In what ultimately may be their most significant
discovery yet, Mars scientists say high-resolution
pictures showing layers of sedimentary rock paint a
portrait of an ancient Mars that long ago may have
featured numerous lakes and shallow seas.

“We see distinct, thick layers of rock within
craters and other depressions for which a number of lines
of evidence indicate that they may have formed in lakes
or shallow seas. We have never before had this type of
irrefutable evidence that sedimentary rocks are
widespread on Mars,” said Dr. Michael Malin,
principal investigator for the Mars Orbiter Camera on
NASA’s Mars Global Surveyor spacecraft at Malin Space
Science Systems (MSSS), San Diego, CA. “These images
tell us that early Mars was very dynamic and may have
been a lot more like Earth than many of us had been

Such layered rock structures where there were once
lakes are common on Earth. The pancake-like layers of
sediment compressed and cemented to form a rock record of
the planet’s history.

The regions of sedimentary layers on Mars are spread
out and scattered around the planet. They are most common
within impact craters of Western Arabia Terra, the
inter-crater plains of northern Terra Meridiani, the
chasms of the Valles Marineris, and parts of the
northeastern Hellas Basin rim. The scientists compare the
rock layers on Mars to features seen in the American
Southwest, such as the Grand Canyon and the Painted
Desert of Arizona.

“We caution that the Mars images tell us that the
story is actually quite complicated and yet the
implications are tremendous. Mars has preserved for us,
in its sedimentary rocks, a record of events unlike any
that occur on the planet today,” said Dr. Ken Edgett,
staff scientist at MSSS. “This is changing the way we
think about the early history of Mars — a time perhaps
more than 3.5 billion years ago.”

“On Earth, sedimentary rocks preserve the surface
history of our planet, and within that history, the
fossil record of life. It is reasonable to look for
evidence of past life on Mars in these remarkably similar
sedimentary layers,” said Malin. “What is new in
our work is that Mars has shown us that there are many
more places in which to look, and that these materials
may date back to the earliest times of Martian

Malin added, “I have not previously been a vocal
advocate of the theory that Mars was wet and warm in its
early history. But my earlier view of Mars was really
shaken when I saw our first high-resolution pictures of
Candor Chasma. The nearly identically thick layers would
be almost impossible to create without water.”

As an alternative to lakes, Malin and Edgett suggest
that a denser atmosphere on early Mars could have allowed
greater amounts of windborne dust to settle out on the
surface in ways that would have created the sedimentary

“We have only solved one little piece of a
tremendous puzzle,” Malin said. “There is no
illustration on the box to show us what it is supposed to
look like when it is completed and we are sure most of
the pieces are missing.”

“These latest findings from the Mars Global
Surveyor tell us that more study both from orbit and at
the surface is needed to decipher the tantalizing history
of water on Mars,” said Dr. Jim Garvin, Mars
Exploration Program Scientist at NASA Headquarters.
“Our scientific strategy of following the water by
seeking, conducting in situ studies, and ultimately
sampling will follow up on these latest discoveries about
Mars, and adapt to the new understanding.”

“Mars seems to continually amaze us with
unexpected discoveries,” said Dr. Edward Weiler,
Associate Administrator for Space Science at NASA
Headquarters. “This finding just might be the key to
solving some of the biggest mysteries on Mars, and it
also tells us that our new Mars exploration program needs
the flexibility to follow up in a carefully thought-out

“The finding of layered sedimentary deposits is
something that biologists have been hoping for,” said
Dr. Ken Nealson, director of the Center for Life
Detection at NASA’s Jet Propulsion Laboratory (JPL),
Pasadena, CA. “Perhaps the favorite sites for
biologists to search for fossils or evidence of past life
on Earth are layered lake or oceanic sediments such as in
these sites Malin and Edgett describe.”

The Mars Global Surveyor mission is managed by JPL
for NASA’s Office of Space Science, Washington, DC. Malin
Space Science Systems built and operates the camera
system. Lockheed Martin Astronautics, Denver, CO,
developed and operates the spacecraft.

Images for this release are available at:

Information on the Mars Global Surveyor is available