SCIENCE IN MOTION
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For a view of refereed articles using HiRISE data, click here.
The Current Martian Cratering Rate
I. J. Daubar, A. S. McEwen, S. Byrne, M. R. Kennedy, B. Ivanov
Abstract
The discovery of 248 dated impact sites known to have formed within the last few decades allows us to refine the current cratering rate and slope of the production function at Mars. We use a subset of 44 of these new craters that were imaged before and after impact by Mars Reconnaissance Orbiter's Context Camera -- a thoroughly searched data set that minimizes biases from variable image resolutions. We find the current impact rate is 1.65×10-6 craters with an effective diameter ≥ 3.9 meters / km2 / year, with a differential slope (power-law exponent) of -2.45 ± 0.36. This results in model ages that are factors of three to five below the Hartmann (2005) and Neukum et al. (2001)/Ivanov (2001) model production functions where they overlap in diameter. The best-fit production function we measure has a shallower slope than model functions at these sizes, but model function slopes are within the statistical errors. More than half of the impacts in this size range form clusters, which is another reason to use caution when estimating surface ages using craters smaller than ~50 meters in diameter.
Article on ScienceDirect
See also:
JPL/NASA release
UANews release
Examples of craters listed in this paper (Click for larger version)
I. J. Daubar, A. S. McEwen, S. Byrne, M. R. Kennedy, B. Ivanov
Abstract
The discovery of 248 dated impact sites known to have formed within the last few decades allows us to refine the current cratering rate and slope of the production function at Mars. We use a subset of 44 of these new craters that were imaged before and after impact by Mars Reconnaissance Orbiter's Context Camera -- a thoroughly searched data set that minimizes biases from variable image resolutions. We find the current impact rate is 1.65×10-6 craters with an effective diameter ≥ 3.9 meters / km2 / year, with a differential slope (power-law exponent) of -2.45 ± 0.36. This results in model ages that are factors of three to five below the Hartmann (2005) and Neukum et al. (2001)/Ivanov (2001) model production functions where they overlap in diameter. The best-fit production function we measure has a shallower slope than model functions at these sizes, but model function slopes are within the statistical errors. More than half of the impacts in this size range form clusters, which is another reason to use caution when estimating surface ages using craters smaller than ~50 meters in diameter.
Article on ScienceDirect
See also:
JPL/NASA release
UANews release
Examples of craters listed in this paper (Click for larger version)
Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes
C.J. Hansen, S. Byrne, G. Portyankina, M. Bourke, C. Dundas, A. McEwen, M. Mellon, A. Pommerol, N. Thomas
Abstract
Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels (“araneiform” terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.
C.J. Hansen, S. Byrne, G. Portyankina, M. Bourke, C. Dundas, A. McEwen, M. Mellon, A. Pommerol, N. Thomas
Abstract
Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels (“araneiform” terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.
See also:
Partial List of Observations in this Paper
Earth-like sand fluxes on Mars
N.T. Bridges, F. Ayoub, J-P. Avouac, S. Leprince, A. Lucas & S. Mattson
Abstract
Strong and sustained winds on Mars have been considered rare, on the basis of surface meteorology measurements and global circulation models, raising the question of whether the abundant dunes and evidence for wind erosion seen on the planet are a current process. Recent studies showed sand activity, but could not determine whether entire dunes were moving—implying large sand fluxes—or whether more localized and surficial changes had occurred. Here we present measurements of the migration rate of sand ripples and dune lee fronts at the Nili Patera dune field. We show that the dunes are near steady state, with their entire volumes composed of mobile sand. The dunes have unexpectedly high sand fluxes, similar, for example, to those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar.
Read the UANews press release
Read the Nature article
Observations in this Paper
PSP_004339_1890
PSP_005684_1890 (captioned image)
ESP_017762_1890
ESP_018039_1890
Digital terrain model
Animated GIFs
PSP_004339_1890 and PSP_005684_1890
PSP_005684_1890 and ESP_017762_1890 (October 2007 and May 2010)
N.T. Bridges, F. Ayoub, J-P. Avouac, S. Leprince, A. Lucas & S. Mattson
Abstract
Strong and sustained winds on Mars have been considered rare, on the basis of surface meteorology measurements and global circulation models, raising the question of whether the abundant dunes and evidence for wind erosion seen on the planet are a current process. Recent studies showed sand activity, but could not determine whether entire dunes were moving—implying large sand fluxes—or whether more localized and surficial changes had occurred. Here we present measurements of the migration rate of sand ripples and dune lee fronts at the Nili Patera dune field. We show that the dunes are near steady state, with their entire volumes composed of mobile sand. The dunes have unexpectedly high sand fluxes, similar, for example, to those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar.
