Link to a Watery Past
In this image from NASA's Curiosity rover, a rock outcrop called Link pops out from a Martian surface that is elsewhere blanketed by reddish-brown dust. The fractured Link outcrop has blocks of exposed, clean surfaces. Rounded gravel fragments, or clasts, up to a couple inches (few centimeters) in size are in a matrix of white material. Many gravel-sized rocks have eroded out of the outcrop onto the surface, particularly in the left portion of the frame. The outcrop characteristics are consistent with a sedimentary conglomerate, or a rock that was formed by the deposition of water and is composed of many smaller rounded rocks cemented together. Water transport is the only process capable of producing the rounded shape of clasts of this size.The Link outcrop was imaged with the 100-millimeter Mast Camera on Sept. 2, 2012, which was the 27th sol, or Martian day of operations.
The name Link is derived from a significant rock formation in the Northwest Territories of Canada, where there is also a lake with the same name.
Scientists enhanced the color in this version to show the Martian scene as it would appear under the lighting conditions we have on Earth, which helps in analyzing the terrain.
Image credit: NASA/JPL-Caltech/MSSS
Where Water Flowed Downslope
This image shows the topography, with shading added, around the area where NASA's Curiosity rover landed on Aug. 5 PDT (Aug. 6 EDT). Higher elevations are colored in red, with cooler colors indicating transitions downslope to lower elevations. The black oval indicates the targeted landing area for the rover known as the "landing ellipse," and the cross shows where the rover actually landed.An alluvial fan, or fan-shaped deposit where debris spreads out downslope, has been highlighted in lighter colors for better viewing. On Earth, alluvial fans often are formed by water flowing downslope. New observations from Curiosity of rounded pebbles embedded with rocky outcrops provide concrete evidence that water did flow in this region on Mars, creating the alluvial fan. Water carrying the pebbly material is thought to have streamed downslope extending the alluvial fan, at least occasionally, to where the rover now sits studying its ancient history.
Elevation data were obtained from stereo processing of images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.
Image credit: NASA/JPL-Caltech/UofA
Curiosity's Roadside Discoveries
This map shows the path on Mars of NASA's Curiosity rover toward Glenelg, an area where three terrains of scientific interest converge. Arrows mark geological features encountered so far that led to the discovery of what appears to be an ancient Martian streambed. The first site, dubbed Goulburn, is an area where the thrusters from the rover's descent stage blasted away a layer of loose material, exposing bedrock underneath. Goulburn gave scientists a hint that water might have transported the pebbly sandstone material making up the outcrop. The second feature, a naturally exposed rock outcrop named Link, stood out to the science team for its embedded, rounded gravel pieces. Such rounded shapes are strong evidence of water transport. The final feature, another naturally exposed rock outcrop named Hottah, offered the most compelling evidence yet of an ancient stream, as it contains abundant rounded pebbles. The grain sizes are also an important part of the evidence for water: the rounded pebbles, which are up to 1.6 inches (4 centimeters) in size, are too large to have been transported by wind.The image used for the map is from an observation of the landing site by the High Resolution Imaging Science Experiment (HiRISE) instrument on NASA's Mars Reconnaissance Orbiter.
Image credit: NASA/JPL-Caltech/Univ. of Arizona
Rock Outcrops on Mars and Earth
This set of images compares the Link outcrop of rocks on Mars (left) with similar rocks seen on Earth (right). The image of Link, obtained by NASA's Curiosity rover, shows rounded gravel fragments, or clasts, up to a couple inches (few centimeters), within the rock outcrop. Erosion of the outcrop results in gravel clasts that fall onto the ground, creating the gravel pile at left. The outcrop characteristics are consistent with a sedimentary conglomerate, or a rock that was formed by the deposition of water and is composed of many smaller rounded rocks cemented together. A typical Earth example of sedimentary conglomerate formed of gravel fragments in a stream is shown on the right.An annotated version of the image highlights a piece of gravel that is about 0.4 inches (1 centimeter) across. It was selected as an example of coarse size and rounded shape. Rounded grains (of any size) occur by abrasion in sediment transport, by wind or water, when the grains bounce against each other. Gravel fragments are too large to be transported by wind. At this size, scientists know the rounding occurred in water transport in a stream.
› Unannotated version
The name Link is derived from a significant rock formation in the Northwest Territories of Canada, where there is also a lake with the same name.
Scientists enhanced the color in the Mars image to show the scene as it would appear under the lighting conditions we have on Earth, which helps in analyzing the terrain. The Link outcrop was imaged with the 100-millimeter Mast Camera on Sept. 2, 2012, which was the 27th sol, or Martian day of operations.
