[meteorite-list] Detection of Possible Mega-tsunami Deposits on Mars Revives Ancient Ocean Hypothesis

[Ron Baalke]

NEWS RELEASE FROM THE PLANETARY SCIENCE INSTITUTE

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

PSI INFORMATION:

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