Read the UANews press release
Read the Nature article
Observations in this Paper
PSP_004339_1890
PSP_005684_1890 (captioned image)
ESP_017762_1890
ESP_018039_1890
Digital terrain model
Animated GIFs
PSP_004339_1890 and PSP_005684_1890
PSP_005684_1890 and ESP_017762_1890 (October 2007 and May 2010)
Seasonal Flows on Warm Martian Slopes
Alfred S. McEwen, Lujendra Ojha, Colin M. Dundas, Sarah S. Mattson, Shane Byrne, James J. Wray, Selby C. Cull, Scott L. Murchie, Nicolas Thomas, Virginia C. Gulick
Abstract
Water likely flowed across ancient Mars, but whether it ever exists as a liquid on the surface today remains debatable. Recurring slope lineae (RSL) are narrow (0.5-5 m), relatively dark markings on steep (25°-40°) slopes; repeat MRO/HiRISE images show them to appear and incrementally grow during warm seasons and fade in cold seasons. They extend downslope from bedrock outcrops, often associated with small channels, and hundreds of them form in rare locations. RSL appear and lengthen in the late southern spring/summer from 48°S to 32°S latitudes favoring equator-facing slopes--times and places with peak surface temperatures from ~250-300 K. Liquid brines near the surface might explain this activity, but the exact mechanism and source of water are not understood.
Science: Is Mars Weeping Salty Tears?
Read the University of Arizona press release
View our breakout page for this paper
Alfred S. McEwen, Lujendra Ojha, Colin M. Dundas, Sarah S. Mattson, Shane Byrne, James J. Wray, Selby C. Cull, Scott L. Murchie, Nicolas Thomas, Virginia C. Gulick
Abstract
Water likely flowed across ancient Mars, but whether it ever exists as a liquid on the surface today remains debatable. Recurring slope lineae (RSL) are narrow (0.5-5 m), relatively dark markings on steep (25°-40°) slopes; repeat MRO/HiRISE images show them to appear and incrementally grow during warm seasons and fade in cold seasons. They extend downslope from bedrock outcrops, often associated with small channels, and hundreds of them form in rare locations. RSL appear and lengthen in the late southern spring/summer from 48°S to 32°S latitudes favoring equator-facing slopes--times and places with peak surface temperatures from ~250-300 K. Liquid brines near the surface might explain this activity, but the exact mechanism and source of water are not understood.
Science: Is Mars Weeping Salty Tears?
Read the University of Arizona press release
View our breakout page for this paper
Seasonal Erosion and Restoration of Mars’ Northern Polar Dunes
C. J. Hansen, M. Bourke, N. T. Bridges, S. Byrne, C. Colon, S. Diniega, C. Dundas, K. Herkenhoff, A. McEwen, M. Mellon, G. Portyankina, and N. Thomas
Abstract
Despite radically different environmental conditions, terrestrial and Martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here we show that Martian dunes are subject to an additional modification process not found on the Earth: springtime sublimation of Mars’ CO2 seasonal polar caps. Numerous dunes in Mars’ north polar region have experienced morphological changes within a Mars year, detected in images acquired by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO). Dunes show new alcoves, gullies, and dune apron extension. This is followed by remobilization of the fresh deposits by the wind, forming ripples and erasing gullies. The widespread nature of these rapid changes, and the pristine appearance of most dunes in the area, implicates active sand transport in the vast polar erg in Mars’ current climate.
