Mars Rover Opportunity Makes 'Significant' Finding

Speculation was rife on Monday that space scientists were on the verge of announcing they had discovered evidence that Mars was once a wet and warm planet, possibly capable of sustaining microscopic life forms.

Officials with the National Aeronautics and Space Administration announced that Mars scientists from the Jet Propulsion Laboratory in Pasadena, California, were flying to Washington for a "significant" announcement, but shied away from saying what it would be.

"I can't confirm what they are going to say ... just that it's a significant ... finding," by the rover Opportunity, JPL spokesman Guy Webster said.

But in recent days, scientists have openly spoken of their excitement over finding coarse gray hematite at the Opportunity site, and predicted it would lead to an understanding of how the bedrock the rover is studying was formed and whether water was involved.

The scientists and engineers working with Opportunity and its twin, Spirit, have held all their briefings in Pasadena since the robotic geologists landed on Mars in January.

But major developments in NASA (news - web sites) programs "are typically announced out of (Washington) headquarters," Webster said.

Scheduled to attend the Tuesday briefing were lead rover scientist Steve Squyres, geologist John Grotzinger, chief space exploration scientist Benton Clark, project scientist Joy Crisp, and Jim Garvin, NASA's lead scientist for Mars and the Moon.

Opportunity landed on Jan. 24 in a small crater on the vast flat Meridiani Planum near the planet's equator. It has spent most of its 36 martian days, or sols, studying finely layered bedrock in the crater's wall.

Scientists have been puzzling over whether the layers were formed by wind, volcanic lava flows or water, and if spherical "blueberries" discovered in the rocks were water-related.

In a briefing last week, the Opportunity team said data gathered by the rover's spectrometers and microscopic imager in a flat area of bedrock nicknamed Charlie Flats suggested the presence of gray hematite, which on Earth can form in oxygenated water.

Opportunity's spectrometers also have detected a large deposit of hematite in the surrounding plains.

The science team had planned to compare the spectral signatures of the martian rocks with Earth samples to confirm that the composition was the same.

Evidence of rocks or soil that formed in water would help validate scientists' theories that for the first half of its 4.6 billion-year existence, Mars had plentiful surface water -- even rain and snow -- and possibly, life.

Opportunity and Spirit, now in sol 57 on the other side of the planet, were designed to search for signs of water for at least 90 days, or as long as their solar-powered batteries last.

Here is the bulk of the report you mentioned.. This was cut and pasted from a pdf file so apologies for the narrow columning.
...

TRANSIENT LIQUID WATER AS A MECHANISM FOR INDURATION OF SOIL CRUSTS ON MARS.

Introduction: The Viking and the Mars Exploration
Rover missions observed that the surface of Mars
is encrusted by a thinly cemented layer tagged as
"duricrust" (figure 1).

A hypothesis to explain the
formation of duricrust on Mars should address not only
the potential mechanisms by which these materials
become cemented, but also the textural and compositional
components of cemented Martian soils. Elemental
analyzes at five sites on Mars (Viking [1], Pathfinder
[2] and MER [3]) show that these soils have
sulfur content of up to 4%, and chlorine content of up
to 1%. This is consistent with the presence of sulfates
and halides as mineral cements [4]. For comparison,
the rock "Adirondack" at the MER site, after the exterior
layer was removed, had nearly five times lower
sulfur and chlorine content [3], and the Martian meteorites
have ten times lower sulfur and chlorine content,
showing that the soil is highly enriched in the saltforming
elements compared with rock.

At both MER sites, duricrust textures revealed by
the Microscopic Imager show additional textural features
that need too be considered in any general model
that attempts to account for their origin. These features
include the presence of fine sand-sized grains, some of
which may be aggregates of fine silt and clay, surrounded
by a pervasive light colored material that is
associated with microtubular structures and networks
of microfractures (figure 2). Stereo views of undisturbed
duricrust surfaces reveal rugged microrelief
between 2-3 mm and minimal loose material. Comparisons
of microscopic images of duricrust soils obtain
before and after placement of the Mossbauer
spectrometer indicate differing degrees of compaction
and cementation at the two MER sites.

