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NEWS RELEASE FROM THE PLANETARY SCIENCE INSTITUTE

FROM:
Alan Fischer
Public Information Officer
Planetary Science Institute
520-382-0411
520-622-6300
fischer@psi.edu

Detection of Possible Mega-tsunami Deposits on Mars Revives Ancient Ocean Hypothesis

May 19, 2016, Tucson, Ariz. - New geologic mapping in the Martian northern plains reveals vast sedimentary deposits that were likely emplaced by
two mega-tsunamis, according to a new paper in Nature Scientific Reports
led by Planetary Science Institute Senior Scientist J. Alexis Palmero Rodriguez.

The proposed tsunami events had onshore wave heights that likely reached
as high as 120 meters and moved several hundred kilometers inland.

"For more than a quarter century, failure to identify shoreline features consistently distributed along a constant elevation has been regarded
as inconsistent with the hypothesis that a vast ocean existed on Mars approximately 3.4 billion years ago. Our discovery offers a simple solution to this problem; widespread tsunami deposits distributed within a wide
range of elevations likely characterize the shorelines of early Martian oceans," Rodriguez said.

"The tsunamis could have been triggered by bolide impacts, which about
every 3 million years, generated marine impact craters approximately 30 kilometers in diameter. Thus, the proposed tsunami events likely took
place a few millions years apart," said PSI Research Scientist and co-author Thomas Platz.

Mega-tsunamis also form on Earth, and their deposits, too, show tremendous variability in their topographic distribution and inundation distances. However, these are extremely rare and catastrophic events, and consequentially their deposits are mostly obscured - or removed - by younger resurfacing processes.

"During the time period that separated the two tsunami events the ocean
level receded to form a lower shoreline and the climate became significantly colder. Evidence for climate change is reflected in the morphology of
the tsunami deposits. The older tsunami emplaced enormous boulder-rich deposits and as the wave retreated back into the ocean it formed widespread backwash channels," Rodriguez said.

In contrast, the younger tsunami emplaced lobes that are primarily made
of water-ice, he said. Sampling of these materials by future Landers is
of particular scientific importance because they likely consist of frozen ancient ocean water brines. Furthermore, these materials are in relatively close proximity to the Mars Pathfinder landing site, demonstrating possible accessibility with current and tested technologies.

The vast areas covered by these ice-rich lobes imply that the frozen remnants of early Mars ocean water might be widespread not just rare and localized occurrences. The fact that many of the lobes have well-defined boundaries
and that their flow-related-shapes are not significantly modified suggest
that they might still retain much of the originally emplaced materials,
which could be informative of the oceanAs primary composition.

"In spite of the extremely cold and dry global climatic conditions, the
early Martian ocean likely had a briny composition that allowed it to
remain in liquid form for as long as several tens of millions of years. Subfreezing briny aqueous environments are known to be habitable environments on Earth, and consequently, some of the tsunami deposits might be prime astrobiological targets," said co-author Alberto Fairen, a research scientist at the Center for Astrobiology in Spain, and a visiting scientist in Cornell University's Department of Astronomy.

"Yet this large expanse of currently documented tsunami inundation is
but a portion of what occurred along the margin of the Martian northern plains-filling ocean. Tsunami-related features along other parts of the
ocean margin, and potentially other smaller former bodies of water, remain
to be identified, mapped and studied in detail," said co-author Kenneth
Tanaka of the U.S. Geological Survey.

"We have already identified some areas inundated by the tsunamis where
the ponded water appears to have emplaced lacustrine sediments, including evaporites. As a follow-up investigation we plan to characterize these terrains and assess their potential for future robotic or human in-situ exploration," Rodriguez said.

Visit http://www.psi.edu/news/tsunamimars for illustrations related to
the research.

Rodriguez and co-author Jianguo Yan of Wuhan University are currently
planning an expedition to Tibet to investigate high mountain lakes, in
which they have identified landforms developed under extreme environmental conditions that comprise outstanding analogs to features indentified within the possible tsunami-generated paleo-lakes.


CONTACT:

J. Alexis Palmero Rodriguez
Senior Scientist
650-450-7352
alexis@psi.edu

PSI INFORMATION:

Mark V. Sykes
Director
520-622-6300
sykes@psi.edu

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