Difference between revisions of "Dark slope streaks"

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(More clear information on appearance.)
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==Appearance==
 
==Appearance==
  
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Perhaps some of the prettiest landscapes on Mars, dark slope streaks are found on dust-covered slopes, particular near the equator.<ref name=Chuang10>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref>  However, much of their beauty comes from the post-processing of the images. They are adjusted to bring out more detail by setting the darkest part of the image to black. Streaks are actually only about 10% darker than their surroundings.  <ref>Sullivan, R. et al.  2001.  Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>
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Dark slope streaks are found on dust-covered slopes, particular near the equator.<ref name="Chuang10">Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref>   
  
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Typically, streaks begin at a small point high on a steep slope, such as a crater wall.<ref name= Schorghofer02>Schorghofer, N.; Aharonson, O.; Khatiwala, S.  2002.  Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref>  And then they  greatly widen and sometimes divide into finger-like extensions (digitation).  Obstacles, such as boulders, may cause an individual streak to split into two separate streaks or eventually form a braided (anastomosing) pattern.<ref> Chuang, F.C. et al.  2007. HiRISE Observations of Slope Streaks on Mars. Geophys. Res. Lett., 34 L20204.</ref>  Many have a fan shape. <ref> Sullivan, R. et al.  2001.  Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>
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The streaks start out only about 10% darker than their surrounds <ref>Sullivan, R. et al.  2001.  Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref> (This is confused because many images of the streaks have been post-processed to bring out more detail and appear much darker). Over time these streaks tend to get lighter as the brighter Martian dust settles from the atmosphere. The darker ones are the newest.
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Typically, streaks begin at a small point high on a steep slope, such as a crater wall.<ref name="Schorghofer02">Schorghofer, N.; Aharonson, O.; Khatiwala, S.  2002.  Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref>  And then they  greatly widen and sometimes divide into finger-like extensions (digitation).  Obstacles, such as boulders, may cause an individual streak to split into two separate streaks or eventually form a braided (anastomosing) pattern.<ref>Chuang, F.C. et al.  2007. HiRISE Observations of Slope Streaks on Mars. Geophys. Res. Lett., 34 L20204.</ref>  Many have a fan shape. <ref>Sullivan, R. et al.  2001.  Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>
  
 
Streaks may be hundreds of meters long with a width of 20 to 200 meters.  Indeed, some can be over 2 kilometers long.  
 
Streaks may be hundreds of meters long with a width of 20 to 200 meters.  Indeed, some can be over 2 kilometers long.  
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<ref> Sullivan, R. et al.  2001.  Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>
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<ref>Sullivan, R. et al.  2001.  Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>
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<ref> Chuang, F.C.; Beyer, R.A.; Bridges, N.T.  2010.  Modification of Martian Slope Streaks by Eolian Processes. Icarus, 205 154–164.</ref>
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<ref>Chuang, F.C.; Beyer, R.A.; Bridges, N.T.  2010.  Modification of Martian Slope Streaks by Eolian Processes. Icarus, 205 154–164.</ref>
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<ref> Baratoux, D. et al.  2006.  The Role of the Wind-Transported Dust in Slope Streaks Activity: Evidence from the HRSC Data. Icarus, 183 30–45.</ref>
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<ref>Baratoux, D. et al.  2006.  The Role of the Wind-Transported Dust in Slope Streaks Activity: Evidence from the HRSC Data. Icarus, 183 30–45.</ref>
  
 
<gallery class="center" widths="190px" heights="180px">
 
<gallery class="center" widths="190px" heights="180px">
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</gallery>
 
