- Mars has a long history of being misinterpreted, from
conjurings of apparent canals that signaled an alien civilization to the
infamous NASA photo of a supposed giant face. Now a close-up picture of
tiny spheres embedded in a Martian rock has some people seeing fossilized
life.
-
- This alternate, perhaps hopeful view of a picture taken
by NASA's Opportunity Rover and released Monday has been expressed in e-mail
messages to reporters and geologists. Mission scientists anticipated it
and were ready yesterday with a response.
-
- While the spherules, as the small structures are called,
are incredibly interesting, they are not that incredible, according to
Steven Squyres, principal investigator for the Mars Exploration Rover (MER)
project from Cornell University.
-
- "There simply is no reason to promote a biological
origin for these [spherules] when there are so many other, far more probable
ways of making them," Squyres told SPACE.com.
-
- Squyres quoted his former teacher and friend, the late
Carl Sagan, who popularized the phrase, "Extraordinary claims require
extraordinary evidence."
-
- "To claim a finding of fossils on Mars would certainly
be extraordinary," Squyres said, "yet there are many different
and very ordinary ways in which Nature makes spherical objects of this
size by non-biological processes."
-
- Water, maybe
-
- The rover mission is designed to learn whether Mars was
once warmer and wetter -- as most scientists believe -- a place that might
have supported some form of very simple, microbial life. The spherules,
after further investigation, may point in that direction. But water does
not equal life, it only sets the stage.
-
- Asked if, prior to getting these first close-up
images of a Mars rock, he had harbored any hope of finding fossilized life
on Mars, Squyres replied: "Never."
-
- "Even on Earth, which has been a warm and life-friendly
planet for nearly all of its history, macroscopic fossils [the sort that
would show up in a rover image] don't turn up in any real abundance in
the geologic record until about 600 million years ago -- less than 15 percent
of the planet's history," Squyres explained. "To expect that
life could have evolved to that level of complexity in what might have
to be less time, on what has surely been a more hostile planet, would be
asking far too much."
-
- The spherules are a few millimeters in diameter -- much
bigger than a typical bacterium, which would be the sort of thing scientists
would expect to find on the red planet if there is any life there.
-
- The spheres are almost surely of a different composition
than the rock in which they are embedded, a preliminary analysis showed.
Scientists hope to determine what they are made of in coming days with
tests by multiple rover instruments. The tiny beads are thought to have
formed in one of three ways:
-
- * Ash from a volcanic eruption was suspended in the air,
stuck together, and fell from the sky.
-
- * Molten rock from a volcano or a meteor impact froze
in mid-air into glass beads.
-
- * Fluid, possibly water, carried dissolved minerals through
a rock and "precipitated" grains that grew into spheres, through
a process called "concretion."
-
- The last possibility most excites geologists, but more
study is needed to determine which of the hypotheses is correct.
-
- Strange colors
-
- In one strangely colored image of Stone Mountain, the
smallish rock with the outsized name in which the spherules are embedded,
other spherules are seen scattered about in the surrounding soil.
-
- The radical color enhancement -- done purposely to bring
out differences in composition between the rock's primary makeup and that
of the spheres -- gives the spheres an eerie, perhaps even lifelike appearance.
But the colors are not real. In a true-color image of the same scene, the
spheres are unremarkable.
-
- Stone Mountain is part of a modest outcropping roughly
the height of a single stair step. There is a depressed region at its base
-- a shallow crater -- and a higher plateau above. It is not known where
the scattered spherules came from.
-
- "It's impossible to know the pedigree of the ones
that we see in the soil," Squyres said. "Some of them certainly
must have weathered out of the outcrop, but many of them may be from elsewhere,
including materials above the outcrop and outside the crater that we haven't
been to yet."
-
- Squyres had expected to be asked about whether the spherules
were fossils. So he had asked a colleague, Andrew Knoll of Harvard University,
to draft a more lengthy explanation for their non-biological origin.
-
- Not biology
-
- "Some small organisms [on Earth] are spheroidal,
but not all small spheroidal structures are organisms," Knoll writes.
Extraterrestrial structures or chemical signatures can be accepted as biological
"only if we can rule out formation by physical processes -- the idea
being that while life might vary from planet to planet, physics and chemistry
should not."
-
- Knoll continues: "We know that physical processes
make structures like those seen in the images," adding that "we
do not know of any cells on Earth" that would form fossils that look,
in detail, like the structures seen in the Opportunity photograph.
-
- Spherical fossils this big -- a few millimeters in diameter
instead of microscopic -- are relatively rare," Knoll explains. And
cells do not fossilize as whole, solid structures.
-
- Responding to a specific suggestion that the rover had
found small creatures called diatoms, Knoll said: "This is impossible,"
citing several observed characteristics of the spherules that don't match
up.
-
- The spherules are solid or mostly solid, Knoll writes,
with holes interpreted to be small cavities known to geologists as vesicles.
"This is not a likely consequence of biology."
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- http://www.space.com/missionlaunches/opportunity_spheres_040211.html
-
-
- Comment
- From: Gerd Emde
- 2-15-04
-
-
- Can you tell me:
-
- Why doesn't NASA consider fossils as an option for explaining
the
- spheres ?
-
- Some of them do really look nearly exactly like some
fossils found on
- earth:
-
- Compare e.g. the sphere on the following URL:
- http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20040204a/1M
- 129070954EFF0224P2933M2M1_str-B011R1_br.jpg
-
- With the fossils on the following URLs:
- http://www.cretaceousfossils.com/plants/porocystis_globularis.htm
- http://www.iftx.com/oct03.jpg
- http://wardsci.com/category.asp?c=834
- http://www.iftx.com/oct03.jpg
-
- Or compare the Opportunity outcrop structure to the
following image
- showing the layering found in coral fossils on earth:
-
- http://coastal.er.usgs.gov/navassa/geology/fossils4.html
-
-
- So whats's going on a NASA ? Have the geologist overcome
the
- astrobiologists ?
-
- I mean they are searching for water action in mars history
and find
- something that looks very much like fossils and they
don't consider it
- as an option ?
-
- They should try to crack some of the globules by the
RAT or by driving
- over some that are deposited on stones. And then use
the MI. That
- would be an option:
- http://marsrovers.jpl.nasa.gov/gallery/all/1/p/019/1P129879046EFF0352P2266L7M1.HTML
- (spheres on stones)
-
- Maybe we should take action and spread this information
to as many
- people as possible.
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