Full article in Science
Read the University of Arizona press release
Observations in this article
PSP_007962_2635 | PSP_008968_2650 | PSP_009105_2640 | PSP_009324_2650 | ESP_015935_2640
ESP_016256_2635 | ESP_016546_2635 | ESP_016836_2635 | ESP_017768_2640 | ESP_017974_2650
PSP_010019_2635 | ESP_018036_2635
C. J. Hansen, M. Bourke, N. T. Bridges, S. Byrne, C. Colon, S. Diniega, C. Dundas, K. Herkenhoff, A. McEwen, M. Mellon, G. Portyankina, and N. Thomas
Abstract
Despite radically different environmental conditions, terrestrial and Martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here we show that Martian dunes are subject to an additional modification process not found on the Earth: springtime sublimation of Mars’ CO2 seasonal polar caps. Numerous dunes in Mars’ north polar region have experienced morphological changes within a Mars year, detected in images acquired by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO). Dunes show new alcoves, gullies, and dune apron extension. This is followed by remobilization of the fresh deposits by the wind, forming ripples and erasing gullies. The widespread nature of these rapid changes, and the pristine appearance of most dunes in the area, implicates active sand transport in the vast polar erg in Mars’ current climate.
Full article in Science
Read the University of Arizona press release
Observations in this article
PSP_007962_2635 | PSP_008968_2650 | PSP_009105_2640 | PSP_009324_2650 | ESP_015935_2640
ESP_016256_2635 | ESP_016546_2635 | ESP_016836_2635 | ESP_017768_2640 | ESP_017974_2650
PSP_010019_2635 | ESP_018036_2635
Discovery of Columnar Jointing on Mars
M.P. Milazzo, L.P. Keszthelyi, W.L. Jaeger, M. Rosiek, S. Mattson, C. Verba, R.A. Beyer, P.E. Geissler, A.S. McEwen, and the HiRISE Team
Abstract
We report on the discovery of columnar jointing in Marte Valles, Mars. These columnar lavas were discovered in the wall of a pristine, 16-km-diameter impact crater and exhibit the features of terrestrial columnar basalts. There are discontinuous outcrops along the entire crater wall, suggesting that the columnar rocks covered a surface area of at least 200 sq. km, assuming that the rocks obliterated by the impact event were similarly jointed. We also see columns in the walls of other fresh craters in the nearby volcanic plains of Elysium Planitia-Amazonis Planitia, which include Marte Vallis, and in a well-preserved crater in northeast Hellas.
Full article in Geology
Read the USGS news release
Observation cited in this article
PSP_005917_2020
Spring at the South Pole of Mars
C.J.Hansen, A. McEwen
Download the presentation (PDF, 3MB)
Observations in this presentation
PSP_005579_0935 | PSP_003730_0945 | PSP_003443_0980 | PSP_003364_0945 | PSP_003179_0945
PSP_003113_0940 | PSP_003087_0930 | PSP_002942_0935 | PSP_002651_0930 | PSP_002622_0945
PSP_002532_0935
C.J.Hansen, A. McEwen
Download the presentation (PDF, 3MB)
Observations in this presentation
PSP_005579_0935 | PSP_003730_0945 | PSP_003443_0980 | PSP_003364_0945 | PSP_003179_0945
PSP_003113_0940 | PSP_003087_0930 | PSP_002942_0935 | PSP_002651_0930 | PSP_002622_0945
PSP_002532_0935
 | ||
| A Closer Look at Water-Related Geologic Activity on Mars
Alfred S. McEwen
HiRISE images reveal (1) abundant boulders in surface units previously interpreted as fine-grained deposits
from water or the air; (2) further evidence for water-carved gullies, although the most recent bright gully deposits
could have been dry flows; and (3) evidence that recent large craters were the result of impact into volatile-rich ground.
These results should help focus future exploration of Mars.
Read the article Download the "Science" cover image Cover image (PSP_003583_1425) 4048 x 5082; 59 MB Flyover movie (QuickTime) 320 x 180 (2.3 MB) 480 x 270 (5.8 MB) 640 x 360 (11 MB) Original observation for the above image PSP_003583_1425 List of images cited in this paper TRA_000846_2475 PSP_001964_2275 PSP_001810_2175 PSP_002172_1410 PSP_002932_1445 PSP_001714_1415 PSP_001846_1415 PSP_001481_1875 PSP_001978_1445 PSP_003596_1435 PSP_004229_1435 PSP_001846_2390 PSP_001508_2400 PSP_002200_1380 PSP_002812_1330 PSP_003252_1425 PSP_003942_2120 PSP_001538_2035 PSP_002158_2035 
Meter-scale Morphology of the North Polar Region of Mars
Kenneth E. Herkenhoff
With detailed images from the HiRISE camera, a dome of layered ice deposits on the north pole of Mars comes into sharper
focus, showing evidence of recent mass wasting, flow and debris accumulation.
