The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground1,2,3; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth.
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Malin, M. C. & Edgett, K. S. Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission. J. Geophys. Res. 106, 23429–23570 (2001)
Cantor, B., Malin, M. & Edgett, K. S. Multiyear Mars Orbiter Camera (MOC) observations of repeated Martian weather phenomena during the northern summer season. J. Geophys. Res. 107, doi:10.1029/2001JE001588 (2002)
Edgett, K. S., Supulver, K. D. & Malin, M. C. Spring defrosting of martian polar regions: Mars Global Surveyor MOC and TES monitoring of the Richardson crater dune field, 1999–2000. In 2nd International Conference on Mars Polar Science and Exploration (University of Iceland, Reykjavik, 21–25 August 2000) 34 (Univ. Iceland, Reykjavik, 2000).
Kieffer, H. H., Titus, T., Mullins, K. & Christensen, P. R. Mars south polar cap behaviour observed by TES: Seasonal cap evolution controlled by frost grain size. J. Geophys. Res. 105, 9653–9700 (2000)
Malin, M. C. & Edgett, K. S. Early defrosting of the 1999 south polar seasonal frost cap: Evidence of interannual climate change? Lunar Planet. Sci. [CD-ROM] XXXI, abstr. 1052 (2000)
Kieffer, H. H. Annual punctuated CO2 slab-ice and jets on Mars. In 2nd International Conference on Mars Polar Science and Exploration (University of Iceland, Reykjavik, 21–25 August 2000) 93 (Univ. Iceland, Reykjavik, 2000).
Piqueux, S., Byrne, S. & Richardson, M. I. Sublimation of Mars's southern seasonal CO2 cap and the formation of spiders. J. Geophys. Res. 108, 5084, doi:10.1029/2002JE002007 (2003)
Supulver, K. D., Edgett, K. S. & Malin, M. C. Seasonal changes in frost cover in the martian south polar regions: Mars Global Surveyor MOC and TES monitoring of the Richardson Crater dune field. Lunar Planet. Sci. XXXII, abstr. 1966 (2001)
Kossacki, K. J. & Leliwa-Kopystynski, J. Non-uniform seasonal defrosting of subpolar dune field on Mars. Icarus 168, 201–204 (2004)
Christensen, P. R. et al. The Thermal Emission Imaging System (THEMIS) for the Mars 2001 Odyssey Mission. Space Sci. Rev. 110, 85–130 (2004)
Christensen, P. R. et al. Morphology and composition of the surface of Mars: Mars Odyssey THEMIS results. Science 300, 2056–2061 (2003)
Christensen, P. R., Gorelick, N. S., Mehall, G. L. & Murray, K. C. THEMIS Public Data Releases. Planetary Data System node. http://themis-data.asu.edu (Arizona State Univ., Tempe, Arizona, 2006).
Christensen, P. R., Kieffer, H. H. & Titus, T. Infrared and visible observations of south polar spots and fans. Eos (Fall Meeting Suppl.) 86(52), abstr. P23C–04 (2005)
Titus, T. N., Kieffer, H. H. & Christensen, P. R. Exposed water ice discovered near the south pole of Mars. Science 299, 1048–1051 (2003)
Smith, D. E., Zuber, M. T. & Neumann, G. A. Seasonal variations of snow depth on Mars. Science 294, 2141–2146 (2001)
Feldman, W. C. et al. CO2 frost cap thickness on Mars during northern winter and spring. J. Geophys. Res. 108, 5103, doi:I0.1029/2003JE002101 (2003)
Boynton, W. V. et al. Distribution of hydrogen in the near surface of Mars: Evidence for subsurface ice deposits. Science 297, 81–85 (2002)
Titus, T. N., Kieffer, H. H., Mullins, K. F. & Christensen, P. R. TES Pre-mapping data: Slab ice and snow flurries in the Martian north polar night. J. Geophys. Res. 106, 23181–23196 (2001)
Kieffer, H. H. Behaviour of solid CO2 on Mars: A real zoo. 6th Int. Conf. Mars (Pasadena, California, 20–25 July 2003) abstr. 3158 (California Institute of Technology, Pasadena, 2003).
Kieffer, H. H. & Titus, T. N. TES mapping of Mars' north seasonal cap. Icarus 154, 162–189 (2001)
Mitrofanov, I. G. et al. CO2 snow depth and subsurface water-ice abundance in the northern hemisphere of Mars. Science 27, 2081–2084 (2003)
Haberle, R. M., Mattingly, B. & Titus, T. N. Reconciling different observations of CO2 ice mass loading of the martian north polar cap. Geophys. Res. Lett. 31, L05702, doi:10.1029/2004GL019445 (2004)
Langevin, Y. et al. No signature of clear CO2 ice from the ‘cryptic’ regions in Mars' south seasonal polar cap. Nature doi:10.1038/nature05012 (this issue)
Kieffer, H. H. Interpretation of the martian polar cap spectra. J. Geophys. Res. 75, 510–514 (1970)
Bibring, J.-P. et al. Perennial water ice identified in the south polar cap of Mars. Nature 428, 627–630 (2004)
Soderblom, L. A. et al. Triton's geyser-like plumes—Discovery and basic characterization. Science 250, 410–415 (1990)
Kirk, R. L., Soderblom, L. A. & Brown, R. H. Subsurface energy storage and transport for solar-powered geysers on Triton. Science 250, 424–429 (1990)
Christensen, P. R. et al. The Mars Global Surveyor Thermal Emission Spectrometer experiment: Investigation description and surface science results. J. Geophys. Res. 106, 23823–23871 (2001)
We thank the members of the Odyssey and THEMIS mission teams and the ASU and USGS software development group for their efforts in obtaining and processing the THEMIS data used in this work.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
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Kieffer, H., Christensen, P. & Titus, T. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature 442, 793–796 (2006). https://doi.org/10.1038/nature04945
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