Image credit: NASA/JPL-Caltech/MSSS and PSI
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› Full SizeRemnants of Ancient Streambed on Mars
NASA's Curiosity rover found evidence for an ancient, flowing stream on Mars at a few sites, including the rock outcrop pictured here, which the science team has named "Hottah" after Hottah Lake in Canada’s Northwest Territories. It may look like a broken sidewalk, but this geological feature on Mars is actually exposed bedrock made up of smaller fragments cemented together, or what geologists call a sedimentary conglomerate. Scientists theorize that the bedrock was disrupted in the past, giving it the titled angle, most likely via impacts from meteorites.The key evidence for the ancient stream comes from the size and rounded shape of the gravel in and around the bedrock. Hottah has pieces of gravel embedded in it, called clasts, up to a couple inches (few centimeters) in size and located within a matrix of sand-sized material. Some of the clasts are round in shape, leading the science team to conclude they were transported by a vigorous flow of water. The grains are too large to have been moved by wind.
A close-up view of Hottah reveals more details of the outcrop. Broken surfaces of the outcrop have rounded, gravel clasts, such as the one circled in white, which is about 1.2 inches (3 centimeters) across. Erosion of the outcrop results in gravel clasts that protrude from the outcrop and ultimately fall onto the ground, creating the gravel pile at left.
This image mosaic was taken by Curiosity's 100-millimeter Mastcam telephoto lens on its 39th Martian day, or sol, of the mission (Sept. 14, 2012 PDT/Sept. 15 GMT).
Image credit: NASA/JPL-Caltech/MSSS
PASADENA, Calif. -- NASA's Curiosity rover mission has found evidence a
stream once ran vigorously across the area on Mars where the rover is
driving. There is earlier evidence for the presence of water on Mars,
but this evidence -- images of rocks containing ancient streambed
gravels -- is the first of its kind.
Scientists are studying the images of stones cemented into a layer of
conglomerate rock. The sizes and shapes of stones offer clues to the
speed and distance of a long-ago stream's flow.
"From the size of gravels it carried, we can interpret the water was
moving about 3 feet per second, with a depth somewhere between ankle and
hip deep," said Curiosity science co-investigator William Dietrich of
the University of California, Berkeley. "Plenty of papers have been
written about channels on Mars with many different hypotheses about the
flows in them. This is the first time we're actually seeing
water-transported gravel on Mars. This is a transition from speculation
about the size of streambed material to direct observation of it."
The finding site lies between the north rim of Gale Crater and the base
of Mount Sharp, a mountain inside the crater. Earlier imaging of the
region from Mars orbit allows for additional interpretation of the
gravel-bearing conglomerate. The imagery shows an alluvial fan of
material washed down from the rim, streaked by many apparent channels,
sitting uphill of the new finds.
The rounded shape of some stones in the conglomerate indicates
long-distance transport from above the rim, where a channel named Peace
Vallis feeds into the alluvial fan. The abundance of channels in the fan
between the rim and conglomerate suggests flows continued or repeated
over a long time, not just once or for a few years.
The discovery comes from examining two outcrops, called "Hottah" and
"Link," with the telephoto capability of Curiosity's mast camera during
the first 40 days after landing. Those observations followed up on
earlier hints from another outcrop, which was exposed by thruster
exhaust as Curiosity, the Mars Science Laboratory Project's rover,
touched down.
"Hottah looks like someone jack-hammered up a slab of city sidewalk, but
it's really a tilted block of an ancient streambed," said Mars Science
Laboratory Project Scientist John Grotzinger of the California Institute
of Technology in Pasadena.
The gravels in conglomerates at both outcrops range in size from a grain
of sand to a golf ball. Some are angular, but many are rounded.
"The shapes tell you they were transported and the sizes tell you they
couldn't be transported by wind. They were transported by water flow,"
said Curiosity science co-investigator Rebecca Williams of the Planetary
Science Institute in Tucson, Ariz.
The science team may use Curiosity to learn the elemental composition of
the material, which holds the conglomerate together, revealing more
characteristics of the wet environment that formed these deposits. The
stones in the conglomerate provide a sampling from above the crater rim,
so the team may also examine several of them to learn about broader
regional geology.
The slope of Mount Sharp in Gale Crater remains the rover's main
destination. Clay and sulfate minerals detected there from orbit can be
good preservers of carbon-based organic chemicals that are potential
ingredients for life.
"A long-flowing stream can be a habitable environment," said Grotzinger.
"It is not our top choice as an environment for preservation of
organics, though. We're still going to Mount Sharp, but this is
insurance that we have already found our first potentially habitable
environment."
During the two-year prime mission of the Mars Science Laboratory,
researchers will use Curiosity's 10 instruments to investigate whether
areas in Gale Crater have ever offered environmental conditions
favorable for microbial life.
NASA's Jet Propulsion Laboratory, a division of Caltech, built Curiosity
and manages the Mars Science Laboratory Project for NASA's Science
Mission Directorate, Washington.
For more about Curiosity, visit:
and
You can follow the mission on Facebook and Twitter at:
and
Guy Webster / D.C. Agle 818-354-5011
Jet Propulsion Laboratory, Pasadena,Calif.
guy.webster@jpl.nasa.gov / agle@jpl.nasa.gov
Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov
Jet Propulsion Laboratory, Pasadena,Calif.
guy.webster@jpl.nasa.gov / agle@jpl.nasa.gov
Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov
NASA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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