feast. For example, all of the following images were obtained over the course of one week during January this year.

The same missions that took these pictures are still at work – they may be photographing Saturn or transmitting a report from Mars as you read this.

1. The Sun

From its clear vantage point in Earth orbit, our Solar Dynamics Observatory (SDO) observes our nearby star almost continuously. This image shows activity on the sun’s surface on Jan. 18. You can also get similar pictures from SDO daily!

2. The Earth from Afar

The DSCOVR satellite orbits the Earth at a distance of nearly a million miles (1.5 million kilometers). It’s Earth Polychromatic Imaging Camera (EPIC) keeps a steady watch on the home planet. This is how the world turned on Jan. 20. Get the latest daily images from EPIC HERE.

3. Mars from Above

The team that manages the Mars Reconnaissance Orbiter (MRO) recently celebrated a decade of observing the Red Planet. MRO took this detailed look at dunes and rocky buttes in Danielson Crater on Jan. 24. It was 3:06 p.m., local Mars time. On the right stide of the image, dust devils have left tracks in the sand.

4. Comet 67/P

The European Space Agency’s Rosetta probe caught this look at the surface of Comet 67/P from a distance of just 46 miles (75 kilometers) on Jan. 23.

5. Saturn

On the same day (Jan. 23), our Cassini spacecraft continued its odyssey of nearly two decades in space, bringing us this look at the sixth planet. See the latest images from Cassini HERE.

Want to learn more? Read our full list of the 10 things to know this week about the solar system HERE.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com

A hole in Mars

What created this unusual hole in Mars? The hole was discovered by chance in 2011 on images of the dusty slopes of Mars' Pavonis Mons volcano taken by the HiRISE instrument aboard the robotic Mars Reconnaissance Orbiter currently circling Mars. The hole appears to be an opening to an underground cavern, partly illuminated on the image right. Analysis of this and follow-up images revealed the opening to be about 35 meters across, while the interior shadow angle indicates that the underlying cavern is roughly 20 meters deep. Why there is a circular crater surrounding this hole remains a topic of speculation, as is the full extent of the underlying cavern. Holes such as this are of particular interest because their interior caves are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life. These pits are therefore prime targets for possible future spacecraft, robots, and even human interplanetary explorers.

Image credit: NASA, JPL, U. Arizona

3

Mars Orbiters ‘Duck and Cover’ for Comet Siding Spring Encounter

NASA is taking steps to protect its Mars orbiters, while preserving opportunities to gather valuable scientific data, as Comet C/2013 A1 Siding Spring heads toward a close flyby of Mars on Oct. 19.

The comet’s nucleus will miss Mars by about 82,000 miles (132,000 kilometers), shedding material hurtling at about 35 miles (56 kilometers) per second, relative to Mars and Mars-orbiting spacecraft. At that velocity, even the smallest particle – estimated to be about one-fiftieth of an inch (half a millimeter) across – could cause significant damage to a spacecraft.

NASA currently operates two Mars orbiters, with a third on its way and expected to arrive in Martian orbit just a month before the comet flyby. Teams operating the orbiters plan to have all spacecraft positioned on the opposite side of the Red Planet when the comet is most likely to pass by.

The European Space Agency is taking

similar precautions

to protect its Mars Express (MEX) orbiter.

  • For more information about the Mars flyby of comet Siding Spring, click here.
Credit: NASA/JPL-Caltech

Winter View of Dunes

Looking a bit like chocolate mountains with forests of chocolate pine trees, these are in fact dunes from the southern hemisphere on Mars during the winter-time. The brighter tones are thought to be carbon dioxide or water frost. This is an enhanced-color view generated from images acquired by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter (MRO).

4

Mind-Blowing Beauty of Mars’ Dunes: HiRISE Photos

Mars plays host to a huge number of dune fields – regions where fine wind-blown material gets deposited to form arguably some of the most beautiful dunes that can be found on any planetary body in the solar system. Using the powerful High-Resolution Imaging Science Experiment (HiRISE) camera on board NASA’s Mars Reconnaissance Orbiter, planetary scientists have an orbital view on these features that aid our understanding of aeolian (wind-formed) processes and Martian geology. Here are some of our favorite Mars dunes as seen by HiRISE.