</gallery>
  
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== How long do they last? ==
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==How long do they last?==
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Thanks to the many excellent cameras that we have placed in orbit over many decades, we have a history of how the Martian surface changes.  Dark slope streaks are some of the most changing parts of Mars.  They were discovered in Viking Orbiter pictures from the 1970,<ref name=Morris82>Morris, E.C. (1982). Aureole Deposits of the Martian Volcano Olympus Mons. ''J. Geophys. Res.,'' '''87'''(B2), 1164–1178.</ref> <ref name=Ferguson84>Ferguson,H.M.; Lucchitta, B.K. (1984). Dark Streaks on Talus Slopes, Mars in ''Reports of the Planetary Geology Program 1983, NASA Tech. Memo., TM-86246,'' pp. 188–190. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840015363_1984015363.pdf.</ref>  When images from Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) spacecraft are examined, the life history of streaks can be precisely determined.<ref>Sullivan, R. et al. (2001). Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633. </ref> <ref name=Chuang07>Chuang, F.C. et al.  2007.  HiRISE Observations of Slope Streaks on Mars. 'Geophys. Res. Lett.  34 L20204.</ref> <ref>Dundas, C. 2018. HIRISE OBSERVATIONS OF NEW MARTIAN SLOPE STREAKS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2026.pdf</ref> <ref> Malin, M.C.; Edgett, K.S. (2001). Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission. J. Geophys. Res., 106(E10), 23,429–23,570.</ref>  
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Thanks to the many excellent cameras that we have placed in orbit over many decades, we have a history of how the Martian surface changes.  Dark slope streaks are some of the most changing parts of Mars.  They were discovered in Viking Orbiter pictures from the 1970,<ref name="Morris82">Morris, E.C. (1982). Aureole Deposits of the Martian Volcano Olympus Mons. ''J. Geophys. Res.,'' '''87'''(B2), 1164–1178.</ref> <ref name="Ferguson84">Ferguson,H.M.; Lucchitta, B.K. (1984). Dark Streaks on Talus Slopes, Mars in ''Reports of the Planetary Geology Program 1983, NASA Tech. Memo., TM-86246,'' pp. 188–190. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840015363_1984015363.pdf.</ref>  When images from Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) spacecraft are examined, the life history of streaks can be precisely determined.<ref>Sullivan, R. et al. (2001). Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633. </ref> <ref name="Chuang07">Chuang, F.C. et al.  2007.  HiRISE Observations of Slope Streaks on Mars. 'Geophys. Res. Lett.  34 L20204.</ref> <ref>Dundas, C. 2018. HIRISE OBSERVATIONS OF NEW MARTIAN SLOPE STREAKS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2026.pdf</ref> <ref>Malin, M.C.; Edgett, K.S. (2001). Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission. J. Geophys. Res., 106(E10), 23,429–23,570.</ref> <ref>Edgett, K.S.; Malin, M.C.; Sullivan, R.J.; Thomas, P.; Veverka, J. (2000). Dynamic Mars: New Dark Slope Streaks Observed on Annual and Decadal Time Scales. 31st Lunar and Planetary Science Conference, Abstract #1058. http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1058.pdf.</ref>
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<ref> Edgett, K.S.; Malin, M.C.; Sullivan, R.J.; Thomas, P.; Veverka, J. (2000). Dynamic Mars: New Dark Slope Streaks Observed on Annual and Decadal Time Scales. 31st Lunar and Planetary Science Conference, Abstract #1058. http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1058.pdf.</ref>
 
  
 
[[File:New Streaks Formed PIA02379.jpg|right|thumb|320px|New slope streaks formed near Apollinaris Mons between February 1998 and November 1999, as seen by Mars Orbital Camera (MOC).]]
 
[[File:New Streaks Formed PIA02379.jpg|right|thumb|320px|New slope streaks formed near Apollinaris Mons between February 1998 and November 1999, as seen by Mars Orbital Camera (MOC).]]
  
