DOCSLIB.ORG

Environmental Effects of Large Impacts on Mars

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Environmental Effects of Large Impacts on Mars R EPORTS Ϫ Ϫ 10 11 year 1) is less than the uncertainty in ly averageduniform surface pressure fieldover the 29. The authors gratefully acknowledge discussions (both the J rate given by (5), confirming that the global ocean. oral andvia e-mail) with J.-P. Boy, D. Bromwich, B. F. 2 18. Because atmospheric pressure trends over Antarctica Chao, Y. Chao, C. M. Cox, M. B. Dyurgerov, L.-L. Fu, M. climatic effects considered here account for are poorly constrained due to a lack of data and Ghil, E. Ivins, K. Mo, andY.Yung, andthe constructive the observed change in J2 slope within the calibration problems (19, 20), we extended the IB comments of the reviewers. The work of J.O.D., uncertainty of the observations. assumption to include the land surface of Antarctica S.L.M., andI.F. presents the results of one phase of In summary, our findings demonstrate in this study. research carriedout at the Jet Propulsion Laboratory, 19. K. M. Hines, D. H. Bromwich, G. J. Marshall, J. Clim. under contract with the National Aeronautics and that the J2 slope reversal observed in 1997– 13, 3940 (2000). Space Administration. O.D.V. is a postdoctoral re- 98 (5) was the result of dramatic changes in 20. G. J. Marshall, J. Clim. 15, 659 (2002). searcher of the National Fundfor Scientific Research, oceanic and glacial mass distribution at that 21. The model bottom pressure is directly proportional Belgium. This work was accomplishedduringO.D.V.’s to the mass-per-unit area above a given point. visit to JPL during Summer 2002. This is a contribu- time. Our modeling results show that an 22. P. Johnston, K. Lambeck, Geophys. J. Int. 136, 537 tion of the ECCO consortium funded by the National equatorward mass shift in the oceans contrib- (1999). Oceanographic Partnership Program. 23. R. Devoti et al., Geophys. Res. Lett. 28, 855 (2001). uted a substantial portion of the J2 increase Supporting Online Material during 1998 (Figs. 1B and 2B; figs. S1 and 24. R. Sabadini, B. L. A. Vermeersen, in Ice Sheets, Sea www.sciencemag.org/cgi/content/full/298/5600/1975/ S2), coincident with phase reversals in both Level and the Dynamic Earth, vol. 29 of Geodynamics DC1 Series, J. X. Mitrovica, B. L. A. Vermeersen, Eds. Materials andMethods ENSO and the PDO. The year 1998 also saw (American Geophysical Union, Washington, DC, SOM Text the warmest global mean surface temperature 2002). Figs. S1 andS2 on record (25), and we found that a concom- 25. J. Hansen et al., J. Geophys. Res. 104, 30,997 (1999). Table S1 26. J. Oerlemans, Ann. Glaciol. 31, 44 (2000). References andNotes itant surge in subpolar glacial melting (13, 27. H. J. Zwally et al., Science 297, 218 (2002). 26) can account for nearly all of the remain- 28. D. Adam, Nature 416, 10 (2002) 27 August 2002; 4 November 2002 ing nonlinear behavior in the J2 observations (Figs. 1C and 2C; Table 1). However, the dynamical links between these relatively rap- id mass shifts and concurrent climate anom- Environmental Effects of Large alies remain to be established. Further knowl- edge of Earth system processes, in particular Impacts on Mars polar ice sheet ablation (27), is needed to form a more comprehensive picture of ongo- Teresa L. Segura,1*† Owen B. Toon,1 AnthonyColaprete, 2 ing mass balance changes and their climatic Kevin Zahnle2 origins. New sources of geodetic data, such as the monthly time-variable gravity fields to The martian valley networks formed near the end of the period of heavy be supplied by the recently launched GRACE bombardment of the inner solar system, about 3.5 billion years ago. The largest mission (28), may soon revolutionize our impacts produced global blankets of very hot ejecta, ranging in thickness from ability to monitor and interpret these changes. meters to hundreds of meters. Our simulations indicated that the ejecta warmed the surface, keeping it above the freezing point of water for periods ranging from decades to millennia, depending on impactor size, and caused References and Notes 1. J. O. Dickey et al., Satellite Gravity and the Geosphere shallow subsurface or polar ice to evaporate or melt. Large impacts also injected (National Research Council, Washington, DC, 1997). steam into the atmosphere from the craters or from water innate to the 2. The definitionandmethodof calculation for J2 are impactors. From all sources, a typical 100-, 200-, or 250-kilometers asteroid in- given in the SOM Text. jected about 2, 9, or 16 meters, respectively, of precipitable water into the at- 3. C. F. Yoder et al., Nature 307, 757 (1983). 