[meteorite-list] Study Indicates An Ancient Ocean May Have Covered One-third of Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 14 Jun 2010 13:38:05 -0700 (PDT)
Message-ID: <201006142038.o5EKc5B1012709_at_zagami.jpl.nasa.gov>

June 13, 2010

Media Contact:
Jim Scott
+1 303-492-3114
jim.scott at colorado.edu

Science Contacts:
Gaetano Di Achille
gaetano.diachille at lasp.colorado.edu

Brian Hynek
+1 303-735-4312
brian.hynek at colorado.edu

NEW CU-BOULDER STUDY INDICATES AN ANCIENT
OCEAN MAY HAVE COVERED ONE-THIRD OF MARS

A vast ocean likely covered one-third of the surface of Mars some 3.5
billion years ago, according to a new study conducted by University of
Colorado at Boulder scientists.

The CU-Boulder study is the first to combine the analysis of
water-related features including scores of delta deposits and
thousands of river valleys to test for the occurrence of an ocean
sustained by a global hydrosphere on early Mars. While the notion of a
large, ancient ocean on Mars has been repeatedly proposed and
challenged over the past two decades, the new study provides further
support for the idea of a sustained sea on the Red Planet during the
Noachian era more than 3 billion years ago, said CU-Boulder researcher
Gaetano Di Achille, lead author on the study.

A paper on the subject authored by Di Achille and CU-Boulder Assistant
Professor Brian Hynek of the geological sciences department appears in
the June 13 issue of Nature Geoscience. Both Di Achille and Hynek are
affiliated with CU-Boulder's Laboratory for Atmospheric and Space
Physics.

More than half of the 52 river delta deposits identified by the CU
researchers in the new study -- each of which was fed by numerous
river valleys -- likely marked the boundaries of the proposed ocean,
since all were at about the same elevation. Twenty-nine of the 52
deltas were connected either to the ancient Mars ocean or to the
groundwater table of the ocean and to several large, adjace
Di Achille said.

The study is the first to integrate multiple data sets of deltas,
valley networks and topography from a cadre of NASA and European Space
Agency orbiting missions of Mars dating back to 2001, said Hynek. The
study implies that ancient Mars probably had an Earth-like global
hydrological cycle, including precipitation, runoff, cloud formation,
and ice and groundwater accumulation, Hynek said.

Di Achille and Hynek used a geographic information system, or GIS, to
map the Martian terrain and conclude the ocean likely would have
covered about 36 percent of the planet and contained about 30 million
cubic miles, or 124 million cubic kilometers, of water. The amount of
water in the ancient ocean would have formed the equivalent of a
1,800-foot, or 550-meter-deep layer of water spread out over the
entire planet.

The volume of the ancient Mars ocean would have been about 10 times
less than the current volume of Earth's oceans, Hynek said. Mars is
slightly more than half the size of Earth.

The average elevation of the deltas on the edges of the proposed ocean
was remarkably consistent around the whole planet, said Di Achille. In
addition, the large, ancient lakes upslope from the ancient Mars ocean
likely formed inside impact craters and would have been filled by the
transport of groundwater between the lakes and the ancient sea,
according to the researchers.

A second study headed by Hynek and involving CU-Boulder researcher
Michael Beach of LASP and CU-Boulder doctoral student Monica Hoke
being published in the Journal of Geophysical Research-Planets --
which is a publication of the American Geophysical Union -- detected
roughly 40,000 river valleys on Mars. That is about four times the
number of river valleys that have previously been identified by
scientists, said Hynek.

The river valleys were the source of the sediment that was carried
downstream and dumped into the deltas adjacent to the proposed ocean,
said Hynek. "The abundance of these river valleys require
significant amount of precipitation," he said. "This effectively puts
a nail in the coffin regarding the presence of past rainfall on Mars."
Hynek said an ocean was likely required for the sustained
precipitation.

"Collectively, these results support the existing theories regarding
the extent and formation time of an ancient ocean on Mars and imply
the surface conditions during the time probably allowed the occurrence
of a global and active hydrosphere integrating valley networks, deltas
and a vast ocean as major components of an Earth-like hydrologic
cycle," Di Achille and Hynek wrote in Nature Geoscience.

"One of the main questions we would like to answer is where all of the
water on Mars went," said Di Achille. He said future Mars missions --
including NASA's $485 million Mars Atmosphere and Volatile Evolution
mission, or MAVEN, which is being led by CU-Boulder and is slated to
launch in 2013 -- should help to answer such questions and provide new
insights into the history of Martian water.

The river deltas on Mars are of high interest to planetary scientists
because deltas on Earth rapidly bury organic carbon and other
biomarkers of life and are a prime target for future exploration. Most
astrobiologists believe any present indications of life on Mars will
be discovered in the form of subterranean microorganisms.

"On Earth, deltas and lakes are excellent collectors and preservers of
signs of past life," said Di Achille. "If life ever arose on Mars,
deltas may be the key to unlocking Mars' biological past."

Hynek said long-lived oceans may have provided an environment for
microbial life to take hold on Mars.

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The study was funded by NASA's Mars Data Analysis Program.
Received on Mon 14 Jun 2010 04:38:05 PM PDT