"Scientists have a crush on Mars, and it’s hard not to look only for things
we want to see," says Mars Exploration Rover scientist, John Grant, from
Washington D.C.’s National Air and Space Museum.

For two years, scientists have wanted to come to Gusev Crater because
pictures and data taken from the Mars Odyssey and Mars Global Surveyor
orbiters have shown evidence that a river may have once flowed into the

Now that Spirit has safely landed in Gusev Crater, scientists must interpret
the right clues that will lead them to understand the geologic processes
that formed the area.

"We’ve talked about Gusev Crater being a dry lake bed for so long, there’s a
danger of getting trapped into believing only in that possibility," warned
Grant. Scientists are forcing themselves to be patient as they begin
gathering clues to figure out how this site formed for sure.

Multiple Explanations for the Same Geologic Observation

"To be trite, you can’t judge a book by its cover," explains Jeff Moersch,
participating scientist from University of Tennessee. There can be multiple
explanations for the same geologic observation. "For example, take a look at
these two pictures on Earth, which look very similar to Spirit’s landing
site on Mars. Look at the shapes of rocks in the pictures, the size of
rocks, the number of rocks in a certain area or the ‘rock distribution’ as
we geologists say," said Moersch.

At first glance, these two places on Earth look similar, and one could
assume the same geologic processes formed the landscapes. However,
geologists have gone to these two places on Earth and discovered they were
formed in different ways.

The Haughton Impact Structure is a crater in the Canadian Arctic and is
roughly 23-million years old. The bottom of the crater flooded and a lake
formed inside the crater. Some of the rocks are scratched in a way that tell
geologists that glaciers probably transported the rocks into the crater

At a glance, the landscape in the Saf Saf area in Egypt looks similar to the
Haughton Impact Structure. The Saf Saf landscape, however, doesn’t have
anything to do with an ancient lake. Although one’s eyes are drawn to the
flat area, similar rock angles, the rock distribution, the light soil, and
further subtle clues observed by geologists revealed that no water ever
flowed where the rocks are scattered in Saf Saf. A river only flowed behind
the rocks in the smoother area up above the rocks.

Without Other Instruments on the Rovers, Scientists Could Argue for Decades
About Gusev’s History

"When I first saw the pictures from Mars, I caught myself saying, ‘I know
this place,’ because it looked like places I had seen on Earth," said Grant.
"But, we’re being very cautious right now because we know we have never seen
this place before, and we must wait for the other instruments such as the
Microscopic Imager and MĖ†ssbauer Spectrometer to reveal better clues about
this landscape," explained Grant. "If we only had pictures of the landing
site, we scientists would argue for decades and maybe never know for sure
how this place formed," said Grant.

Uncovering the Mysteries of Another Planet

"This is like a book that is being read," explained Moersch, and the science
team is working hard not to judge this martian book by its cover. "Like good
detectives, we are looking at everything we can and gathering as many clues
as possible to see if water ever was in this crater long enough to provide
an oasis for life," said Moersch.