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One analysis concluded that 70 streaks per day may form on the planet.  The research team compared overlapping  images from Mars Global Surveyor Mars Orbiter Camera that were spaced days to years apart. <ref> Aharonson, O.; Schorghofer, N.; Gerstell, M.F. (2003). Slope Streak Formation and Dust Deposition Rates on Mars. J. Geophys. Res., 108(E12), 5138, doi:10.1029/2003JE002123. </ref>
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One analysis concluded that 70 streaks per day may form on the planet.  The research team compared overlapping  images from Mars Global Surveyor Mars Orbiter Camera that were spaced days to years apart. <ref>Aharonson, O.; Schorghofer, N.; Gerstell, M.F. (2003). Slope Streak Formation and Dust Deposition Rates on Mars. J. Geophys. Res., 108(E12), 5138, doi:10.1029/2003JE002123. </ref>
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Dark slope streaks are constantly forming and fading.  The darker ones are the youngest.  Fading is accomplished by settling of bright dust in the Martian atmosphere.  When researches looked at a small area (Lycus Sulci) on Mars with both Viking images and recent CTX images from the Mars Reconnaissance Orbiter, they found that the ones seen in Viking photos were gone, however, new streaks have taken their place.  Their calculations indicated that slope streaks last about 40 years <ref> Bergonio, J., K. Rottas, and N. Schorghofer. 2013. Properties of martian slope streak populations: 225.  Icarus: 194-199.</ref>  From time to time the entire globe of Mars is enveloped in a dust storm.  Many, perhaps most streaks and other features are erased during those periods.<ref> Aharonson, O.; Schorghofer, N.; Gerstell, M.F.  2003. S lope Streak Formation and Dust Deposition Rates on Mars. J. Geophys. Res., 108(E12), 5138, doi:10.1029/2003JE002123.</ref> <ref> Schorghofer, Aharonson, O.; Gerstell, M.F.; Tatsumi, L.  2007.  Three Decades of Slope Streak Activity on Mars.  Icarus:  191, 132–140.  doi:10.1016/j.icarus.2007.04.026.</ref>
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Dark slope streaks are constantly forming and fading.  The darker ones are the youngest.  Fading is accomplished by settling of bright dust in the Martian atmosphere.  When researches looked at a small area (Lycus Sulci) on Mars with both Viking images and recent CTX images from the Mars Reconnaissance Orbiter, they found that the ones seen in Viking photos were gone, however, new streaks have taken their place.  Their calculations indicated that slope streaks last about 40 years <ref>Bergonio, J., K. Rottas, and N. Schorghofer. 2013. Properties of martian slope streak populations: 225.  Icarus: 194-199.</ref>  From time to time the entire globe of Mars is enveloped in a dust storm.  Many, perhaps most streaks and other features are erased during those periods.<ref>Aharonson, O.; Schorghofer, N.; Gerstell, M.F.  2003. S lope Streak Formation and Dust Deposition Rates on Mars. J. Geophys. Res., 108(E12), 5138, doi:10.1029/2003JE002123.</ref> <ref>Schorghofer, Aharonson, O.; Gerstell, M.F.; Tatsumi, L.  2007.  Three Decades of Slope Streak Activity on Mars.  Icarus:  191, 132–140.  doi:10.1016/j.icarus.2007.04.026.</ref>
  
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<gallery class="center" widths="190px" heights="180px">
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<gallery class="center" widths="190px" heights="180px">
  
 
File:23677streakslabeled.jpg|Young and old dark slope streaks with origins labeled.
 
File:23677streakslabeled.jpg|Young and old dark slope streaks with origins labeled.
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==What causes dark slope streaks?==
 
==What causes dark slope streaks?==
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Although many ideas have been put forward to explain slope streaks, the general opinion today is that they are simply avalanches of darker colored dust.<ref> Treiman, A.H.; Louge, M.Y. (2004). Martian Slope Streaks and Gullies: Origins as Dry Granular Flows. 35th Lunar and Planetary Science Conference, Abstract #1323. http://www.lpi.usra.edu/meetings/lpsc2004/pdf/1323.pdf</ref>  Nearly all of Mars is covered with a thin, bright dust.  On steep slopes this layer of dust can move away and reveal a dark surface.  The dark volcanic rock basalt lies under the lighter-toned dust which falls out of the atmosphere.
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Although many ideas have been put forward to explain slope streaks, the general opinion today is that they are simply avalanches of darker colored dust.<ref>Treiman, A.H.; Louge, M.Y. (2004). Martian Slope Streaks and Gullies: Origins as Dry Granular Flows. 35th Lunar and Planetary Science Conference, Abstract #1323. http://www.lpi.usra.edu/meetings/lpsc2004/pdf/1323.pdf</ref>  Nearly all of Mars is covered with a thin, bright dust.  On steep slopes this layer of dust can move away and reveal a dark surface.  The dark volcanic rock basalt lies under the lighter-toned dust which falls out of the atmosphere.
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With the long term observations from orbit, researchers have noticed that strikes by meteorites can start the process of slope formation.<ref> http://www.uahirise.org/epo/nuggets/dust-avalanche.pdf</ref> <ref>https://hirise.lpl.arizona.edu/ESP_054066_1920</ref>  Moreover, even the air blast from an oncoming strike can trigger clusters of slopes to form.<ref>Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar.  2012.  Impact air blast triggers dust avalanches on Mars  Icarus:  217 (1) 194 doi:10.1016/j.icarus.2011.10.026</ref>
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With the long term observations from orbit, researchers have noticed that strikes by meteorites can start the process of slope formation.<ref>http://www.uahirise.org/epo/nuggets/dust-avalanche.pdf</ref> <ref>https://hirise.lpl.arizona.edu/ESP_054066_1920</ref>  Moreover, even the air blast from an oncoming strike can trigger clusters of slopes to form.<ref>Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar.  2012.  Impact air blast triggers dust avalanches on Mars  Icarus:  217 (1) 194 doi:10.1016/j.icarus.2011.10.026</ref>
 