4. F. R. Stephenson, L. V. Morrison, Philos. Trans. R. Soc. mosphere, which eventually rained out at a rate of about 2 meters per year. The A 351, 165 (1995). rains from a large impact formed rivers and contributed to recharging aquifers. 5. C. M. Cox, B. F. Chao, Science 297, 831 (2002). 6. A. Cazenave, R. S. Nerem, Science 297, 783 (2002). The valley networks on Mars cut across the ers about 6 ϫ 1025 (4 ϫ 1026,9ϫ 1026)Jof 7. S. R. Hare, N. J. Mantua, Progr. Oceanogr. 47, 103 (2000). heavily cratered southern highlands, the old- energy to the planet and generates a crater 8. T/P andXBT datawere assimilatedinto the model est terrain on the planet, signifying that they ϳ600 (1000, 1300) km in diameter (fig. S1) run starting in 1993. Further details regarding the are contemporaneous with the period of and 3 ϫ 1018 (3 ϫ 1019,5ϫ 1019)kgof ECCO assimilation system are available at www. ecco-group.org. A brief summary is given in the SOM heavy cometary and asteroidal bombardment ejecta (6–8) (Fig. 1). Ejecta include vapor- Text. of Mars and of the rest of the inner solar ized and melted impactor and target materi- 9. E. Rignot, R. H. Thomas, Science 297, 1502 (2002). system (1, 2). There are about 25 visible als. About 20% of the ejecta are rock vapors 10. M. B. Dyurgerov, M. F. Meier, Arct. Alpine Res. 29, 379 craters with diameters between 600 and 4000 (6); most of the rest is melt (7). Only a few (1997). 11. ࿜࿜࿜࿜ , Arct. Alpine Res. 29, 392 (1997). km (fig. S1) (3). Many other large craters percent of the ejecta mass would escape from 12. ࿜࿜࿜࿜ , Proc. Natl. Acad. Sci. U.S.A. 97, 1406 may have been erased by resurfacing events Mars, given a 9 km/s impact velocity (6). In (2000). (4). Here we consider how impacts might the case of large impacts, the ejecta are hot 13. Annual volume changes in subpolar andmountain glaciers were obtainedfrom the NSIDC Web site have caused water to flow on Mars and create because of the large energy release and be- www-nsidc.colorado.edu/sotc/glacier_balance.html, the valley networks. cause of the low surface-to-volume ratio of courtesy of M. Dyurgerov, Institute of Arctic and An asteroid (5) with a diameter of 100 the ejecta, which inhibits cooling. The hot Alpine Research, University of Colorado, Boulder. 14. T. S. James, E. R. Ivins, J. Geophys. Res. 102, 605 (200, 250) km and traveling at 9 km/s deliv- ejecta are distributed globally both ballistical- (1997). ly and via the thermally expanding vapor 15. Glacial contributions to sea level change are not 1Program in Atmospheric andOceanic Sciences, Lab- cloud. For a time, the rock vapor is suspended included in the ocean model, which is constrained to oratory for Atmospheric andSpace Physics, University in the hot atmosphere because it is too warm have constant volume (Boussinesq approximation). of Colorado, Campus Box 392, Boulder, CO 80309– to condense immediately. Before computing the oceanic J2 contribution, the 0392, USA. 2NASA-Ames Research Center, MS 245-3, model bottom pressures are adjusted uniformly such Moffett Field, CA 94035, USA. There are several primary sources of wa- that the global ocean mass is time-invariant. ter. The impactor itself may deliver water. A 16. E. M. Kalnay et al., Bull. Am. Meteorol. Soc. 77, 437 (1996). *Present address: NASA-Ames Research Center, MS 17. The IB assumption accounts for oceanic compensa- 245-3, Moffett Field, CA 94035, USA. 100 (200, 250)-km asteroid that is 5% water tion of atmospheric loading by substituting a spatial- †To whom correspondence should be addressed. by mass (8) would deliver 40 (310, 620) cm www.sciencemag.org SCIENCE VOL 298 6 DECEMBER 2002 1977 R EPORTS of water (global equivalent thickness). The evaporate back into the atmosphere, nor did (Fig. 3). Parts of the martian regolith may be crater is important if the deep regolith of we include the radiative properties of clouds, kept above freezing for at least 2 years, 55 Mars is wet, and as much as 100 (360, 540) but their