Research ArticlePLANETARY SCIENCE

Persistence of intense, climate-driven runoff late in Mars history

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Science Advances  27 Mar 2019:
Vol. 5, no. 3, eaav7710
DOI: 10.1126/sciadv.aav7710
  • Fig. 1 Global distribution of data.

    Most of our data are for post–3.4 Ga rivers. Width (A) and wavelength (B) measurements. Some measurements are too close-spaced to be distinguished at this scale. We use k-means clustering of spatial locations of the data (see the Supplementary Materials) to identify 10 distinct groups, labeled 1 through 10. Each group is represented by circles of varying colors. Location of the Mars Science Laboratory (MSL) rover shown for reference. For comparison, the gray dots show the location of (mostly pre–3.4 Ga) valleys mapped by (11). The background is Mars Orbiter Laser Altimeter topography, clipped at elevations of −6 km (blue) and 8 km (red).

  • Fig. 2 Mars paleo-river dimensions.

    (A) River width comparison for ancient Mars versus modern Earth. Mars data are shown using colored symbols (blue squares, negative relief channels; orange circles, inverted relief channels). The thick black line is the best fit to all Mars data, and the thick orange line is the best fit to Mars inverted relief channel widths. Only the widest channel for each catchment area is shown. The gray-shaded region corresponds to the channel widths expected based on the best-fit to meander wavelengths 0.0625 × to 0.125 × wavelength (19). Earth data (25) are shown as black dots, and the best fit to Earth data are shown by the thin dashed line. (B) Mars sinuous channel wavelengths. Color of dots corresponds to sinuosity. The thick black line shows the fit to all data. The thin black line shows the fit to the most sinuous channels (sinuosity >1.5).

  • Fig. 3 Paleodischarge estimates.

    Filled symbols are width-based discharge estimates using an empirical scaling. Blue squares, negative relief channels; orange circles, inverted relief channels. Open diamonds are meander-wavelength based discharge estimates, using an empirical scaling (error bars not shown). The blue dashed lines show runoff production, R. The black line shows the fit to the width data, the orange line shows the fit to the inverted relief channels only, and the green line shows the fit to the sinuous-channel wavelength data. The gray band shows the fit to the data re-estimated using a scaling that is strongly dependent on grain size for D50 ≈ 0.0625 to 0.125 m (34). The gray dashed lines show fits to the width data for the extremes of the range of D50 considered, D50 = 0.01 to 0.5 m. All wavelengths are shown, but only the largest widths in each catchment are shown. The bootstrap errors on the fits are small and are not shown.

  • Fig. 4 Improved Mars paleoclimate model constraints via paleodischarge estimates from global database of paleo-rivers and river deposits.

    Results for all data are shown (not just the largest in each catchment). Additional energy generates runoff. Purple shading: width-based estimates, threshold channel method (τ = τcr); red shading: width-based estimates (empirical scaling); black line: meander-based estimates (empirical scaling). Because of geologic noise [e.g., (14)], the central estimate from the histograms (not the extremum) should be taken as the constraint for climate models.

  • Fig. 5 A new geologic history of Mars’ river runoff.

    (A) Our data are evidence that high rates of peak runoff production, and thus high peak rates of landscape erosion via fluvial sediment transport, were sustained after 3.4 Ga ago. The gray patches correspond to the catchment-to-catchment SD of the estimated runoff production, and the black bars correspond to the bootstrapped 2σ Poisson error for mean runoff production. The leftmost bar corresponds to results previously reported in (15). The central bar corresponds to our data for Late Hesperian/Early Amazonian terrains (with “highlands” measurements excluded; n = 149). The rightmost bar corresponds to our data for the (likely ice-rich) Middle Amazonian stippled mantling unit of Lyot crater (region 8 in Fig. 1; n = 16) (41). For our data, only the largest channels for each catchment are included. All data are corrected for the area dependence in runoff production seen in Fig. 3 (see fig. S7 for the uncorrected data). The offset between Earth’s runoff production (blue symbol) and Mars’ runoff production is sensitive to the assumed grain size (Figs. 3 and 4). (B) Summary of fluvial climates on Mars, informed by our results. Gray shading in upper quarter-circle plots corresponds to the spatial density of rivers (darker shading = higher spatial density).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/3/eaav7710/DC1

    Fig. S1. Examples of traces showing preservation quality.

    Fig. S2. Details of method.

    Fig. S3. Paleo-river slope data.

    Fig. S4. Sensitivity tests.

    Fig. S5. Discharge area scaling: Relationship between catchment-averaged runoff production, R, and drainage area, A.

    Fig. S6. Regional variations in estimated runoff production.

    Fig. S7. Geologic history of Mars’ river runoff.

    Fig. S8. Width-discharge relationships from terrestrial fieldwork and laboratory experiments.

    Table S1. Table of DTMs.

    Table S2. Geologic settings of study sites.

    References (4952)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Examples of traces showing preservation quality.
    • Fig. S2. Details of method.
    • Fig. S3. Paleo-river slope data.
    • Fig. S4. Sensitivity tests.
    • Fig. S5. Discharge area scaling: Relationship between catchment-averaged runoff production, R, and drainage area, A.
    • Fig. S6. Regional variations in estimated runoff production.
    • Fig. S7. Geologic history of Mars’ river runoff.
    • Fig. S8. Width-discharge relationships from terrestrial fieldwork and laboratory experiments.
    • Table S1. Table of DTMs.
    • Table S2. Geologic settings of study sites.
    • References (4952)

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