<gallery class="center" widths="190px" heights="180px">
 
<gallery class="center" widths="190px" heights="180px">
 
File:ESP 054066 1920newstreak.jpg|New dark slope streak that was triggered by an impact  Location is the Arabia quadrangle
 
File:ESP 054066 1920newstreak.jpg|New dark slope streak that was triggered by an impact  Location is the Arabia quadrangle
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<ref>Malin, M.; Edgett, K. (2000). "Evidence for recent groundwater seepage and surface runoff on Mars". Science. 288: 2330–2335.</ref>
 
<ref>Malin, M.; Edgett, K. (2000). "Evidence for recent groundwater seepage and surface runoff on Mars". Science. 288: 2330–2335.</ref>
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<ref> Luu, K., et al. 2018. GULLY FORMATION ON THE NORTHWESTERN SLOPE OF PALIKIR CRATER, MARS 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2650.pdf</ref>   
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<ref>Luu, K., et al. 2018. GULLY FORMATION ON THE NORTHWESTERN SLOPE OF PALIKIR CRATER, MARS 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2650.pdf</ref>   
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<ref> Hamid, S., V. Gulick. 2018. GEOMORPHOLOGICAL ANALYSIS OF GULLIES ALONG WESTERN SLOPES OF PALIKIR CRATER. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2644.pdf</ref>   
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<ref>Hamid, S., V. Gulick. 2018. GEOMORPHOLOGICAL ANALYSIS OF GULLIES ALONG WESTERN SLOPES OF PALIKIR CRATER. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2644.pdf</ref>   
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<ref> Tyler Paladin, T., et al. 2018. INSIGHTS INTO THE FORMATION OF GULLIES IN ASIMOV CRATER, MARS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2889.pdf</ref>      Now, new observations suggest that gullies are being made today by chunks of dry ice moving down steep slopes in the spring.  
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<ref>Tyler Paladin, T., et al. 2018. INSIGHTS INTO THE FORMATION OF GULLIES IN ASIMOV CRATER, MARS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2889.pdf</ref>      Now, new observations suggest that gullies are being made today by chunks of dry ice moving down steep slopes in the spring.  
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<ref> Dundas, C., S. Diniega, A. McEwen. 2015. Long-term monitoring of martian gully formation and evolution with MRO/HiRISE. Icarus: 251, 244–263</ref>   
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<ref>Dundas, C., S. Diniega, A. McEwen. 2015. Long-term monitoring of martian gully formation and evolution with MRO/HiRISE. Icarus: 251, 244–263</ref>   
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<ref>   Fergason, R., C. Dundas, R. Anderson. 2015. IN-DEPTH REGIONAL ASSESSMENT OF THERMOPHYSICAL PROPERTIES OF ACTIVE GULLIES ON MARS. 46th Lunar and Planetary Science Conference. 2009.pdf</ref>   
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<ref>Fergason, R., C. Dundas, R. Anderson. 2015. IN-DEPTH REGIONAL ASSESSMENT OF THERMOPHYSICAL PROPERTIES OF ACTIVE GULLIES ON MARS. 46th Lunar and Planetary Science Conference. 2009.pdf</ref>   
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<ref>   Dundas, C. et al. 2016. HOW WET IS RECENT MARS? INSIGHTS FROM GULLIES AND RSL. 47th Lunar and Planetary Science Conference (2016) 2327.pdf. </ref>   
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<ref>Dundas, C. et al. 2016. HOW WET IS RECENT MARS? INSIGHTS FROM GULLIES AND RSL. 47th Lunar and Planetary Science Conference (2016) 2327.pdf. </ref>   
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<ref> Vincendon, M.  2015.  Identification of Mars gully activity
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<ref>Vincendon, M.  2015.  Identification of Mars gully activity
 