consideration in our model would years, and 200 years by the 100-, 200-, and cm of water could be liberated from the crater only lengthen the warm periods reported 250-km events, respectively (Fig. 3), and for (9). Because the ejecta are hot, most of this here. millennia for even larger impacts (Fig. 4). water directly enters the atmosphere as vapor. Below the fresh ejecta layer is the original The amount of water precipitated out of the A third possible source is vapor evaporated martian regolith, which we assumed contains atmosphere from vaporization of the impac- from exposed ice, such as the polar caps. If 20% water by mass under a 40-cm dry cap tor, target, and polar caps and melted below this ice were exposed, 30 (250, 500) cm of (14). Permafrost (up to 40% water) and sub- ground for asteroid impactors with different water would be liberated (10) (Fig.
Load more

Recommended publications
  • Interpretations of Gravity Anomalies at Olympus Mons, Mars: Intrusions, Impact Basins, and Troughs
    Lunar and Planetary Science XXXIII (2002) 2024.pdf INTERPRETATIONS OF GRAVITY ANOMALIES AT OLYMPUS MONS, MARS: INTRUSIONS, IMPACT BASINS, AND TROUGHS. P. J. McGovern, Lunar and Planetary Institute, Houston TX 77058-1113, USA, ([email protected]). Summary. New high-resolution gravity and topography We model the response of the lithosphere to topographic loads data from the Mars Global Surveyor (MGS) mission allow a re- via a thin spherical-shell flexure formulation [9, 12], obtain- ¡g examination of compensation and subsurface structure models ing a model Bouguer gravity anomaly ( bÑ ). The resid- ¡g ¡g ¡g bÓ bÑ in the vicinity of Olympus Mons. ual Bouguer anomaly bÖ (equal to - ) can be Introduction. Olympus Mons is a shield volcano of enor- mapped to topographic relief on a subsurface density interface, using a downward-continuation filter [11]. To account for the mous height (> 20 km) and lateral extent (600-800 km), lo- cated northwest of the Tharsis rise. A scarp with height up presence of a buried basin, we expand the topography of a hole Ö h h ¼ ¼ to 10 km defines the base of the edifice. Lobes of material with radius and depth into spherical harmonics iÐÑ up h with blocky to lineated morphology surround the edifice [1-2]. to degree and order 60. We treat iÐÑ as the initial surface re- Such deposits, known as the Olympus Mons aureole deposits lief, which is compensated by initial relief on the crust mantle =´ µh c Ñ c (hereinafter abbreviated as OMAD), are of greatest extent to boundary of magnitude iÐÑ . These interfaces the north and west of the edifice.
    [Show full text]
  • Martian Crater Morphology
    ANALYSIS OF THE DEPTH-DIAMETER RELATIONSHIP OF MARTIAN CRATERS A Capstone Experience Thesis Presented by Jared Howenstine Completion Date: May 2006 Approved By: Professor M. Darby Dyar, Astronomy Professor Christopher Condit, Geology Professor Judith Young, Astronomy Abstract Title: Analysis of the Depth-Diameter Relationship of Martian Craters Author: Jared Howenstine, Astronomy Approved By: Judith Young, Astronomy Approved By: M. Darby Dyar, Astronomy Approved By: Christopher Condit, Geology CE Type: Departmental Honors Project Using a gridded version of maritan topography with the computer program Gridview, this project studied the depth-diameter relationship of martian impact craters. The work encompasses 361 profiles of impacts with diameters larger than 15 kilometers and is a continuation of work that was started at the Lunar and Planetary Institute in Houston, Texas under the guidance of Dr. Walter S. Keifer. Using the most ‘pristine,’ or deepest craters in the data a depth-diameter relationship was determined: d = 0.610D 0.327 , where d is the depth of the crater and D is the diameter of the crater, both in kilometers. This relationship can then be used to estimate the theoretical depth of any impact radius, and therefore can be used to estimate the pristine shape of the crater. With a depth-diameter ratio for a particular crater, the measured depth can then be compared to this theoretical value and an estimate of the amount of material within the crater, or fill, can then be calculated. The data includes 140 named impact craters, 3 basins, and 218 other impacts. The named data encompasses all named impact structures of greater than 100 kilometers in diameter.