Read the article Flyover movie (QuickTime) 320 x 180 (5.9 MB) 480 x 270 (17.6 MB) 640 x 360 (21.3 MB) Orignal observation for the above image PSP_001636_2760 List of Images cited in this paper TRA_000845_2645 TRA_000863_2640 PSP_001412_2650 PSP_001488_2665 PSP_001550_2640 PSP_001738_2670  |
Athabasca Valles, Mars: A Lava-Draped Channel System
Windy L. Jaeger
NASA Probe Counts Space Rock Impacts on Mars
Researchers have identified 248 new impact sites on parts of the Martian surface in the past decade, using images from the spacecraft to determine when the craters appeared. The 200-per-year planetwide estimate is a calculation based on the number found in a systematic survey of a portion of the planet.
MRO's High Resolution Imaging Science Experiment (HiRISE) camera took pictures of the fresh craters at sites where before-and-after images by other cameras bracketed when the impacts occurred. This combination provided a new way to make direct measurements of the impact rate on Mars. This will lead to better age estimates of recent features on Mars, some of which may have been the result of climate change.
"It's exciting to find these new craters right after they form," said Ingrid Daubar of the University of Arizona, Tucson, lead author of the paper published online this month by the journal Icarus. "It reminds you Mars is an active planet, and we can study processes that are happening today."
These asteroids or comet fragments typically are no more than 3 to 6 feet (1 to 2 meters) in diameter. Space rocks too small to reach the ground on Earth cause craters on Mars because the Red Planet has a much thinner atmosphere.
HiRISE targeted places where dark spots had appeared during the time between images taken by the spacecraft's Context Camera (CTX) or cameras on other orbiters. The new estimate of cratering rate is based on a portion of the 248 new craters detected. If comes from a systematic check of a dusty fraction of the planet with CTX since late 2006. The impacts disturb the dust, creating noticeable blast zones. In this part of the research, 44 fresh impact sites were identified.
The meteor over Chelyabinsk, Russia, in February was about 10 times bigger than the objects that dug the fresh Martian craters.
Estimates of the rate at which new craters appear serve as scientists' best yardstick for estimating the ages of exposed landscape surfaces on Mars and other worlds.
Daubar and co-authors calculated a rate for how frequently new craters at least 12.8 feet (3.9 meters) in diameter are excavated. The rate is equivalent to an average of one each year on each area of the Martian surface roughly the size of the U.S. state of Texas. Earlier estimates pegged the cratering rate at three to 10 times more craters per year. They were based on studies of craters on the moon and the ages of lunar rocks collected during NASA's Apollo missions in the late 1960s and early 1970s.
"Mars now has the best-known current rate of cratering in the solar system," said HiRISE Principal Investigator Alfred McEwen of the University of Arizona, a co-author on the paper.
MRO has been examining Mars with six instruments since 2006.
"The longevity of this mission is providing wonderful opportunities for investigating changes on Mars," said MRO Deputy Project Scientist Leslie Tamppari of NASA's Jet Propulsion Laboratory, Pasadena, Calif.
The University of Arizona Lunar and Planetary Laboratory operates the HiRISE camera, which was built by Ball Aerospace & Technologies Corp. of Boulder, Colo. Malin Space Science Systems of San Diego built and operates the Context Camera. JPL manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems of Denver, built the orbiter.
To see images of the craters, visit:
http://uahirise.org/sim
For more information about HiRISE, visit:
http://hirise.lpl.arizona.edu
For more about MRO, visit:
http://www.nasa.gov/mro
Windy L. Jaeger
Athabasca Valles is a young 'outflow' channel system in the equatorial region of Mars. Most researchers agree
that it was carved by catastrophic floods of water, and some believe that frozen floodwaters survive to this day
on the channel floor. However, new HiRISE observations reveal that Athabasca Valles is entirely coated by a
thin veneer of solidified lava. The lava poured from a fissure, filled the channels, and then drained
downstream leaving behind a thin layer of hard rock to coat and preserve the channel system.
