Spacecraft observations of the landing area for one of NASA’s two
Mars rovers now indicate there likely was an enormous sea or lake
covering the region in the past, according to a new University of
Colorado at Boulder study.

Research Associate Brian Hynek of the Laboratory for Atmospheric and
Space Physics said data from the Mars Global Surveyor and Mars
Odyssey spacecraft now show that the region surrounding the
Opportunity rover’s landing site probably had a body of water at
least 330,000 square kilometers, or 127,000 square miles. That would
make the ancient sea larger in surface area than all the Great Lakes
combined, or comparable to Europe’s Baltic Sea.

In March, Opportunity instruments scanning the Meridiani Planum
landing region confirmed that rock outcrops there, rich in the iron
oxide mineral hematite, also contained the types of sulfate that only
could have been created by interactions of water with Martian rock.
Hynek used thermal emission data and camera images from the orbiting
spacecraft to show such bedrock outcrops extend outward for many
miles north, east and west.

“If the outcrops are a result of sea deposition, the amount of water
once present must have been comparable to the Baltic Sea or all of
the Great Lakes combined,” he said. Hynek speculated that future
studies may show that the ancient sea was even larger.

A paper on the subject by Hynek appears in the Sept. 9 issue of Nature.

The thermal emission imaging system, or THEMIS, aboard Mars Odyssey
is used to infer the particle size of rocks near or on the surface of
Mars, he said.

High thermal inertia measurements indicate a prevalence of larger
chunks of rock, which heat up more slowly in daylight and cool more
slowly in evenings. Low thermal inertia measurements are from
fine-grained particles that heat and cool more quickly.

The thermal maps of Mars developed by Hynek indicate the rocky
outcrops associated with ancient water extend far outside the
boundaries of the landing area. “The thermal inertia for this area
is relatively high, an indication the region contains substantial
bedrock,” he said.

Hynek speculated that if the outcrops at the landing site are the
result of sea deposition, as believed, the body of water must have
been deep enough and persisted long enough to build up sediments
roughly one-third of a mile deep. “For this to occur, the ancient
global climate of Mars must have been different from its present
climate and have lasted for an extended period,” Hynek wrote in the
Nature paper.

“I believe new findings showing evidence of large amounts of water on
Mars over long periods of time could increase the science potential
for those seeking evidence of past or present life on Mars,” said
Hynek.

Hematite deposits on Earth come primarily from the presence of
long-standing water or groundwater systems, Hynek said. Many
scientists believe the requirement for primitive life forms, at least
on Earth, include water or some other liquid, a source of energy and
access to elements to construct complex molecules.

“It is important to understand how extensive these water-rich
environments were and how long they persisted, because life required
at least some degree of environmental stability in order to begin and
to evolve,” said NASA-Ames Research Center astrobiologist David Des
Marais regarding Hynek’s study.

“Orbital observations and future landed missions will provide crucial
details about the long-term legacy of liquid water on Mars, and
whether life ever became a part of that legacy,” said Des Marais, a
member of the Mars rover science team.

CU-Boulder doctoral student Nathaniel Putzig and LASP Research
Associate Michael Mellon assisted in the data processing for the
remote sensing images used in the Nature study.

The Mars rover, Spirit, landed in the Gusev Crater on Jan. 4.
Opportunity, its twin, landed on the Meridiani Planum on the opposite
side of the planet Jan. 25. Both rovers still are under operation by
NASA and returning science data.