    [Show full text]
  • Widespread Crater-Related Pitted Materials on Mars: Further Evidence for the Role of Target Volatiles During the Impact Process ⇑ Livio L
    Icarus 220 (2012) 348–368 Contents lists available at SciVerse ScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus Widespread crater-related pitted materials on Mars: Further evidence for the role of target volatiles during the impact process ⇑ Livio L. Tornabene a, , Gordon R. Osinski a, Alfred S. McEwen b, Joseph M. Boyce c, Veronica J. Bray b, Christy M. Caudill b, John A. Grant d, Christopher W. Hamilton e, Sarah Mattson b, Peter J. Mouginis-Mark c a University of Western Ontario, Centre for Planetary Science and Exploration, Earth Sciences, London, ON, Canada N6A 5B7 b University of Arizona, Lunar and Planetary Lab, Tucson, AZ 85721-0092, USA c University of Hawai’i, Hawai’i Institute of Geophysics and Planetology, Ma¯noa, HI 96822, USA d Smithsonian Institution, Center for Earth and Planetary Studies, Washington, DC 20013-7012, USA e NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA article info abstract Article history: Recently acquired high-resolution images of martian impact craters provide further evidence for the Received 28 August 2011 interaction between subsurface volatiles and the impact cratering process. A densely pitted crater-related Revised 29 April 2012 unit has been identified in images of 204 craters from the Mars Reconnaissance Orbiter. This sample of Accepted 9 May 2012 craters are nearly equally distributed between the two hemispheres, spanning from 53°Sto62°N latitude. Available online 24 May 2012 They range in diameter from 1 to 150 km, and are found at elevations between À5.5 to +5.2 km relative to the martian datum. The pits are polygonal to quasi-circular depressions that often occur in dense clus- Keywords: ters and range in size from 10 m to as large as 3 km.
    [Show full text]
  • 224641234.Pdf
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Helsingin yliopiston digitaalinen arkisto ASTROBIOLOGY Volume 19, Number 3, 2019 Mary Ann Liebert, Inc. DOI: 10.1089/ast.2018.1870 A Low-Diversity Microbiota Inhabits Extreme Terrestrial Basaltic Terrains and Their Fumaroles: Implications for the Exploration of Mars Charles S. Cockell,1 Jesse P. Harrison,2,3 Adam H. Stevens,1 Samuel J. Payler,1 Scott S. Hughes,4 Shannon E. Kobs Nawotniak,4 Allyson L. Brady,5 R.C. Elphic,6 Christopher W. Haberle,7 Alexander Sehlke,6 Kara H. Beaton,8 Andrew F.J. Abercromby,9 Petra Schwendner,1 Jennifer Wadsworth,1 Hanna Landenmark,1 Rosie Cane,1 Andrew W. Dickinson,1 Natasha Nicholson,1 Liam Perera,1 and Darlene S.S. Lim6,10 Abstract A major objective in the exploration of Mars is to test the hypothesis that the planet hosted life. Even in the absence of life, the mapping of habitable and uninhabitable environments is an essential task in developing a complete understanding of the geological and aqueous history of Mars and, as a consequence, understanding what factors caused Earth to take a different trajectory of biological potential. We carried out the aseptic collection of samples and comparison of the bacterial and archaeal communities associated with basaltic fumaroles and rocks of varying weathering states in Hawai‘i to test four hypotheses concerning the diversity of life in these environments. Using high-throughput sequencing, we found that all these materials are inhabited by a low-diversity biota. Multivariate analyses of bacterial community data showed a clear separation between sites that have active fumaroles and other sites that comprised relict fumaroles, unaltered, and syn-emplacement basalts.
