By BBC News Online science editor Dr David Whitehouse
Liquid carbon dioxide and not water may be responsible for the remarkable gullies pictured on the surface of Mars, according to University of Arizona (UA) scientists.
Last year, astronomers made the dramatic announcement that they had found evidence that water ran on the Martian surface in the recent geological past, and possibly even today.
But looking at the same images of the Red Planet, taken by the Mars Global Surveyor spacecraft, Donald Musselwhite and colleagues publish an alternative hypothesis in the 1 April issue of Geophysical Research Letters.
If it is liquid carbon dioxide rather than water that has been flowing on Mars, it would be a severe blow to the chances of finding primitive life on the planet.
Suspended flow
Space scientists have identified small channels on slopes facing away from mid-day sunlight, with most channels occurring at high latitudes, near Mars' south pole.
Gullies are cut away from sunlight
It has been suggested that water just beneath the surface, warmed perhaps by geothermal activity, periodically bursts out and runs down the slopes and cuts the channels.
If channels are forming today, liquid water may exist in some regions of Mars barely 500 metres beneath the surface.
However, UA scientists think that carbon dioxide (CO2) and not water may be responsible for the gullies. They suggest several reasons why CO2 is a better candidate.
One reason is that most gullies are found in the southern highlands, the oldest and coldest part of the planet, a place where liquid water is least likely to be stable.
Suspended flow
But according to the researchers, the most convincing argument is that gullies always start about 100 m below the top of a cliff or crater. At that depth, the pressure of the rock overhead is just enough for liquid CO2 to be stable, if the temperature is low enough.
"If you have water cutting these gullies, you should see that everywhere, not just at these specific locations. And where is the water coming from? There is not much of it in the Martian atmosphere or on the surface," said Dr Musselwhite.
"What's coming out is liquid CO2 that suddenly vaporises," he maintains.
"As it comes out, it expands very quickly, cools, and actually produces CO2 snow. The snow is suspended in CO2 gas that hasn't solidified yet.
"Together with rock debris, it forms slurry. Geologists call it a 'suspended flow'. Suspended flow acts like a liquid. It doesn't take very much liquid each time to add to gully formation.
"In wintertime, the cliff surface gets so cold that its temperature falls below the freezing point of CO2, which at low pressure goes directly to solid," said Dr Musselwhite.
The researchers believe that as the cold wave moves from the surface, the rock pore space is completely filled in. When spring comes, dry ice warms up and expands. Since all the pore space is filled, pressure builds until the ice turns to liquid.
MY COMMENT:---->
Everybody supports the ET idea and markets it to a
gullible public. This painting above
(from Astronomy Magazine April 1997) proves
nothing. The artist has drawn a tantalizingly
Earth-like planet (allegedly) revolving about a star
called 70 Virginis(an unknown object in the constellation
of Virgo).
But, look, we have a Solar System that was once described
by ignoramuses as well as established scientists as
"teeming with life."
Indeed, Earth does have a biosphere. But it is the
only "world" in the Solar System that does.
[And please, let's not use that W-word "world" for
those clinkers and cratered
monstrosities that populate the rest of our Solar
System and, indeed, the Universe! "World," you know,
is derived from a Germanic root meaning MANKIND,
not lifeless, barren objects in space.
But tell that to Hollywood, to pop-scientists, newspaper
science writers, and to the astro mags!]
Bottom Line:
May I continue to preach??
Why childishly imagine ET
company in space? Let's concentrate our attention
on what we have right down here, on the
third planet out from the Sun that is ideally
situated in a remote corner of the "yolk"
center of our spiraled Milky Way Gallaxy
...We forget that many famous biochemists and
astronomers--and you cannot include an infra-red
pop-scientist like Carl Sagan, et al.,
in this ultra-violet category of serious
scientists--suspect that we may indeed
be alone--yes, in the Universe.
Some scientists maintain that the odds of
developing life in our extremely hostile-to-life
Universe are literally astronomical,
infinitessimally great.
Such renown scientists
as Einstein, Shklovsky, Jeans, Monod, Eddington,
and most recently Astronomy Professdor Brownlee
of the U. of Washington |
et al, argue that we, our planet, are
likely to be alone in having developed life.
The pop-sci crowd will chatter about ET, make
plenty of money on space fantasies.
But they'll never acquire the credentials
of an Einstein or a latter-day Brownlee
Maybe if this thought sank in of Earth's
possible uniqueness, if it were at least "permitted"
--it's not "pop-scientistically correct (P-SC),"
you know, to even suggest such "heresy" of
Earth's uniqueness in possessing a biosphere--
maybe we'd do better with our own very special
Planet.
God knows, the Earth and the creatures dwelling
on it need a lot of undivided attention!
P.S. Meanwhile, don't be taken in by
the argument that, "with all those billions
and billions of Sun-like stars out there,"
countless "Earths" are "bound" to be orbiting them.
Nonsense!
Are any two grains of sand taken from
the myriads of deserts and beaches on Earth
identical? And sand is a very simple silicon
compound. Sand's not a highly-complex single-celled
organism, or like RNA, DNA, a fetus, or, say, a human eye.
Or, about astronomical odds: What if a chimpanzee
sat down at a piano and pounded it for billions
of years--analogous to those "billions of
Sun-like stars"--wouldn't he/she be bound one
fine day to produce a beautiful Bach-like fugue
or prelude or a Beethoven sonata?
You know the answer to that.
And the same odds go for replaying,
say, a relatively simplistic,
9-inning World Series game--even
with the same 18 players, the same day!--
and expecting the same outcomes.
Scientists describe Earth's
doubtlessly unique 4.5-billion-year
evolution--geologically and biologically--
precisely that way. The events were
"well-timed," fortuitous, unique.
Namely, so far as we
know, this "experience" was, is and
always will be unrepeatable--
that is to say, unique. By the way,
this is not necessarily a "religious
argument." Countless religionists going
back to the Middle Ages and the
Renaissance and on up to the present
wrote and write that, on the contrary, they
believe in a "plurality" of worlds Universewide.
The above is not meant as oracular, but
only an appeal to THINK freely
about this question, designed to force my
opinion on anyone, even if I could...
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