types associated with ice composition.JGR:120, 1859–1879. </ref>   
 
types associated with ice composition.JGR:120, 1859–1879. </ref>   
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<ref> Raack, J.; et al. (2015). "Present-day seasonal gully activity in a south polar pit (Sisyphi Cavi) on Mars". Icarus. 251: 226–243. Bibcode:2015Icar..251..226R. doi:10.1016/j.icarus.2014.03.040. </ref>   
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<ref>Raack, J.; et al. (2015). "Present-day seasonal gully activity in a south polar pit (Sisyphi Cavi) on Mars". Icarus. 251: 226–243. Bibcode:2015Icar..251..226R. doi:10.1016/j.icarus.2014.03.040. </ref>   
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<ref>   http://www.uahirise.org/ESP_044327_1375</ref>   
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<ref>http://www.uahirise.org/ESP_044327_1375</ref>   
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<ref>   C. Pilorget, C., F. Forget. 2015. "CO2 Driven Formation of Gullies on Mars." 46th Lunar and Planetary Science Conference. 2471.pdf</ref>   
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<ref>C. Pilorget, C., F. Forget. 2015. "CO2 Driven Formation of Gullies on Mars." 46th Lunar and Planetary Science Conference. 2471.pdf</ref>   
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<ref> Pilorget, C.; Forget, F. (2016). "Formation of gullies on Mars by debris flows triggered by CO2 sublimation". Nature Geoscience. 9: 65–69. Bibcode:2016NatGe...9...65P. </ref>   
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<ref>Pilorget, C.; Forget, F. (2016). "Formation of gullies on Mars by debris flows triggered by CO2 sublimation". Nature Geoscience. 9: 65–69. Bibcode:2016NatGe...9...65P. </ref>   
 
As the map below shows gullies and streaks are found in different areas on the planet.
 
As the map below shows gullies and streaks are found in different areas on the planet.
 
<gallery class="center" widths="190px" heights="180px">
 
<gallery class="center" widths="190px" heights="180px">
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[[File:50858 1435gullies.jpg|600pxr|Image of gullies with main parts labeled.  The main parts of a Martian gully are alcove, channel, and apron.  Picture was taken by HiRISE under HiWish program.]]
 
[[File:50858 1435gullies.jpg|600pxr|Image of gullies with main parts labeled.  The main parts of a Martian gully are alcove, channel, and apron.  Picture was taken by HiRISE under HiWish program.]]
  
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Like gullies and streaks, recurring slope lineae are seen on steep slopes, but they are smaller, more narrow, and straighter.  Since they seem to lengthen as the temperature increases, they were believed to be involved with liquid water.  <ref> McEwen, A. et al.  2011.  Seasonal Flows on Warm Martian Slopes. Science, 333(6043), 740–743. doi:10.1126/science.1204816 PMID 21817049. http://www.sciencemag.org/content/333/6043/740. </ref>   
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Like gullies and streaks, recurring slope lineae are seen on steep slopes, but they are smaller, more narrow, and straighter.  Since they seem to lengthen as the temperature increases, they were believed to be involved with liquid water.  <ref>McEwen, A. et al.  2011.  Seasonal Flows on Warm Martian Slopes. Science, 333(6043), 740–743. doi:10.1126/science.1204816 PMID 21817049. http://www.sciencemag.org/content/333/6043/740. </ref>   
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<ref> Mann, Adam (18 February 2014). "Strange Dark Streaks on Mars Get More and More Mysterious". Wired. Retrieved 18 February 2014. </ref>   
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<ref>Mann, Adam (18 February 2014). "Strange Dark Streaks on Mars Get More and More Mysterious". Wired. Retrieved 18 February 2014. </ref>   
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<ref> Chang, K.  2011.  "Scientists Find Signs Water Is Flowing on Mars," New York Times, August 4, A13. https://www.nytimes.com/2011/08/05/science/space/05mars.html?_r=1&ref=marsplanet. </ref>   
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<ref>Chang, K.  2011.  "Scientists Find Signs Water Is Flowing on Mars," New York Times, August 4, A13. https://www.nytimes.com/2011/08/05/science/space/05mars.html?_r=1&ref=marsplanet. </ref>   
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<ref>   HiRISE website. Seasonal Flows on Warm Martian Slopes. http://hirise.lpl.arizona.edu/sim/science-2011-aug-4.php. </ref>   
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<ref>HiRISE website. Seasonal Flows on Warm Martian Slopes. http://hirise.lpl.arizona.edu/sim/science-2011-aug-4.php. </ref>   
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<ref> McEwen, A. Ojha L.; Dundas C.; Mattson, S.; Byrne S.; Wray J.; Cull S.; Murchie S.  2011.  Transient Slope Lineae: Evidence for Summertime Briny Flows on Mars? 42nd Lunar and Planetary Science Conference, Abstract #2314. http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2314.pdf. </ref>   
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<ref>McEwen, A. Ojha L.; Dundas C.; Mattson, S.; Byrne S.; Wray J.; Cull S.; Murchie S.  2011.  Transient Slope Lineae: Evidence for Summertime Briny Flows on Mars? 42nd Lunar and Planetary Science Conference, Abstract #2314. http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2314.pdf. </ref>   
 