    [Show full text]
  • Arxiv:2012.11628V3 [Astro-Ph.EP] 26 Jan 2021
    manuscript submitted to JGR: Planets The Fundamental Connections Between the Solar System and Exoplanetary Science Stephen R. Kane1, Giada N. Arney2, Paul K. Byrne3, Paul A. Dalba1∗, Steven J. Desch4, Jonti Horner5, Noam R. Izenberg6, Kathleen E. Mandt6, Victoria S. Meadows7, Lynnae C. Quick8 1Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA 2Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA 3Planetary Research Group, Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA 4School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA 5Centre for Astrophysics, University of Southern Queensland, Toowoomba, QLD 4350, Australia 6Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA 7Department of Astronomy, University of Washington, Seattle, WA 98195, USA 8Planetary Geology, Geophysics and Geochemistry Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA Key Points: • Exoplanetary science is rapidly expanding towards characterization of atmospheres and interiors. • Planetary science has similarly undergone rapid expansion of understanding plan- etary processes and evolution. • Effective studies of exoplanets require models and in-situ data derived from plan- etary science observations and exploration. arXiv:2012.11628v4 [astro-ph.EP] 8 Aug 2021 ∗NSF Astronomy and Astrophysics Postdoctoral Fellow Corresponding author: Stephen R. Kane, [email protected] {1{ manuscript submitted to JGR: Planets Abstract Over the past several decades, thousands of planets have been discovered outside of our Solar System. These planets exhibit enormous diversity, and their large numbers provide a statistical opportunity to place our Solar System within the broader context of planetary structure, atmospheres, architectures, formation, and evolution.
    [Show full text]
  • Martian Subsurface Properties and Crater Formation Processes Inferred from Fresh Impact Crater Geometries
    Martian Subsurface Properties and Crater Formation Processes Inferred From Fresh Impact Crater Geometries The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Stewart, Sarah T., and Gregory J. Valiant. 2006. Martian subsurface properties and crater formation processes inferred from fresh impact crater geometries. Meteoritics and Planetary Sciences 41: 1509-1537. Published Version http://meteoritics.org/ Citable link http://nrs.harvard.edu/urn-3:HUL.InstRepos:4727301 Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Other Posted Material, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#LAA Meteoritics & Planetary Science 41, Nr 10, 1509–1537 (2006) Abstract available online at http://meteoritics.org Martian subsurface properties and crater formation processes inferred from fresh impact crater geometries Sarah T. STEWART* and Gregory J. VALIANT Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, Massachusetts 02138, USA *Corresponding author. E-mail: [email protected] (Received 22 October 2005; revision accepted 30 June 2006) Abstract–The geometry of simple impact craters reflects the properties of the target materials, and the diverse range of fluidized morphologies observed in Martian ejecta blankets are controlled by the near-surface composition and the climate at the time of impact. Using the Mars Orbiter Laser Altimeter (MOLA) data set, quantitative information about the strength of the upper crust and the dynamics of Martian ejecta blankets may be derived from crater geometry measurements.
    [Show full text]
  • Thermal Infrared Spectroscopy of Explosively Erupted Terrestrial Basalts: Potential Analogues for Surface Compositions on Mars. J
    Lunar and Planetary Science XXXVI (2005) 1114.pdf THERMAL INFRARED SPECTROSCOPY OF EXPLOSIVELY ERUPTED TERRESTRIAL BASALTS: POTENTIAL ANALOGUES FOR SURFACE COMPOSITIONS ON MARS. J. B. Witter1, V. E. Hamilton1 and B. F. Houghton2, 1Hawai'i Institute of Geophysics and Planetology, 2Department of Geology and Geophysics, University of Hawai'i at Manoa, 1680 East West Road, Honolulu, HI 96822; [email protected]. Introduction: Basaltic pyroclastic ejecta from parameters derived from the deposit are: column terrestrial Plinian eruptions may be analogues for height of 50 km and mass eruption rate of ~5 x 108 Martian surface materials observed by the Thermal kg/s [20]. The San Judas Formation resulted from a Emission Spectrometer (TES). We have acquired smaller eruption column (18 km height) and a lower samples from the 122 B.C. Etna (Italy), 1886 Taraw- mass eruption rate (~3 x 107 kg/s) that deposited at era (New Zealand), and prehistoric Masaya (Nicara- least 1.2 km3 of basaltic tephra [20]. The mechanism gua) eruptions for spectral analysis and comparison for Plinian eruption at Masaya is suggested by [19] to to Martian infrared surface spectra. involve rapid ascent of volatile-rich basaltic magma Explosive Basaltic Volcanism on Mars: Nu- from a deep (~100 km) source. merous lines of evidence suggest that explosive ba- 122 B.C. eruption of Etna, Italy. Basaltic pyro- saltic volcanism likely has occurred on Mars clastic deposits at Etna have formed from at least 24 throughout the planet's history. Evidence for explo- sub-Plinian eruptions and one Plinian eruption in the sive activity includes: models of magma ascent and last 13 ka [21].