Dark Sand Cascades on Mars

They might look like trees on Mars, but they’re not. Groups of dark brown streaks have been photographed by the Mars Reconnaissance Orbiter on melting pinkish sand dunes covered with light frost.

Image Credit: HiRISE, MRO, LPL (U. Arizona), NASA

The above image was taken in 2008 April near the North Pole of Mars. At that time, dark sand on the interior of Martian sand dunes became more and more visible as the spring Sun melted the lighter carbon dioxide ice.

When occurring near the top of a dune, dark sand may cascade down the dune leaving dark surface streaks – streaks that might appear at first to be trees standing in front of the lighter regions, but cast no shadows.

Objects about 25 centimeters across are resolved on this image spanning about one kilometer. Close ups of some parts of this image show billowing plumes indicating that the sand slides were occurring even when the image was being taken.

Ancient Flood Channels Cut Deep into Mars

Relatively recently, water blasted out from an underground aquifer on Mars, carving out deep flood channels in the surface that were later buried by lava flows, radar images complied from an orbiting NASA probe shows.

In a nutshell, the Mars Reconnaissance Orbiter has used radar to look inside Mars’ crust, under a layer of ancient lava, exposing a valley that was formed by a huge surge of water! If that’s not crazycool, I don’t know what is.

Dead Spacecraft on Mars Spotted in New Photos

A NASA probe orbiting Mars has captured new photos of two dead spacecraft frozen in place at their Red Planet graves.

The photos were taken by NASA’s powerful Mars Reconnaissance Orbiter (MRO), which has been circling the planet since 2006.

The spacecraft first spied NASA’s dead Phoenix Mars Lander in the Martian arctic on Jan. 26 in a color photo that reveals the lander and its frigid surroundings as they appeared following Phoenix’s second winter on the planet. The Phoenix spacecraft landed successfully on Mars in 2008.

In a separate photo, MRO also spotted the three-petal landing platform that delivered NASA’s Mars rover Spirit to the surface of the Red Planet in January 2004. The platform used parachutes and airbags to bounce to a stop on Gusev crater so the Spirit rover could begin its mission.

Seasonal changes on Mars

Researchers using NASA’s Mars Reconnaissance Orbiter see seasonal changes on far-northern Martian sand dunes caused by warming of a winter blanket of frozen carbon dioxide.

Earth has no naturally frozen carbon dioxide, though pieces of manufactured carbon-dioxide ice, called “dry ice,” sublime directly from solid to gas on Earth, just as the vast blankets of dry ice do on Mars. A driving factor in the springtime changes where seasonal coverings of dry ice form on Mars is that thawing occurs at the underside of the ice sheet, where it is in contact with dark ground being warmed by early-spring sunshine through translucent ice. The trapped gas builds up pressure and breaks out in various ways.

Transient grooves form on dunes when gas trapped under the ice blanket finds an escape point and whooshes out, carrying out sand with it. The expelled sand forms dark fans or streaks on top of the ice layer at first, but this evidence disappears with the seasonal ice, and summer winds erase most of the grooves in the dunes before the next winter.

The findings reinforce growing appreciation that Mars today, however different from its former self, is still a dynamic world, and however similar to Earth in some respects, displays some quite unearthly processes.

With three Martian years (six Earth years) of data in hand from the Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE) camera, the researchers report on the sequence and variety of seasonal changes. The spring changes include outbursts of gas carrying sand, polygonal cracking of the winter ice blanketing the dunes, sandfalls down the faces of the dunes, and dark fans of sand propelled out onto the ice.

Image credit: NASA/JPL-Caltech/Univ. of Arizona

Weird Geological Features Spied on Mars

The High-Resolution Imaging Science Experiment (HiRISE) camera carried by NASA’s Mars Reconnaissance Orbiter (MRO) has spotted a strange geological feature that, for now, defies an obvious explanation. Found at the southern edge of Acidalia Planitia, small pits with raised edges appear to hug a long ridge. So far, mission scientists have ruled out impact craters and wind as formation processes, but have pegged the most likely cause to be glacial in nature.