Geologically recent glacial melting on Mars

Post by Frances. E. G. Butcher, School of Physical Sciences, Open University, UK.

Thousands of putative debris-covered glaciers in Mars’ middle latitudes host water ice in volumes comparable to that of all glaciers and ice caps on Earth, excluding the Greenland and Antarctic ice sheets (Levy et al., 2014). These glaciers formed within the last 100 million to 1 billion years of Mars’ geological history (Berman et al., 2015), a period that is thought to have been similarly cold and hyper-arid to present-day Mars. This is broadly corroborated by a sparsity of evidence for melting of these geologically ‘young’ mid-latitude glaciers, which suggests that they have always been entirely frozen to their beds in ‘cold-based’ thermal regimes, and haven’t generated meltwater (e.g. Marchant and Head, 2007). Nevertheless, this months’ planetary geomorphology image provides evidence for melting of one such glacier.


Image 1: An esker emerging from the tongue of a debris-covered glacier in Tempe Terra, Mars. See Image 2 for an annotated 3D view of this scene. The dashed white line delineates the terminus of the debris-covered glacier, which occupies the southern and eastern portions of the image. The white arrow marked A indicates the first emergence of the crest of the esker ridge from the glacier surface. The white arrow marked A’ indicates the northernmost end of the esker ridge in the deglaciated zone beyond the ice terminus. Context Camera image P05_002907_2258_XN_45N083W (Malin et al., 2007). Modified from Butcher et al., 2017 under a Creative Commons license CC BY 4.0.



Image 2: A 3D oblique view from the south west corner of the scene in Image 1, with key features highlighted. The surface of the debris-covered glacier, which terminates at the white dashed line, is highlighted in blue. The esker, which is ~14 km long, and 5-55 m high, is highlighted in pink. The glacier has thinned and its surface lowered to reveal portions of the crest of the esker within the lower glacier tongue. The esker crest first emerges from the glacier surface 7 km up-glacier of the ice terminus, and it extends a further 7 km beyond the ice terminus into the deglaciated glacier foreland. The base image is a shaded-relief map draped on a 3D model of the scene (with 5 times vertical exaggeration) that was generated from High Resolution Imaging Science Experiment images ESP_049573_2265 and ESP_049639_2265 (McEwen et al., 2007). Modified from Butcher et al., 2017 under a Creative Commons license CC BY 4.0.

Image 1 shows a recently-discovered ‘esker’ emerging from the tongue of an existing (~110 million year-old) debris-covered glacier in the Tempe Terra region of Mars’ northern mid-latitudes (Butcher et al., 2017). Image 2 shows an annotated oblique 3D view of the same feature as Image 1. Eskers are snake-like ridges of sediment deposited by glacial meltwater as it flows through drainage tunnels within glacial ice (e.g. Perkins et al., 2016). As their parent glacier retreats, esker ridges are left in the landscape as sinuous ridges tracing the former glacial plumbing system. An esker deposited by the Breiðamerkurjökull glacier (southeast Iceland) is shown in Image 3. Identification of an esker associated with an existing mid-latitude glacier on Mars indicates past melting of that glacier, and challenges the concept that the most recent phase of glaciation of Mars’ mid-latitudes was perennially and ubiquitously cold-based (Butcher et al., 2017).


Image 3: An esker in the foreland of the Breiðamerkurjökull glacier in southeast Iceland. The terminus of Breiðamerkurjökull has retreated 3 km to the north west since the esker was deposited. DigitalGlobe image from Google Earth centered on the coordinates 64°03’16.06″ N 16°19’06.07″ W.

The glacier-linked esker on Mars is located within a tectonic rift valley which formed as Mars’ crust was stretched by the growth of the large Martian volcanoes (Hauber et al., 2010). The only other glacier-linked esker identified on Mars to date* is also located within a similar tectonic rift valley, in the Phlegra Montes region of Mars’ northern mid-latitudes (Gallagher and Balme, 2015). Image 4 shows a comparison of the locations of these extremely rare glacier-linked eskers. The similarity of these settings suggests that a genetic link may exist between the tectonic rift valleys and the melt events that allowed glaciers to deposit eskers within them (Gallagher and Balme, 2015; Butcher et al., 2017). Tectonic rift valleys on Earth are commonly associated with elevated geothermal heat flux (heat provided from within the ground; e.g. Jordan et al., 2010). Above-average geothermal heat in the tectonic rifts on Mars may have provided an essential heat source to melt the beds of the glaciers that occupy them, and permit esker deposition, despite the extremely cold climates that have prevailed throughout Mars’ most recent geological period (Gallagher and Balme, 2015; Butcher et al., 2017).

