Mars' shorelines destroyed by tsunamis
19/05/2016
A study published in Scientific Reports, a publication by the journal Nature, reveals how ancient shorelines of an ocean occupying the plains of northern Mars were destroyed by two mega tsunamis. This new discovery offers a simple answer to the question researchers have had during decades: why are no shorelines visible if there was an ocean on Mars some 3.4 billion years ago?
The research, led by José Alexis Palmero Rodríguez from the Planetary Science Institute (PSI - USA), also included the involvement of researchers from the UAB Department of Geology Mario Zarroca and Rogelio Linares.
The study documented two different tsunamis separated by a period of several million years, during which there was a decrease in ocean levels and the climate became much colder. The tsunamis were caused by the impact of meteorites measuring some 30 km in diameter. The oldest one dragged 10 metre wide boulders and left large extensions of chaotic deposits and excavated channels once the flooding receded; while the second tsunami generated ice-rich lobes (Figure 1).
The shoreline was destroyed by both these events, making it difficult for researchers to recognise it in the studies conducted until now. The analysis of new extremely high resolution images has allowed researchers to identify the characteristic morphologies and deposits of the tsunamis in this new research.
According to the researchers from the Department of Geology, "our results suggest that the waves produced by the tsunamis could have reached heights of 120 metres at the shoreline, penetrating into the continent anywhere from 200 to 700 km. The smooth topography of Mar's northern plains, as well as the particular conditions of wave propagation under much less gravity than that found on Earth, would have made the flooding distances enormous, compared to what can be found on Earth”. (Figure 2)
Researchers highlight the importance of obtaining samples of ice-rich lobes produced by the second tsunami in future space missions. “These materials are relatively close to where the Mars Pathfinder landed. The fact that many of these lobes have highly defined limits and their characteristic morphology is still preserved suggest that there may still be frozen brine from the ancient ocean preserving its primary composition", explains José Alexis Palmero Rodríguez.
The study was conducted with mapping techniques based on the analysis of the images obtained with the cameras CTX and HiRISE (Mars Reconnaissance Orbiter), infrared thermal images with THEMIS (Mars Odyssey) and elevation models with MOLA (Mars Global Surveyor).
Original article J. Alexis P. Rodriguez et al. (including M. Zarroca and R. Linares). "Tsunami Waves Extensively Resurfaced the Shorelines of an Early Martian Ocean." Scientific Reports (Nature Publishing Group) doi:10.1038/srep25106: http://nature.com/articles/doi:10.1038/srep25106
Images:
http://www.uab.cat/uabdivulga/img/UAB_TsunamisMarteFigura1.jpg
Figure 1.-View of a detail of the north-eastern region of Arabia Terra. Image ID: P17_007835_2249_XN_44N349W. This image was taken by the Context Camera (CTX) on board NASA's Mars Reconnaissance Orbiter (MRO) in March 2008. A spectacular Earth analogy of these catastrophes and infrequent ice flows can be observed in this video: https://www.youtube.com/watch?v=OgMBQFf64JM. Upper right margin: Localisation 44.60ºN 10.76ºW, Mars digital elevation model (MOLA). Credits: NASA/USGS/AQUESTA/DLR/FU Berlin G.Neukum.
http://www.uab.cat/uabdivulga/img/UAB_TsunamisMarteFigura2.jpg
Figure 2. - Height and penetration into the continent of the megaflooding caused by a tsunami on the plains of an ancient ocean located in the lowlands of northern Mars, with a wave of 120 metres on the shoreline. Upper left margin: recreation of flooding which could be caused by a similar tsunami on the shores of Barcelona.