Read the article
Flyover movie (QuickTime)
320 x 180 (5.6 MB)
480 x 270 (9.6 MB)
640 x 360 (25.4 MB)
Original observation for the above image
PSP_003294_1985
List of Images cited in this paper
PSP_001408_1900
Stereo pair PSP_001606_1900 and PSP_002226_1900
Stereo pair PSP_001540_1890 and PSP_002371_1890
Stereo pair PSP_002938_1890 and PSP_003083_1890
Stereo pair PSP_002661_1895 and PSP_003294_1895
Stereo pair PSP_002174_1875 and PSP_002292_1875
Read the article
Flyover movie (QuickTime)
320 x 180 (5.6 MB)
480 x 270 (9.6 MB)
640 x 360 (25.4 MB)
Original observation for the above image
PSP_003294_1985
List of Images cited in this paper
PSP_001408_1900
Stereo pair PSP_001606_1900 and PSP_002226_1900
Stereo pair PSP_001540_1890 and PSP_002371_1890
Stereo pair PSP_002938_1890 and PSP_003083_1890
Stereo pair PSP_002661_1895 and PSP_003294_1895
Stereo pair PSP_002174_1875 and PSP_002292_1875
NASA Probe Counts Space Rock Impacts on Mars
WASHINGTON
-- Scientists using images from NASA's Mars Reconnaissance Orbiter
(MRO) have estimated that the planet is bombarded by more than 200 small
asteroids or bits of comets per year forming craters at least 12.8 feet
(3.9 meters) across.
Researchers have identified 248 new impact sites on parts of the Martian surface in the past decade, using images from the spacecraft to determine when the craters appeared. The 200-per-year planetwide estimate is a calculation based on the number found in a systematic survey of a portion of the planet.
MRO's High Resolution Imaging Science Experiment (HiRISE) camera took pictures of the fresh craters at sites where before-and-after images by other cameras bracketed when the impacts occurred. This combination provided a new way to make direct measurements of the impact rate on Mars. This will lead to better age estimates of recent features on Mars, some of which may have been the result of climate change.
"It's exciting to find these new craters right after they form," said Ingrid Daubar of the University of Arizona, Tucson, lead author of the paper published online this month by the journal Icarus. "It reminds you Mars is an active planet, and we can study processes that are happening today."
These asteroids or comet fragments typically are no more than 3 to 6 feet (1 to 2 meters) in diameter. Space rocks too small to reach the ground on Earth cause craters on Mars because the Red Planet has a much thinner atmosphere.
HiRISE targeted places where dark spots had appeared during the time between images taken by the spacecraft's Context Camera (CTX) or cameras on other orbiters. The new estimate of cratering rate is based on a portion of the 248 new craters detected. If comes from a systematic check of a dusty fraction of the planet with CTX since late 2006. The impacts disturb the dust, creating noticeable blast zones. In this part of the research, 44 fresh impact sites were identified.
The meteor over Chelyabinsk, Russia, in February was about 10 times bigger than the objects that dug the fresh Martian craters.
Estimates of the rate at which new craters appear serve as scientists' best yardstick for estimating the ages of exposed landscape surfaces on Mars and other worlds.
Daubar and co-authors calculated a rate for how frequently new craters at least 12.8 feet (3.9 meters) in diameter are excavated. The rate is equivalent to an average of one each year on each area of the Martian surface roughly the size of the U.S. state of Texas. Earlier estimates pegged the cratering rate at three to 10 times more craters per year. They were based on studies of craters on the moon and the ages of lunar rocks collected during NASA's Apollo missions in the late 1960s and early 1970s.
"Mars now has the best-known current rate of cratering in the solar system," said HiRISE Principal Investigator Alfred McEwen of the University of Arizona, a co-author on the paper.
MRO has been examining Mars with six instruments since 2006.
"The longevity of this mission is providing wonderful opportunities for investigating changes on Mars," said MRO Deputy Project Scientist Leslie Tamppari of NASA's Jet Propulsion Laboratory, Pasadena, Calif.
The University of Arizona Lunar and Planetary Laboratory operates the HiRISE camera, which was built by Ball Aerospace & Technologies Corp. of Boulder, Colo. Malin Space Science Systems of San Diego built and operates the Context Camera. JPL manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems of Denver, built the orbiter.
To see images of the craters, visit:
http://uahirise.org/sim
For more information about HiRISE, visit:
http://hirise.lpl.arizona.edu
For more about MRO, visit:
http://www.nasa.gov/mro
NASA
Guillermo Gonzalo Sanchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
Inscríbete en el Foro del blog y participa : A Vuelo De Un Quinde - El Foro!
Guillermo Gonzalo Sanchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
Inscríbete en el Foro del blog y participa : A Vuelo De Un Quinde - El Foro!
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