Here we propose two alternative models to account
for the origin of these crusts, each requiring the action
of transient liquid water films to mediate adhesion and
cementation of grains. Two alternative versions of the
transient water hypothesis are offered, a “top down”
hypothesis that emphasizes the surface deposition of
frost, melting and downward migration of liquid water
and a “bottom up” alternative that proposes the presence
of interstitial ice/brine, with the upward capillary
migration of liquid water. The viability of both of
these models ultimately hinges on the availability of
seasonally transient liquid water for brief periods during
the Martian year.

Duricrust Formation: At the elevation of the
landing sites of all Mars missions to date, including the
Mars Exploration Rovers, the atmospheric pressure lies
above the triple point pressure of liquid water. At
night, soil and rock temperatures are cold enough (e.g.,
about -100C at the Gusev site) to allow a small amount
of water to condense on or between the grains. In the
"top down" model, this deposited frost is warmed by
the daytime temperature rise to form a transient liquid
phase, which migrates downward (assisted by capillary
action), in the process dissolving any salt present. Surface
tension in the liquid pulls the gains together. As
the soil heats further, the water evaporates, and the
remaining salts cement the grains to form the duricrust.
New aeolean dust and sand brings further material to
the site, allowing the surface crust layer to thicken.

In the alternative “bottom up” hypothesis, as sunlight
warms the soil during the day, liquid from a subsoil
brine or ice reservoir is drawn upward by capillary
forces toward the surface, where it evaporates, depositing
any dissolved salts present.

In both cases, dissolved salts and capillary-pore effects
[5] will tend to extend the liquid range of the
water, allowing the process to operate over a wider
range of temperatures.

Repetition of this process over long time spans
could produce a coherent zone of cementation. These
models, which emphasize interactions between the
atmosphere and soils, appear to be quite plausible under
present Martian climatic/atmospheric conditions
and could explain the apparently widespread distribution
of cemented soils on Mars, over a broad range of
elevations latitudes. Variations in the length of time a
transient liquid water phase is present each year would
ultimately determine the presence and thickness of
cementation. However, the thickness of duricrust accumulation
must also be balanced against destructive
processes, such as Aeolian deflation.

This integrated model offers an explanation for the
process of cementation, its widespread distribution and
compositional and textural features of crusts (e.g. presence
of microtubules, a pervasive light-colored “matrix”
observed under MI; the enrichment in sulfur and
chlorine, indicated by APXS). The implied presence of
sulfates and chlorides, both common evaporite minerals
may be compared with potentially analogous settings
on Earth (e.g. cemented playa surfaces and duricrusts
of terrestrial deserts).

Liquid water processes will tend to leech and concentrate
salts in some places, while impacts and aeolian
processes would redistribute them. This would
provide a constant source of salts as newly accreted
fine materials: Unlike Earth, salts on Mars most likely
have not been highly mobilized by water. Salt will
thus be likely to be widely distributed across the surface.
The liquid phase need not occur regularly. The age
of the surface crust is not well constrained, but the
transient water mechanism could operate even if the
conditions for a liquid phase exist only at rare and
widely-separated intervals. Electrostatic agglomeration
may also work to agglomerate micrometer-scale
dust particles into larger units before the cementing.

Differences between the crust at the Gusev and
Meridiani sites yield further evidence and some constraints
for cementation mechanisms. Further constraints
on the origin of these Martian duricrusts should
come from examination of the subsurface that can be
exposed by the rover wheels during driving or during
deeper trenching activities.

The circular pattern on the rock? lol.. A RAT did it! ;-)

http://marsrovers.jpl.nasa.gov/mission/spacecraft_instru_rat.html

Rock Abrasion Tool (RAT)

The Rock Abrasion Tool is a powerful grinder, able to create a hole 45 millimeters (about 2 inches) in diameter and 5 millimeters (0.2 inches) deep into a rock on the Martian surface.

The RAT is located on the arm of the rover and weighs less than 720 grams (about 1.6 lbs). It uses three electric motors to drive rotating grinding teeth into the surface of a rock. Two grinding wheels rotate at high speeds. These wheels also rotate around each other at a much slower speed so that the two grinding wheels sweep the entire cutting area. The RAT is able to grind through hard volcanic rock in about two hours.

Once a fresh surface is exposed, scientists can examine the abraded area in detail using the rover's other science instruments.This means that the interior of a rock may be very different from its exterior. That difference is important to scientists as it may reveal how the rock was formed and the environmental conditions in which it was altered. A rock sitting on the surface of Mars may become covered with dust and will weather, or change in chemical composition from contact with the atmosphere.

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