    [Show full text]
  • Appendix I Lunar and Martian Nomenclature
    APPENDIX I LUNAR AND MARTIAN NOMENCLATURE LUNAR AND MARTIAN NOMENCLATURE A large number of names of craters and other features on the Moon and Mars, were accepted by the IAU General Assemblies X (Moscow, 1958), XI (Berkeley, 1961), XII (Hamburg, 1964), XIV (Brighton, 1970), and XV (Sydney, 1973). The names were suggested by the appropriate IAU Commissions (16 and 17). In particular the Lunar names accepted at the XIVth and XVth General Assemblies were recommended by the 'Working Group on Lunar Nomenclature' under the Chairmanship of Dr D. H. Menzel. The Martian names were suggested by the 'Working Group on Martian Nomenclature' under the Chairmanship of Dr G. de Vaucouleurs. At the XVth General Assembly a new 'Working Group on Planetary System Nomenclature' was formed (Chairman: Dr P. M. Millman) comprising various Task Groups, one for each particular subject. For further references see: [AU Trans. X, 259-263, 1960; XIB, 236-238, 1962; Xlffi, 203-204, 1966; xnffi, 99-105, 1968; XIVB, 63, 129, 139, 1971; Space Sci. Rev. 12, 136-186, 1971. Because at the recent General Assemblies some small changes, or corrections, were made, the complete list of Lunar and Martian Topographic Features is published here. Table 1 Lunar Craters Abbe 58S,174E Balboa 19N,83W Abbot 6N,55E Baldet 54S, 151W Abel 34S,85E Balmer 20S,70E Abul Wafa 2N,ll7E Banachiewicz 5N,80E Adams 32S,69E Banting 26N,16E Aitken 17S,173E Barbier 248, 158E AI-Biruni 18N,93E Barnard 30S,86E Alden 24S, lllE Barringer 29S,151W Aldrin I.4N,22.1E Bartels 24N,90W Alekhin 68S,131W Becquerei
    [Show full text]
  • In Pdf Format
    lós 1877 Mik 88 ge N 18 e N i h 80° 80° 80° ll T 80° re ly a o ndae ma p k Pl m os U has ia n anum Boreu bal e C h o A al m re u c K e o re S O a B Bo l y m p i a U n d Planum Es co e ria a l H y n d s p e U 60° e 60° 60° r b o r e a e 60° l l o C MARS · Korolev a i PHOTOMAP d n a c S Lomono a sov i T a t n M 1:320 000 000 i t V s a Per V s n a s l i l epe a s l i t i t a s B o r e a R u 1 cm = 320 km lkin t i t a s B o r e a a A a A l v s l i F e c b a P u o ss i North a s North s Fo d V s a a F s i e i c a a t ssa l vi o l eo Fo i p l ko R e e r e a o an u s a p t il b s em Stokes M ic s T M T P l Kunowski U 40° on a a 40° 40° a n T 40° e n i O Va a t i a LY VI 19 ll ic KI 76 es a As N M curi N G– ra ras- s Planum Acidalia Colles ier 2 + te .