Nevertheless, later studies showed that very little water, if any, could be involved.<ref>Dundas, C., et al.  2017.  Granular Flows at Recurring Slope Lineae on Mars Indicate a Limited Role for Liquid Water. Nature Geoscience. Nov. 20. [1].</ref> <ref>Schaefer, E., et al.  2018.  A case study of recurring slope lineae (RSL) at Tivat crater: Implications for RSL origins. Icarus: In press. https://doi.org/10.1016/j.icarus.2018.07.014</ref>
 
Nevertheless, later studies showed that very little water, if any, could be involved.<ref>Dundas, C., et al.  2017.  Granular Flows at Recurring Slope Lineae on Mars Indicate a Limited Role for Liquid Water. Nature Geoscience. Nov. 20. [1].</ref> <ref>Schaefer, E., et al.  2018.  A case study of recurring slope lineae (RSL) at Tivat crater: Implications for RSL origins. Icarus: In press. https://doi.org/10.1016/j.icarus.2018.07.014</ref>
 
<gallery class="center" widths="190px" heights="180px">
 
<gallery class="center" widths="190px" heights="180px">
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</gallery>
 
</gallery>
  
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== References ==
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==References==
 
{{reflist}}
 
{{reflist}}
  
 
==See also==
 
==See also==
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* [[Martian gullies]]
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* [[What Mars Actually Looks Like! ]]  
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*[[Martian gullies]]
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== External links ==
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*[[What Mars Actually Looks Like! ]]
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* [[yt:_sUUKcZaTgA|Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]]
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==External links==
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*[[yt:_sUUKcZaTgA|Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]]

Revision as of 09:19, 23 September 2018

Dark slope streaks, as seen by HiRISE

Dark slope streaks are found on Mars on dust-covered slopes often near the equator, they are believed to be avalanches involving darker martian dust.

Appearance

Dark slope streaks are found on dust-covered slopes, particular near the equator.[1]

The streaks start out only about 10% darker than their surrounds [2] (This is confused because many images of the streaks have been post-processed to bring out more detail and appear much darker). Over time these streaks tend to get lighter as the brighter Martian dust settles from the atmosphere. The darker ones are the newest.

Typically, streaks begin at a small point high on a steep slope, such as a crater wall.[3] And then they greatly widen and sometimes divide into finger-like extensions (digitation). Obstacles, such as boulders, may cause an individual streak to split into two separate streaks or eventually form a braided (anastomosing) pattern.[4] Many have a fan shape. [5]

Streaks may be hundreds of meters long with a width of 20 to 200 meters. Indeed, some can be over 2 kilometers long. [6] [7] [8]

  • Close view of dark slope streaks

  • Streak being affected by boulders. Arrows indicate boulders and resulting effect on streak.

  • Close view of streak showing boulders causing streak to divide

How long do they last?

Thanks to the many excellent cameras that we have placed in orbit over many decades, we have a history of how the Martian surface changes. Dark slope streaks are some of the most changing parts of Mars. They were discovered in Viking Orbiter pictures from the 1970,[9] [10] When images from Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) spacecraft are examined, the life history of streaks can be precisely determined.[11] [12] [13] [14] [15]

New slope streaks formed near Apollinaris Mons between February 1998 and November 1999, as seen by Mars Orbital Camera (MOC).

One analysis concluded that 70 streaks per day may form on the planet. The research team compared overlapping images from Mars Global Surveyor Mars Orbiter Camera that were spaced days to years apart. [16] Dark slope streaks are constantly forming and fading. The darker ones are the youngest. Fading is accomplished by settling of bright dust in the Martian atmosphere. When researches looked at a small area (Lycus Sulci) on Mars with both Viking images and recent CTX images from the Mars Reconnaissance Orbiter, they found that the ones seen in Viking photos were gone, however, new streaks have taken their place. Their calculations indicated that slope streaks last about 40 years [17] From time to time the entire globe of Mars is enveloped in a dust storm. Many, perhaps most streaks and other features are erased during those periods.[18] [19]

  • Young and old dark slope streaks with origins labeled.

  • Mars without a dust storm on June 2001 (on left) and with a global dust storm on July 2001 (on right), as seen by Mars Global Surveyor

What causes dark slope streaks?