*The glacier-linked esker identified by Gallagher and Balme (2015) was the subject of a previous IAG Planetary Geomorphology Image of the Month post, available here.


Image 4: Colourized elevation maps from the Mars Orbiter Laser Altimeter (MOLA; Smith et al., 2001) overlain on Thermal Emission Imaging System daytime infrared images (Christensen et al., 2004; Edwards et al., 2011), showing the locations of the glacier-linked eskers (white dots) in (a) a rift valley in the Tempe Terra region (Butcher et al. 2017) and (b) a rift valley in the Phlegra Montes region (Gallagher and Balme, 2015). The black box in (a) shows the extent of Image 1. Modified from Butcher et al., 2017 under a Creative Commons license CC BY 4.0.


Further Reading

Levy, J. S., Fassett, C. I., Head, J. W., Schwartz, C., & Watters, J. L. (2014). Sequestered glacial ice contribution to the global Martian water budget: Geometric constraints on the volume of remnant, mid-latitude debris-covered glaciers. Journal of Geophysical Research: Planets, 119, 2188–2196.

Berman, D.C., Crown, D.A., & Joseph, E.C.S. (2015). Formation and mantling ages of lobate debris aprons on Mars: Insights from categorized crater counts. Planetary and Space Science, 111, 83-99.

Marchant, D. R., & Head, J. W. (2007). Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climate change on Mars. Icarus, 192(1), 187–222.

Perkins, A. J., Brennand, T. A., & Burke, M. J. (2016). Towards a morphogenetic classification of eskers: Implications for modelling ice sheet hydrology. Quaternary Science Reviews, 134, 19–38.

Butcher, F. E. G., Balme, M. R., Gallagher, C., Arnold, N. S., Conway, S. J., Hagermann, A., & Lewis, S. R. (2017).Recent basal melting of a mid-latitude glacier on Mars. Journal of Geophysical Research: Planets, 122.

Hauber, E., Grott, M., & Kronberg, P. (2010). Martian rifts: Structural geology and geophysics. Earth and Planetary Science Letters, 294(3-4), 393–410.

Gallagher, C., & Balme, M. (2015). Eskers in a complete, wet-based glacial system in the Phlegra Montes region, Mars. Earth and Planetary Science Letters, 431, 96–109.

Jordan, T. A., Ferraccioli, F., Vaughan, D. G., Holt, J. W., Corr, H., Blankenship, D. D., & Diehl, T. M. (2010). Aerogravity evidence for major crustal thinning under the Pine Island Glacier region (West Antarctica). GSA Bulletin, 122(5-6), 714–726.

Malin, M. C., Bell, J. F., Cantor, B. A., Caplinger, M. A., Calvin, W. M., Clancy, R. T.,…Wolff, M. J. (2007). Context Camera investigation on board the Mars Reconnaissance Orbiter. Journal of Geophysical Research, 112, E05S04.

McEwen, A. S., Eliason, E. M., Bergstrom, J. W., Bridges, N. T., Hansen, C. J., Delamere, W. A.,…Weitz, C. M. (2007). Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE). Journal of Geophysical Research, 112, E05S02.

Smith, D. E., Zuber, M. T., Frey, H. V., Garvin, J. B., Head, J. W., Muhleman, D. O., … Sun, X. (2001). Mars Orbiter Laser Altimeter: Experiment summary after the first year of global mapping of Mars. Journal of Geophysical Research, 106(E10), 23689–23722.

Christensen, P. R., Jakosky, B. M., Kieffer, H. H., Malin, M. C., McSween, H. Y. Jr., Nealson, K.,…Ravine, M. (2004). The Thermal Emission Imaging System (THEMIS) for the Mars 2001 Odyssey mission. Space Science Reviews, 110(1/2), 85–130.

Edwards, C. S., Nowicki, K. J., Christensen, P. R., Hill, J., Gorelick, N., & Murray, K. (2011). Mosaicking of global planetary image datasets: 1. Techniques and data processing for Thermal Emission Imaging System (THEMIS) multi-spectral data. Journal of Geophysical Research, 116, E10008.

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