    [Show full text]
  • The Mars Global Dust Storm of 2018
    49th International Conference on Environmental Systems ICES-2019-181 7-11 July 2019, Boston, Massachusetts The Mars Global Dust Storm of 2018 Michael D. Smith1 and Scott D. Guzewich.1 NASA Goddard Space Flight Center, Greenbelt, MD 20771 Mars is a dusty planet. Wind often lifts dust from the surface into the air forming clouds of dust at different locations across Mars. These dust storms typically last up to a couple days and grow to a few hundred km in size. However, once in a long while when conditions are just right, localized dust storms can interact in a way that optically thick suspended dust covers nearly the entire planet remaining aloft for weeks to months. These global-scale dust storms are the most dramatic of all weather phenomena on Mars, greatly altering the thermal structure and dynamics of the Martian atmosphere and significantly changing the global distribution of surface dust. Such a global-scale dust storm occurred during the summer of 2018, the first such event since 2007. The global dust storm was observed by an international fleet of spacecraft in Mars orbit and on the surface of Mars providing an unprecedented view of the initiation, growth, and decay of the storm as well as the physical properties of the dust during the storm's evolution. The 2018 global-scale dust storm was observed to grow from several localized dust-lifting centers with wind-blown dust suspended in the atmosphere encircling Mars after about two weeks of activity. Dust column optical depths recorded by the Opportunity and Curiosity rovers on the surface were the highest ever recorded on Mars.
    [Show full text]
  • Mars Polar, Ice, and Climate Science: a Summary of Recent Work and Our Current State of Knowledge
    Ninth International Conference on Mars 2019 (LPI Contrib. No. 2089) 6306.pdf MARS POLAR, ICE, AND CLIMATE SCIENCE: A SUMMARY OF RECENT WORK AND OUR CURRENT STATE OF KNOWLEDGE. I. B. Smith,1,2 1York University, Toronto, Ontario, Canada; 2Plane- tary Science Institute Lakewood, Colorado. Contact: [email protected]. Polar and Climate Community activity since the and climate science, already recognized as important 8th Mars conference: Investigations of Mars’ ice and topics for future exploration, but they included active climate have rapidly increased in number and breadth surface processes that have only recently been recog- since the 8th edition of the International Conference on nized for their important role in shaping the surface of Mars was held in 2014. In particular, exciting discover- Mars. Because of this, an entirely new sub-objective ies of mid-latitude ice deposits [1,2] have opened the related to present activity was created under the geolo- door for much more detailed, and creative analysis of gy sub-objective of the goals document. Also, at the permafrost and periglacial terrains [3-7]. At the north spring 2018 36th MEPAG face-to-face meeting, a fo- and south polar layered deposits (NPLD and SPLD), rum of posters highlighted important science and fu- new techniques for stratigraphic studies using high ture investigations, of which polar and climate science resolution stereo [8, 9] and radar [10-12], along with comprised more than half of all submissions [25]. revised surface crater statistics [13] have put more pre- Concurrent to this activity, there have been several cise age constraints on the NPLD.
    [Show full text]
  • Flood-Formed Dunes in Athabasca Valles, Mars: Morphology, Modeling, and Implications
    Icarus 171 (2004) 68–83 www.elsevier.com/locate/icarus Flood-formed dunes in Athabasca Valles, Mars: morphology, modeling, and implications Devon M. Burr a,∗,PaulA.Carlingb,RossA.Beyerc, Nicholas Lancaster d,1 a USGS Astrogeology Branch, 2255 N. Gemini Dr., Flagstaff, AZ 86001, USA b School of Geography, University of Southampton, Highfield, Southampton SO17 1BJ, UK c Department of Planetary Sciences, The University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, USA d Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA Received 2 December 2003; revised 6 April 2004 Available online 11 June 2004 Abstract Estimates of discharge for martian outflow channels have spanned orders of magnitude due in part to uncertainties in floodwater height. A methodology of estimating discharge based on bedforms would reduce some of this uncertainty. Such a methodology based on the mor- phology and granulometry of flood-formed (‘diluvial’) dunes has been developed by Carling (1996b, in: Branson, J., Brown, A.G., Gregory, K.J. (Eds.), Global Continental Changes: The Context of Palaeohydrology. Geological Society Special Publication No. 115, London, UK, 165–179) and applied to Pleistocene flood-formed dunes in Siberia. Transverse periodic dune-like bedforms in Athabasca Valles, Mars, have previously been classified both as flood-formed dunes and as antidunes. Either interpretation is important, as they both imply substantial quantities of water, but each has different hydraulic implications. We undertook photoclinometric measurements of these forms, and com- pared them with data from flood-formed dunes in Siberia. Our analysis of those data shows their morphology to be more consistent with dunes than antidunes, thus providing the first documentation of flood-formed dunes on Mars.
    [Show full text]