Although many ideas have been put forward to explain slope streaks, the general opinion today is that they are simply avalanches of darker colored dust.[20] Nearly all of Mars is covered with a thin, bright dust. On steep slopes this layer of dust can move away and reveal a dark surface. The dark volcanic rock basalt lies under the lighter-toned dust which falls out of the atmosphere. With the long term observations from orbit, researchers have noticed that strikes by meteorites can start the process of slope formation.[21] [22] Moreover, even the air blast from an oncoming strike can trigger clusters of slopes to form.[23]

  • New dark slope streak that was triggered by an impact Location is the Arabia quadrangle

Other slope features

Several features are common on slopes on Mars. The surface of Mars is billions of years old in most places. Consequently, it has accumulated many steep slopes, especially in craters and canyons. Although streaks, gullies, and recurring slope lineae all occur on slopes, they have different origins. Martian gullies show up in certain zones. However, unlike dark slope streaks they go fairly deep into the surface and are not erased by falling dust over time. Their origin is still debated. For over a decade they were believed to be formed by recent, flowing water.

[24] [25] [26] [27] Now, new observations suggest that gullies are being made today by chunks of dry ice moving down steep slopes in the spring. [28] [29] [30] [31] [32] [33] [34] [35] As the map below shows gullies and streaks are found in different areas on the planet.

  • Map showing locations of gullies (brown) and streaks (pink)

Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Picture was taken by HiRISE under HiWish program.

Like gullies and streaks, recurring slope lineae are seen on steep slopes, but they are smaller, more narrow, and straighter. Since they seem to lengthen as the temperature increases, they were believed to be involved with liquid water. [36] [37] [38] [39] [40] Nevertheless, later studies showed that very little water, if any, could be involved.[41] [42]

  • Recurrent slop lineae, as seen by HiRISE

References

  1. ↑ Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. Icarus, 205 154–164.
  2. ↑ Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.
  3. ↑ Schorghofer, N.; Aharonson, O.; Khatiwala, S. 2002. Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. Geophys. Res. Lett., 29(23), 2126.
  4. ↑ Chuang, F.C. et al. 2007. HiRISE Observations of Slope Streaks on Mars. Geophys. Res. Lett., 34 L20204.
  5. ↑ Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.
  6. ↑ Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.
  7. ↑ Chuang, F.C.; Beyer, R.A.; Bridges, N.T. 2010. Modification of Martian Slope Streaks by Eolian Processes. Icarus, 205 154–164.
  8. ↑ Baratoux, D. et al. 2006. The Role of the Wind-Transported Dust in Slope Streaks Activity: Evidence from the HRSC Data. Icarus, 183 30–45.
  9. ↑ Morris, E.C. (1982). Aureole Deposits of the Martian Volcano Olympus Mons. J. Geophys. Res., 87(B2), 1164–1178.
  10. ↑ Ferguson,H.M.; Lucchitta, B.K. (1984). Dark Streaks on Talus Slopes, Mars in Reports of the Planetary Geology Program 1983, NASA Tech. Memo., TM-86246, pp. 188–190. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840015363_1984015363.pdf.
  11. ↑ Sullivan, R. et al. (2001). Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.
  12. ↑ Chuang, F.C. et al. 2007. HiRISE Observations of Slope Streaks on Mars. 'Geophys. Res. Lett. 34 L20204.
  13. ↑ Dundas, C. 2018. HIRISE OBSERVATIONS OF NEW MARTIAN SLOPE STREAKS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2026.pdf
  14. ↑ Malin, M.C.; Edgett, K.S. (2001). Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission. J. Geophys. Res., 106(E10), 23,429–23,570.
  15. ↑ Edgett, K.S.; Malin, M.C.; Sullivan, R.J.; Thomas, P.; Veverka, J. (2000). Dynamic Mars: New Dark Slope Streaks Observed on Annual and Decadal Time Scales. 31st Lunar and Planetary Science Conference, Abstract #1058. http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1058.pdf.
  16. ↑ Aharonson, O.; Schorghofer, N.; Gerstell, M.F. (2003). Slope Streak Formation and Dust Deposition Rates on Mars. J. Geophys. Res., 108(E12), 5138, doi:10.1029/2003JE002123.
  17. ↑ Bergonio, J., K. Rottas, and N. Schorghofer. 2013. Properties of martian slope streak populations: 225. Icarus: 194-199.
  18. ↑ Aharonson, O.; Schorghofer, N.; Gerstell, M.F. 2003. S lope Streak Formation and Dust Deposition Rates on Mars. J. Geophys. Res., 108(E12), 5138, doi:10.1029/2003JE002123.
  19. ↑ Schorghofer, Aharonson, O.; Gerstell, M.F.; Tatsumi, L. 2007. Three Decades of Slope Streak Activity on Mars. Icarus: 191, 132–140. doi:10.1016/j.icarus.2007.04.026.
  20. ↑ Treiman, A.H.; Louge, M.Y. (2004). Martian Slope Streaks and Gullies: Origins as Dry Granular Flows. 35th Lunar and Planetary Science Conference, Abstract #1323. http://www.lpi.usra.edu/meetings/lpsc2004/pdf/1323.pdf
  21. ↑ http://www.uahirise.org/epo/nuggets/dust-avalanche.pdf
  22. ↑ https://hirise.lpl.arizona.edu/ESP_054066_1920
  23. ↑ Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar. 2012. Impact air blast triggers dust avalanches on Mars Icarus: 217 (1) 194 doi:10.1016/j.icarus.2011.10.026
  24. ↑ Malin, M.; Edgett, K. (2000). "Evidence for recent groundwater seepage and surface runoff on Mars". Science. 288: 2330–2335.
  25. ↑ Luu, K., et al. 2018. GULLY FORMATION ON THE NORTHWESTERN SLOPE OF PALIKIR CRATER, MARS 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2650.pdf
  26. ↑ Hamid, S., V. Gulick. 2018. GEOMORPHOLOGICAL ANALYSIS OF GULLIES ALONG WESTERN SLOPES OF PALIKIR CRATER. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2644.pdf
  27. ↑ Tyler Paladin, T., et al. 2018. INSIGHTS INTO THE FORMATION OF GULLIES IN ASIMOV CRATER, MARS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2889.pdf
  28. ↑ Dundas, C., S. Diniega, A. McEwen. 2015. Long-term monitoring of martian gully formation and evolution with MRO/HiRISE. Icarus: 251, 244–263
  29. ↑ Fergason, R., C. Dundas, R. Anderson. 2015. IN-DEPTH REGIONAL ASSESSMENT OF THERMOPHYSICAL PROPERTIES OF ACTIVE GULLIES ON MARS. 46th Lunar and Planetary Science Conference. 2009.pdf
  30. ↑ Dundas, C. et al. 2016. HOW WET IS RECENT MARS? INSIGHTS FROM GULLIES AND RSL. 47th Lunar and Planetary Science Conference (2016) 2327.pdf.
  31. ↑ Vincendon, M. 2015. Identification of Mars gully activity types associated with ice composition.JGR:120, 1859–1879.
  32. ↑ Raack, J.; et al. (2015). "Present-day seasonal gully activity in a south polar pit (Sisyphi Cavi) on Mars". Icarus. 251: 226–243. Bibcode:2015Icar..251..226R. doi:10.1016/j.icarus.2014.03.040.
  33. ↑ http://www.uahirise.org/ESP_044327_1375
  34. ↑ C. Pilorget, C., F. Forget. 2015. "CO2 Driven Formation of Gullies on Mars." 46th Lunar and Planetary Science Conference. 2471.pdf
  35. ↑ Pilorget, C.; Forget, F. (2016). "Formation of gullies on Mars by debris flows triggered by CO2 sublimation". Nature Geoscience. 9: 65–69. Bibcode:2016NatGe...9...65P.
  36. ↑ McEwen, A. et al. 2011. Seasonal Flows on Warm Martian Slopes. Science, 333(6043), 740–743. doi:10.1126/science.1204816 PMID 21817049. http://www.sciencemag.org/content/333/6043/740.
  37. ↑ Mann, Adam (18 February 2014). "Strange Dark Streaks on Mars Get More and More Mysterious". Wired. Retrieved 18 February 2014.
  38. ↑ Chang, K. 2011. "Scientists Find Signs Water Is Flowing on Mars," New York Times, August 4, A13. https://www.nytimes.com/2011/08/05/science/space/05mars.html?_r=1&ref=marsplanet.
  39. ↑ HiRISE website. Seasonal Flows on Warm Martian Slopes. http://hirise.lpl.arizona.edu/sim/science-2011-aug-4.php.
  40. ↑ McEwen, A. Ojha L.; Dundas C.; Mattson, S.; Byrne S.; Wray J.; Cull S.; Murchie S. 2011. Transient Slope Lineae: Evidence for Summertime Briny Flows on Mars? 42nd Lunar and Planetary Science Conference, Abstract #2314. http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2314.pdf.
  41. ↑ Dundas, C., et al. 2017. Granular Flows at Recurring Slope Lineae on Mars Indicate a Limited Role for Liquid Water. Nature Geoscience. Nov. 20. [1].
  42. ↑ Schaefer, E., et al. 2018. A case study of recurring slope lineae (RSL) at Tivat crater: Implications for RSL origins. Icarus: In press. https://doi.org/10.1016/j.icarus.2018.07.014

See also

External links

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